Student Pages for Fluid and Dynamics Unit Study:

Science Experiment Lab reportThe Meaning of ForceKinetic Molecular Theorycauseandeffectconsequencesp 38-41 of Physical and Chemical Changes in Matter0001p 38-41 of Physical and Chemical Changes in Matter0002p 38-41 of Physical and Chemical Changes in Matter0003p 38-41 of Physical and Chemical Changes in Matter0004Static Fluids at Rest0001Static Fluids at Rest0002Static Fluids at Rest0003Diffusion GizmoSurface Tension Topic 40001Surface Tension Topic 40002Surface Tension Topic 40003Surface Tension Topic 40004Surface Tension Topic 40005Hydraulic Practice ProblemsFluid_SystemsDensityLabSEExperiment for liquid densityVenn-Diagram-GraphicPlaying with Pascalp 81 of A+ Projects in PhysicsBuoyancy Topic 12 A+ Projects in Physics0001Buoyancy Topic 12 A+ Projects in Physics0002Buoyancy Topic 12 A+ Projects in Physics0003Buoyancy Topic 12 A+ Projects in Physics0004Boyle’s and Charles’ Law worksheetFluid Study Guide

SCIENCE EXPERIMENT WORKSHEET

Name: _______________________________________Grade: ______________________

Project Title: _____________________________________________________________

Statement of the problem (Ask a Testable Question):_____________________________

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Hypothesis (Prediction: what I think will happen): ________________________________

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Plan the Experiment (Rough Draft): __________________________________________

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Equipment and materials (List the Materials): __________________________________

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Procedure (What I plan to do): _______________________________________________

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Record Data and Observations: _____________________________________________

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Interpret Data and Observations: _________________________________________________________________________

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Conclusion (What I found out by doing this experiment): ___________________________

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Apply Findings (How can the results of the experiment be used): ____________________

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Attach notes, measurements, photos, tables or graphs to this sheet.

The Meaning of Force:

Carson has been riding a scooter for almost as long as he can remember. As you can see, he’s really good at it. He can even do tricks in the air. It takes a lot of practice to be able to control a scooter like this. Carson automatically applies just the right forces to control his scooter.  

Defining Force Force is defined as a push or pull acting on an object. There are several fundamental forces in the universe, including the force of gravity, electromagnetic force, and weak and strong nuclear forces. When it comes to the motion of everyday objects, however,

the forces of interest include mainly gravity, friction, and applied force. Applied force is force that a person or thing applies to an object.

Q: What forces act on Carson’s scooter?

A: Gravity, friction, and applied forces all act on Carson’s scooter. Gravity keeps pulling both Carson and the scooter toward the ground. Friction between the wheels of the scooter and the ground prevent the scooter from sliding but also slow it down. In addition, Carson applies forces to his scooter to control its speed and direction.

Force and Motion Forces cause all motions. Everytime the motion of an object changes, it’s because a force has been applied to it. Force can cause a stationary object to start moving or a moving object to change its speed or direction or both. A change in the speed or direction of an object is called acceleration. Look at Carson’s brother Colton in the Figure below. He’s getting his scooter started by pushing off with his foot. The force he applies to the ground with his foot starts the scooter moving in the opposite direction. The harder he pushes against the ground, the faster the scooter will go.

How much an object accelerates when a force is applied to it depends not only on the strength of the force but also on the object’s mass. For example, a heavier scooter would be harder to accelerate. Colton would have to push with more force to start it moving and move it faster. You can explore the how force, mass, and acceleration are related by doing the activity at this URL:

Q: What units do you think are used to measure force?

A: The SI unit for force is the Newton (N). A Newton is the force needed to cause a mass of 1 kilogram to accelerate at 1 m/s2, so a Newton equals 1 kg · m/s2. The Newton was named for the scientist Sir Isaac Newton, who is famous for his laws of motion and gravity.

Summary · Force is defined as a push or pull acting on an object. Forces include gravity,

friction, and applied force.

· Force causes changes in the speed or direction of motion. These changes are

called acceleration.

· The SI unit for force is the Newton (N).

From CK-12 Physical Science Concepts for Middle School

The Meaning of ForceA force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction.

For simplicity sake, all forces (interactions) between objects can be placed into two broad categories:

·contact forces, and·forces resulting from action-at-a-distance

Contact forces are those types of forces that result when the two interacting objects are perceived to be physically contacting each other. Examples of contact forces include frictional forces, tensional forces, normal forces, air resistance forces, and applied forces.

Action-at-a-distance forces are those types of forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation. Examples of action-at-a-distance forces include gravitational forces. For example, the sun and planets exert a gravitational pull on each other despite their large spatial separation. Even when your feet leave the earth and you are no longer in physical contact with the earth, there is a gravitational pull between you and the Earth. Electric forces are action-at-a-distance forces. For example, the protons in the nucleus of an atom and the electrons outside the nucleus experience an electrical pull towards each other despite their small spatial separation. And magnetic forces are action-at-a-distance forces. For example, two magnets can exert a magnetic pull on each other even when separated by a distance of a few centimeters.

Examples of contact and action-at-distance forces are listed in the table below.

Contact Forces Action-at-a-Distance ForcesFrictional Force Gravitational ForceTension Force Electrical ForceNormal Force Magnetic Force

Air Resistance Force

Applied ForceSpring Force

Force is a quantity that is measured using the standard metric unit known as the Newton. A Newton is abbreviated by an "N." To say "10.0 N" means 10.0 Newton of force. One Newton is the amount of force required to give a 1-kg mass an acceleration of 1 m/s/s.

KINETIC MOLECULAR THEORY

When you have completed this lesson, you should be able to use the Kinetic Molecular Theory to explain the properties of gases, liquids and solids.

Assumptions of theoryThe Kinetic Theory of Matter is a prediction of how matter should behave, based on certain assumptions and approximations. The assumptions are made from observations and experiments, such as the fact that materials consist of small molecules or atoms. Approximations are made to keep the theory from being too complex. One assumption is that the size of the particles is so small that it can be considered a point. Chemists use the Kinetic Molecular Theory to explain why matter, especially gases, behaves as it does. The major points of the theory are:

1. Matter consists of small particles - matter consists of a large number a very small particles—either individual atoms or molecules.

2. Large separation or spaces between particles · In a gas, the separation between particles is much larger than the particles

themselves, such that there are no attractive or repulsive forces between the molecules.

· In a liquid, the particles are still far apart, but now they are close enough that attractive forces confine the material to the shape of its container.

· In a solid, the particles are so close that the forces of attraction confine the material to a specific shape.

3. The particles are in constant motion · In gases, the movement of the particles is assumed to be random and free. The

particles are in constant straight-line motion and only change direction when they collide with another particle or the sides of the container.

· In liquids, the movement is somewhat constrained by the volume of the liquid. · In solids, the motion of the particles is severely constrained to a small area, in

order for the solid to maintain its shape. · The velocity of each particle determines its kinetic energy.

4. There are forces of attraction between the particles. In gases, these forces are negligible.

5. Collisions transfer energyThe numerous particles often collide with each other. Also, if a gas or liquid is confined in a container, the particles collide with the particles that make up the walls of a

container. Also, atoms and molecules have a discrete size, some small and some large. But charting the collisions of such particles would again make the theory too complex. Thus an approximation is made to say the size of the particles is a simple point, especially compared to the distances involved.6. No Energy Change (ie. Elastic) Collisions

According to the Kinetic Molecular Theory, the particles of a gas are constantly moving in random straight-line motion. If the gas particles are in a container, the particles must eventually collide with the sides of the container or other gas particles. When the particles collide with the sides of the container, they exert a force upon the container’s walls. We call this force gas pressure. Pressure is defined as force per unit area. When the particles collide there are 3 possible options that can occur in these collisions:

1. The collision could result in a loss of energy. That is, the energy the particle contains before the collision is greater than after the collision. If this were true, the particles would eventually slow down and the pressure would decrease.

2. If the particles have more energy after the collision than before, the particles would gain energy due to collisions. If this were true, the particles would speed up and the pressure would increase.

3. If the energy of the particles before and after the collisions were equal the pressure inside the container would remain constant, at a constant temperature.

Let us examine these three options by studying a propane barbeque tank. If a propane tank is not used, the tank maintains its pressure (force of gas on the sides of the tank) providing the amount of gas remains constant (that is, there are no leaks) and the temperature remains unchanged. If the particles gained energy with every collision, the force of each collision would increase, increasing the pressure. If the particles lost energy with every collision, the force of each collision would eventually decrease, resulting in a lower pressure. This means that options one and two can not be valid options for collisions and actual events are more reflected by option three.According to the Kinetic Molecular Theory collisions between particles and between particles and their container are elastic. This means there is no loss of energy. This is illustrated in the diagrams below.

In Figure 1, the bouncing ball loses energy with each bounce and as a result the force of the bounce decreases as does the height of its bounce. In Figure 2, the bounces are perfectly elastic. There is no loss of energy, so the ball returns to its original height.

Thus, an assumption is that the particles transfer energy in a collision with no net energy change. That means the collisions between the particles are perfectly elastic and no energy is gained or lost during the collision. This follows the Law of the Conservation of Energy. In reality, when atoms or molecules collide, energy may be given off in the form of electromagnetic radiation, but this energy is so small that its effect is negligible and is not taken into account to simplify things.

Thermal energy and heat flowThe motion of a particle determines its kinetic energy, according to the equationKE = ½mv²where

· KE is the kinetic energy of the particle· m is its mass· v² is the square of its velocity

The total internal kinetic energy of all the particles is called its thermal energy. The temperature of an object or collection of matter is the average kinetic energy of the particles. As the temperature increases, the speed of the particles increases. As the temperature decreases, the particles' speed decreases. That is, the kinetic energy of the particles increases with increasing temperature and decreases with decreasing temperature.Heat is the transfer of thermal energy from an object of higher temperature to one of lower temperature. For example, an object feels warm or hot if its temperature is higher than your skin temperature. The Kinetic Theory of Matter explains heat transfer by conduction, where thermal energy seems to move through a material, warming up cooler areas. This is called heat transfer or heat flow.

Collisions transfer energy The Kinetic Theory of Matter states that the material's particles have greater kinetic energy and are moving faster at higher temperatures. When a fast moving particle collides with a slower moving particle, it transfers some of its energy to the slower moving particle, increasing the speed of that particle.If that particle then collides with another particle that is moving faster, its speed will be increased even more. But if it hits a slow moving particle, then it will speed up the third particle.With billions of moving particles colliding into each other, an area of high energy or high heat will slowly diffuse across the material, making other areas warm too. By the Conservation of Energy, the total energy or total heat of the object will remain the same, but the heat will be evenly distributed throughout the object.

Rate of transferThe rate at which the kinetic or thermal energy is transferred from one particle to another depends on the separation of the particles and their freedom to move. In a gas, the particles are allowed to move freely, but their separation distance is great, so heat or energy transfer is slow. In a liquid, the heat transfer by conduction is faster because the particles are closer together.In a solid, the molecules are constrained into a specific location within the material. Although the particles are closer together than in liquids, the constraints in some materials actually prevent the transfer of heat energy. A good example of that is in wood.

TemperatureOne important result of the kinetic theory is that the average molecular kinetic energy is proportional to the absolute temperature of the material. Absolute temperature is measured in the Kelvin scale, which is about 273 degrees lower than the comparable Celsius degree. But in general, you can say that temperature is the measurement of the average internal kinetic energy of the material or object.

SummaryThe Kinetic Theory of Matter states that matter is composed of a large number of small particles that are in constant motion. It also assumes that particles are small and widely separated. They collide and exchange energy. The theory helps explain the flow or transfer of heat and the relationship between pressure, temperature and volume properties of gases.

How Kinetic Molecular Theory Relates to The States of MatterGases

Using the kinetic molecular theory and the physical characteristics discussed in the previous lesson, we can develop a particulate model for gases. Gases are easily compressed, as is demonstrated by air compressors. This means the particles of a gas must be very far apart. Gases also have low densities, suggesting the particles are quite loosely packed. In fact, in a container of gas, less than one-tenth of one percent of its total volume is occupied by gas particles. This means more than 99.9% of a container of gas is empty space!Gases will fill any volume they are given and diffusion is very easy. A good example is that an air freshener or perfume eventually moves throughout a room, even if sprayed in a corner. If gases fill any container, the forces of attraction between the particles must be very low. If the forces of attraction were large, the particles would be held in a defined space like solids and liquids. This means the particles of a gas move freely in rapid straight-line motion and their motion is rarely changed by the interference of other gas particles.The freedom of motion also suggests that the forces of attraction, or repulsion, between individual gas particles is minimal or non-existent.

Solids

Since solids are not easily compressed, the particles must be so close together that they cannot be easily forced any closer. The high density of most solids also suggests there are more particles per unit volume than both liquids and gases.

The definite shape and volume of solids also suggests that the particles are held together quite tightly and must not move very much, in fact they probably just vibrate in place. Therefore, the forces of attraction between particles or intermolecular forces (imfs) in a solid must be very high. It is important to note that forces of attraction and chemical bonds are not the same. In order for diffusion to occur, particles must easily move through the matter. Since the particles in a solid are very close together, other particles cannot easily move through and mingle with solid particles.Solids come in two main forms: crystalline and amorphous. Crystalline solids, or crystals, have molecules, ions or atoms in an orderly, geometric, three-dimensional arrangement. Each element and compound has a unique crystal structure. A simple crystal structure is shown at the right.

A covalent network solid has atoms covalently bonded in a crystal. Examples of covalent networks are graphite and diamond, where carbon atoms are arranged in a regular repeating structure. The covalent bonds make it very difficult to separate the individual atoms.

Diamond GraphiteIonic solids have a regular arrangement of positive and negative ions in a crystal. The ions are held together by electrostatic forces. Each individual ion is held in the crystal lattice by several other ions.

Molecular solids such as sugar or ice, have molecules as the lattice points. The molecules are held together by intermolecular forces. These forces can be strong or weak, but are usually weaker than covalent solids and ionic solids.The crystal arrangement holds the individual particles of the solid into that form, so the only movement that is possible is vibrational. As the temperature increases, random motion increases causing the particles to move further apart, decreasing strength of the forces holding the solid together. Amorphous solids have particles that are in no particular order so they can change shape under certain circumstances (eg. Rubber, wax, glass).

Liquids

Liquids are not easily compressed. The use of hydraulics supports this prediction. Front-end loaders, dump trucks, etc. lift heavy loads with a column of liquid. If liquids were compressible, this would not be possible because the force of the load would compress the liquid. Since liquids are not compressed easily and they have relatively high density, the particles must still be very close together and densely packed.

Liquids do not have a definite shape. This means the forces of attraction between liquid particles must not be as strong as those in a solid. The forces are strong enough to hold the particles in an open container so the volume can be measured, but not strong enough to hold the particles in a constant shape.If the particles in a liquid are not held in a constant shape, the particles must be moving around more than the particles of a solid. The particles of a liquid are able to just slide past each other.The particles of a liquid are not much further apart than in a solid. There is just enough room for them to slide past each other. They must be close together or they would be easier to compress.Since the particles of a liquid have spaces between them, other particles are able to move between the liquid particles. As liquid particles move, they collide with each other and other particles. These collisions push other particles through the liquid.Other Types of Matter

Not all forms of matter can be readily described as solids, liquids or gases. Plasma is considered a fourth phase. It is extremely rare on earth but makes up 99% of known matter in the universe (stars). Similar to a gas, particles move with extremely high energy and speeds, so that the electrons shoot off separately from the nucleus of the atoms. Plasma is seen on earth in lightning, fire, aurora borealis and solar matter. Liquid crystals are substances with particles that lose the fixed position of solid particles in only one or two dimensions when they are heated or an electric current is passed through them. The forces between the particles in a liquid crystal are weak, and their arrangement is easily disrupted. “LCDs” or liquid crystal displays are used in watches, thermometers, calculators, laptops and televisionsAmorphous (Greek for “without form”) materials have an irregular arrangement of particles. These substances do not have a definite melting point and include many

materials, some examples of which are: peanut butter, candles, cotton candy, glass, rubber, plastic and asphalt. Amorphous carbon is produced from the decomposition of carbon compounds. When animal bones decompose, bone black is produced. It is used as a pigment and in the refining of sugars. The decomposition of coal produces the coke that is used in dry cell batteries. The figures below show the regular crystal structure of quartz and the amorphous structure of glass.

Quartz Glass (Amorphous)

Summary:

In this lesson we have learned:· the 4 states of matter are solid, liquid, gas and plasma.· particles of a solid have strong intermolecular forces, very little space between

the particles and the particles can only vibrate.· crystalline solids have particles arranged in a regular pattern· particles in amorphous solids do not have a regular pattern· crystalline solids can be atomic, molecular or ionic.· particles of liquids have strong intermolecular forces (but weaker than solids), are

further apart than solids, and are able to slide past each other.·

·

Adapted from Transcona Community Learning Centre’s document for CHEM 30S (August 2006) and from “Kinetic Theory of Matter by Ron Kurtus at http://www.school-for-champions.com/science/matter_kinetic_theory.htmPictures from Discovery Education’s summary of fluids

Diffusion Gizmo:

Vignette

Can you Diffuse the Situation?

Pam Hancock Larson Unit Notes

Grade: 8Learning Goals: Students will understand that (1) the cell membrane helps regulate the transfer of materials in and out of the cell through processes called osmosis and diffusion; (2) these processes allow most small molecules to cross the membrane by moving materials from high to low concentrations (3) the transport and exchange of nutrient and waste molecules are important to the survival of the cell and the organism; (4) osmosis and diffusion are affected by concentration, molecule mass and size, temperature, and various membrane barriers, like pore size.

National Science Education Standard: Content Standard C: 5-8, Life Science: Cells carry on the many functions needed to sustain life. They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to provide energy for the work that cells do and to make the materials that a cell or an organism needs. (National Research Council 1996)

Missouri Grade Level Expectations: Strand 3: Characteristic and Interaction of Living Organisms, #1C. Cells are the fundamental units of structure and function of all living things, Grade 6a. Recognize all organisms are composed of cells, the fundamental units of life, which carry on all life processes Strand 3: #2A. The cell contains a set of structures called organelles that interact to carry out life processes through physical and chemical means, Grade 8a. Recognize the cell membrane helps regulate the transfer of materials in and out of the cell Strand 3: #2C. Complex multicellular organisms have systems that interact to carry out life processes through physical and chemical means, Grade 8e. Identify the importance of the transport and exchange of nutrient and waste molecules to the survival of the cell and organism Strand 7: Scientific Inquiry, #1A. Scientific inquiry includes the ability of students to formulate a testable question and explanation, and to select appropriate investigative methods in order to obtain evidence relevant to the explanation, Grade 8a. Formulate testable questions and hypotheses, b. Recognize the importance of the independent variable, dependent variables,

control of constants, and multiple trials to the design of a valid experiment, c. Design and conduct a valid experiment Strand 7: #1E. The nature of science relies upon communication of results and justification of explanations, Grade 8a. Communicate the procedures and results of investigations and explanations through: oral presentations, drawings, data tables, graphs, and writingsAssessment Strategies: Engage: science journal, observations, group discussion

Explore: team log and questionnaire, scientists’ meeting

Explain: Gizmo assessment questions, concept map

Elaborate: 4-question strategy, experimental design

Evaluate: team presentation, constructed response items

Note: This vignette is partially based on actual classroom experiences with a grade 8 class from Tarkio R-1 school district. There are parts that have been changed and updated, which therefore differ from the actual instruction and assessment used in this classroom. Some parts are totally new ideas written for an Assessment class and have not been tested in an actual classroom setting.

Vignette

EngageAsk students, “Have you ever been woken up on Saturday or Sunday morning by the smell of your mother or father cooking breakfast?” or “Have you ever smelled perfume or cologne on someone before they actually walked by you?” Many answers ensued, including ones about what families eat for breakfast or don’t eat for breakfast. And of course, stories about someone who wears too much perfume or cologne. Not quite what I was headed for, but we’d get there.

I asked two students to hand out science journals as I got my supplies ready for the demonstration. “Let’s see what happens with these materials. Record any observations in your journals as you watch my demonstration.” I filled a small beaker with cold water, placed it on a table, and allowed it to sit until there was no movement in the water. Then, using a large plastic dropper I added one drop of blue food coloring to the water. We observed the water for about five minutes or until we could no longer see any changes. Students wrote down any observations as we watched the water and food coloring. I also instructed students to explain in their journals what they saw happen and why they thought it happened that way.

As a class, we discussed some of their observations and guesses about what they thought had caused the movement of the food coloring. I also posed questions to the class, such as “How would the results of the activity be different if we used a larger amount of water, or a larger drop

of food coloring?” I used this class discussion as an assessment for determining previous knowledge or misconceptions by the students.

ExploreEach student team was given one of three labs to perform, showing different types of cells undergoing diffusion or osmosis; one in a make-believe cell, one in an animal cell, and one in a plant cell. Each team kept a log of the observations and the data they collected for each day of testing in their science journals. One team (A) was given cornstarch and water to mix together and pour into a plastic bag after measuring the volume of the mixture, keeping a small amount in a test tube. They placed the plastic bag into a beaker half full of water and twenty drops of iodine after measuring the volume. They also kept a small sample of the water/iodine mixture in a small test tube. Two teams (B, C) were given a raw egg to place into a closed container of 250 milliliters of vinegar, after measuring the circumference of the egg and the volume of the vinegar. Two more teams (D, E) were instructed to use an Elodea leaf to make a wet mount and to observe the leaf under the microscope. After making observations of the leaf, the team added a drop of salt water under one side of the cover slip and used a paper towel on the other side to draw the salt water through the specimen. They recorded their observations and some drew pictures of what the cell looked like with the salt water. All teams made entries into their logs in their science journal and continued their testing the next class period.

On the second day of testing, team A compared the color of the solution outside the plastic bag to the solution kept in the test tube and the color of the solution inside the plastic bag to the test tube kept of that solution. They also measured the volume of the solution inside and outside the bag and made comparisons to the first day log. Teams B and C removed the egg from the jar, measured its circumference and the volume of the vinegar left in the jar. They then rinsed the egg and placed it into a container of 250 milliliters of corn syrup. Teams D and E made another wet mount of the Elodea leaf but this time after adding salt water, they added distilled water to one side and drew it through the slide with a paper towel. All teams, once again, made entries into their logs and completed their testing or recording the next class period.

On the final day, the only teams with data yet to collect were teams D and E. They measured the circumference of their egg and the final volume of corn syrup in the container. After each team completed their logs, I handed out a questionnaire for each team to complete related to their specific lab. These included such questions as: (A); Was your cell model permeable or impermeable to iodine? To starch?, How might the size of the pores in your membrane compare to the size of the starch molecules? To the iodine?, What might have caused the movement of the molecules? (B, C); Where did the vinegar go?, Why did the egg shrink when put into corn syrup?, What determined whether the egg got bigger or smaller? What might have caused the movement of the molecules? (D, E); How did the plant cell change after

osmosis each time? What caused the changes? Why didn’t the cell wall change during the procedure?

After giving ample time to complete the questionnaire, we reassembled and held a scientists’ meeting. Each team explained their lab activity and the data they had collected. They also used information from their questionnaire answers to relate the data to the concept they had tested. In maintaining seamless assessment, this allowed me to assess understanding of the concepts at this phase and helped me to know what to focus on in the explain phase.

ExplainI started the explain phase by using two Gizmo simulations found at (www.explorelearning.com). I began with the Gizmo called “osmosis” because it showed the movement of molecules into and out of a cell and introduced students to the vocabulary associated with cell transport. As we completed the Gizmo together, students filled in their exploration guide that accompanies the Gizmo. As going through the steps, we discussed such things as higher to lower concentration, movement of water in osmosis, solute, solvent, and equilibrium. The Gizmo called “diffusion” was completed next, once again as a class. It shows the effect of variables on the rate of diffusion and osmosis and allows for a perfect transition into the elaborate phase. The Gizmos also have an assessment quiz at the bottom of each one. I used these to have each individual student check their answers, so I could look at them overnight and determine how the learning was progressing and what they had gotten out of the explain.

Upon completion of the Gizmos, we brainstormed as a class to produce words that have to do with transport across a cell membrane such as; osmosis, diffusion, equilibrium, concentration, solute, solvent, temperature, etc.. As I wrote them on the board, students were to begin thinking about structuring a concept map using these terms and others they could think of on their own. After walking around the room and noticing if students had completed the concept map, I allowed them to reconstruct their map onto transparency paper to show to the class. Most students were happy to do this and excited to get to use the overhead projector. As we worked through several concept maps, I could tell that students seemed to understand the concepts and decided to collect the maps to look at individually for reteaching purposes the next day or with individual students. My overall feeling from our discussion was that the students were ready to move to the elaboration phase and go deeper into their understanding of cell transport.

ElaborateDuring earlier class discussions, students noticed and asked questions like: “What would happen if I heated up the solution?”, or “What if I used this liquid instead of that one?”, or “What if I used a higher concentration of this?” So, for the elaborate, I decide to give them a chance to experiment with any variable they wanted to on any of the three lab activities from the explore phase. Each team filled out a 4-Question Strategy template (Cothran, 2000) into their science journals. This time it was a little different since they already knew the basic materials they would use and what action they wanted to measure, but they could still use the template to give me an idea of what variables they had decided to use and change. As teams filled out the template, I filtered through the room making sure that all teams were testing something different. I felt this was important because I wanted all students to gain a deeper understanding of all the

possibilities that could affect cell transport such as concentration, type of material, temperature, time, etc. Once all teams had completed a 4-Question Strategy we had five really interesting experiments with different variables that affect cell transport. Examples included; how other liquids will travel across the cell membrane of the egg, what will other solutions do to the plant cell, how will the concentration of the iodine affect the starch solution, will increasing the temperature of the solution outside affect the time it takes for the reaction to occur, and will decreasing the concentration of the salt in the water change how the cell reacts.

The teams continued to the testing portion of the elaborate phase by filling out the top of an Experimental Design template (Cothran, 2000) into their science journals. It asks for the testable question, hypothesis, independent and dependent variables, constants, and a data table set-up. Once I had filtered through the classroom making sure that each team was on the right track, the teams began testing. Since each team was doing something different it was a little crazy at first, but once they all had the materials they needed every team was off and running. All teams completed their testing with few problems and were able to fill in the rest of their Experimental Design template with a graph and conclusion. The Experimental Design information is what will be used for the evaluate phase. It is also the form of seamless assessment for this phase that continues right into the next.

EvaluateThe first part of the evaluate phase included a team presentation of data and conclusions from the explore phase. Teams were given an entire class period to organize their data and make decisions about the presentation format they would use. They could present using power point, posters, drawings, or demonstrations, instead of just standing and delivering information. I encouraged them to involve their classmates in their presentation and showed them a copy of the rubric I had developed. Most teams chose a power point presentation and did a very clever job of making the slide show interesting and entertaining, as well as informative. All teams came to the desired conclusions about concentration, temperature, type of solution, and size of particles and their effect on the rate of diffusion or osmosis. Once all teams had presented, I used the opportunity to talk to students about how much they had learned. We discussed what types of things we had talked about during the engage phase compared to what they were able to discuss now. Most of the assessment that had been used, up to this point, had incorporated team discussions and products or class discussions and science journal observations. This information allowed me to plan the following phases, but did not provide give me much information about individual student learning. So, I decided to give each student a short constructed response quiz that would assess individual understanding. The first prompts were simple recall questions that related to what we had done throughout the phases.

Your mother sprays an air freshener in the kitchen as she is cleaning. Within a few seconds you are able to smell the air freshener, even though you are in the living room watching a movie. Name the process that allows you to smell the freshener and its effect upon the molecules in the kitchen and the living room.

Your teacher places a piece of potato into a cup of water with blue food coloring in it. Predict what will happen to the potato after sitting overnight in the blue water. Describe

what would happen if you increased the concentration of the food coloring and let the potato sit for a second night.

The last prompts were designed to assess deeper understanding and application to real-life situations.

Suppose a permeable membrane separates salt solutions with concentrations of 5 g/L and 7 g/L. Which way will the salt diffuse across the membrane? Explain why.Another selectively permeable membrane separates solutions A and B. The concentration of water in solution A is 75%, while in solution B the water concentration is 80%. Describe the movement of water molecules.Compare and contrast the processes described and the movement of molecules in the two scenarios.

The fifth grade teacher has asked us to help explain osmosis and diffusion to his class. Write an explanation of what you would tell the class. Include what osmosis and diffusion are, how they work in the environment and in the cell, and the types of variables that can affect the rate of each. You may include drawings to show the class if it will help with your explanation.

Based on what you have learned from studying the diffusion of different concentrations, what might be one reason that a person with a breathing disease might wear an oxygen mask? Explain.

Even after all the seamless assessment used throughout the 5E Model, I still noticedfrom the constructed response questions, that some students had not gained a deep understanding about the effects of the differing variables on cell transport. This had not been noticed throughout the lesson due to most of the assessments including teams and or the entire class. I decided that in addition to group assessments, I would use individual assessments more often as the phases progressed. This should help my assessment of individuals and groups at the same time, and help lead to better understanding by all students and better seamless assessment throughout the entire lesson.

Notes1. 4-Question Strategy and Experiment Design templates are common strategies used in inquiry labs for students. The templates can be found in Students and Research, by Julia H. Cothran, Edition 3, 2000, pages 31, 39, and 41.

Hydraulic Practice Problems (Pascal’s Principle ∆P = F

Change in P = F1 = F2

A1 A2

1. The large piston in a hydraulic lift has an area of 250 cm2. What force must be applied to the small piston with an area of 25 cm2 in order to raise a car of mass 1500 kg?

2. A trash compactor pushes down with a force of 500 N on a 3 cm2 input piston, causing a force of 30,000 N to crush the trash. What is the area of the output piston that crushes the trash?

3. When the button of a trash compactor is pushed, a force of 350 N pushes down on a radius of 1.3 cm for the input piston (use area of a circle to calculate area), creating a force of 22,076 N to crush the trash. What is the area of the piston that crushes the trash?

∆P = F1 = F2

A1 A2

4. Johnny the auto mechanic is raising a 1200 kg car on her hydraulic lift so that she can work underneath. If the area of the input piston is 12 cm2, while the output piston has an area of 700 cm2, what force must be exerted on the input piston to lift the car?

5. Marc’s favorite ride at Busch Gardens is the Flying Umbrella, which is lifted by a hydraulic jack. The operator activates the ride by applying a force of 72N to a 30cm2 cylindrical piston, which holds the 20,000N ride off the ground. What is the area of the piston that holds the ride?

6. Mr. Short is raising a 2000kg car on his hydraulic lift. If the area of the input piston is 9cm2,

while the area of the output piston is 630 cm2, what force must be exerted on the input piston to lift the car?

7.8.Jenny McKay Fluid SystemsGary Chan

Overview:

PLO: Students will be able to recognize similarities between natural and constructed fluid systems (e.g. hydraulic, pneumatic).

This topic discusses what happens when fluids are under pressure (forces, which lead to movement). Several examples that utilize this concept are then presented in the form of constructed fluid systems and natural fluid systems. To successfully understand this topic, students should learn why compressed fluids result in motion. Students also need to apply this idea to explain examples of fluid systems, and compare the similar functions that exist between different fluid systems.

Fluids Under Pressure:· Fluids move from areas of high pressure to areas of low pressure· The deeper you are in a fluid, the higher the pressure will be (as you dive

deeper, water pressure increases; at sea level, atmospheric pressure is higher than at the top of a mountain)

· Objects in fluids will rise or sink because of density differences (called buoyancy) – if an object has a lower density than the surrounding fluid, it will rise, or if it has a higher density than the surrounding fluid, it will sink.

Constucted Fluid Systems: Man-made systems that use the concept of fluid pressure in applications.· Submarines – take in water (increase density) to sink; expel water using

compressed air (decrease density) to rise· Hydraulic systems:

o Use the pressure of liquids to do work.o Use pumps to move liquids.o Pressure applied at one point in a fluid is transmitted equally through the

entire system (squeezing an enclosed liquid creates static pressure…this is why, wherever you squeeze a tube of toothpaste, it will still come out – squeezing creates a static pressure which is transmitted from wherever it’s created throughout the entire tube).

o This is how car brakes work – when you press on the brake pedal, it squeezes the fluid in your brake line, which transmits pressure (and force) to the brakes.

o This is also used in hydraulic lifts (remember: P=F/A) – when a force is applied to a small area, it creates some pressure, P, which is then transferred to the larger area...the pressure at the large area is also P, so with a larger area, it means the force is also proportionally larger (F=PA)

o Also used to power the stage for “Ka” (Cirque du Soleil show)o Many bends in the system of dirty/blocked pipes will decrease the

efficiency of the system.· Pneumatic systems:

o Use gas under pressureo Use compressors to create pressure and move gas.o When gases move, the faster they move, the lower the pressure

perpendicular to the direction of movement will be. (i.e. a plane wing – the distance air moves over the top of the wing is farther than the distance moved over the bottom of the wing, causing it to move faster, the pressure above the wing to be lower, and the plane to rise). (Can show this concept to students by having them blow across the top of a piece of paper – it will rise.)

o Used in vacuum cleaners – a fan spins at high speed creating an area of low pressure, causing the air from outside to move into the vacuum (from the high pressure outside of the vacuum to the low pressure inside of the vacuum) carrying the dirt with it

o If air flow is blocked (i.e. filter is dirty), a pneumatic system won’t work as well.

Natural Fluid Systems: Naturally-occurring systems that apply the concept of fluid pressure.· Weather – thunderstorms and hurricanes are formed in part by pressure

differences· Volcano – when magma flowing to the surface is blocked, it builds up

pressure until eruption.· Human Body:

o Ears “pop” as you climb up in altitude (or decrease in altitude). The pressure outside is less than the pressure inside your body. Your eardrum pops to equalize the pressure. This is why some people find taking off and landing in planes uncomfortable.

o Water is a fluid in your body. Pressure keeps fluids moving in living things.

o Circulatory System A type of hydraulic system because the fluid is blood, a liquid Heart is the pump. Blood vessels are the pipelines. Blood

constantly moves through the system due to the beating heart. (When the heart beats it creates a higher pressure in

the oxygenated blood, which causes it to travel to the rest of your body.)

Blood Pressure is the force of the blood on the walls of the blood vessels. Clogged arteries (obesity) or narrow arteries (smoking) increase blood pressure because the heart has to work harder to keep the blood moving.

o Respiratory System Inhale: diaphragm goes down, chest cavity expands, creating

a low pressure area inside the lungs. Air from the outside (at a higher pressure) then rushes in.

Exhale: diaphragm goes up, chest cavity contracts, increasing pressure in the lungs. Air then goes out because the air outside is now at a lower pressure than the air inside.

Clogged airways (smoke, pollution, dust), swollen airways (bacteria, infections) and narrow airways (asthma) affect the efficiency of the system.

Motivator:· “Blue Fountain” – from p. 319 of BC Science 8

o Fill a glass cup about half full of cold water with blue food colouring.

o Create a closed system by making the canning jar and lid as in Task Card #11 in TOPS #16 Pressure. Put a small amount of water in the bottom of the canning jar, without the lid. Heat in microwave until it starts boiling.

o Put the lid with the tubing onto the canning jar and close it tightly to seal it.

o Use heat resistant gloves to invert the canning jar and insert the end of the tubing into the glass. Blue water will be pulled up into the flask, making a fountain.

A Notable Quote:· Pilots and passengers are reminded that opening doors or windows in

order to touch the face of God may result in loss of cabin pressure.

Closure / Assessment:· Make a Venn diagram to compare constructed and natural fluid systems,

hydraulic and pneumatic systems· Extension: Research another hydraulic or pneumatic system and do a one

page assignment showing a diagram and paragraph to explain how it works.

Name: ______________________________________ Date: ________________________

Student Exploration: Density Laboratory

Vocabulary: buoyancy, density, graduated cylinder, mass, matter, scale, volume

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

1. Of the objects below, circle the ones you think would float in water.

2. Why do some objects float, while others sink? ____________________________________

_________________________________________________________________________

_________________________________________________________________________

Gizmo Warm-upThe Density Laboratory Gizmo™ allows you to measure a variety of objects, then drop them in water (or other liquid) to see if they sink or float.

1. An object’s mass is the amount of matter it contains. The mass of an object can be measured with a calibrated scale like the one shown in the Gizmo. Drag the first object onto the Scale. (This is object 1.)

What is the mass of object 1? _______________________________

2. An object’s volume is the amount of space it takes up. The volume of an irregular object can be measured by how much water it displaces in a graduated cylinder. Place object 1 into the Graduated Cylinder.

What is the volume of object 1? _____________________________

Note: While milliliters (mL) are used to measure liquid volumes, the equivalent unit cubic centimeters (cm3) are used for solids. Therefore, write the volume of object 1 in cm3.

3. Drag object 1 into the Beaker of Liquid. Does it sink or float? ________________________

Activity A: Float or sink?

Get the Gizmo ready:

· Drag object 1 back to the shelf.· Check that Liquid Density is set to 1.0 g/mL.

Question: How can you predict whether an object will float or sink?

1. Observe: Experiment with the different objects in the Gizmo. Try to determine what the floating objects have in common and what the sinking objects have in common.

2. Form hypothesis: Compare the floating objects, then do the same for the sinking objects.

A. What do the floating objects have in common? ______________________________

___________________________________________________________________

B. What do the sinking objects have in common? ______________________________

___________________________________________________________________

3. Collect data: Measure the mass and volume of objects 1 through 12, and record whether they float or sink in the table below. Leave the last column blank for now.

Object Mass (g) Volume (cm3) Float or sink?123456789

101112

(Activity A continued on next page)

Activity A (continued from previous page)

4. Analyze: Look carefully for patterns in your data.

A. Does mass alone determine whether an object will float or sink? ________________

Explain: ____________________________________________________________

B. Does volume alone determine whether an object will float or sink? ______________

Explain: ____________________________________________________________

C. Compare the mass and volume of each object. What is true of the mass and volume

of all the floating objects? ______________________________________________

D. What is true of the mass and volume of all the sinking objects? _________________

___________________________________________________________________

5. Calculate: The density of an object is its mass per unit of volume. Dense objects feel very heavy for their size, while objects with low density feel very light for their size.

To calculate an object’s density, divide its mass by its volume. If mass is measured in grams and volume in cubic centimeters, the unit of density is grams per cubic centimeter (g/cm3).

Calculate the density of each object, and record the answers in the last column of your data table. Label this column “Density (g/cm3).”

6. Analyze: Compare the density of each object to the density of the liquid, 1.0 g/mL. This is the density of water.

A. What do you notice about the density of the floating objects? ___________________

___________________________________________________________________

B. What do you notice about the density of the sinking objects? ___________________

___________________________________________________________________

7. Draw conclusions: If you know the mass and volume of an object, how can you predict whether it will float or sink in water?

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Activity B: Liquid density

Get the Gizmo ready:

· Drag all the objects back onto the shelf.· Check that the Liquid Density is still 1.0 g/mL.

Question: How does liquid density affect whether objects float or sink?

1. Observe: Place object 1 into the Beaker of Liquid. Slowly move the Liquid Density slider

back and forth. What do you notice? __________________________________________

________________________________________________________________________

2. Form a hypothesis: Buoyancy is the tendency to float. How do you think the liquid density

affects the buoyancy of objects placed in the liquid? _______________________________

_________________________________________________________________________

3. Predict: In the table below, write the density of each object. Then predict whether the object will float or sink in each of the fluids. Write “Float” or “Sink” in each empty box of the table.

Object Object densityLiquid densityLiquid densityLiquid density

Object Object density0.5 g/mL 1.0 g/mL 2.0 g/mL

12345

4. Test: Test your predictions using the Gizmo. Place a checkmark (\/) next to each correct prediction, and an “X” next to each incorrect prediction.

5. Draw conclusions: What is the relationship between the object density, the liquid density,

and the tendency of the object to float? __________________________________________

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Extension: King Hieron’s crown

Get the Gizmo ready:

· Drag all the objects back onto the shelf.· Set the Liquid Density to 1.0 g/mL.

Introduction: In the third century B.C., King Hieron of Syracuse asked the famous mathematician Archimedes to determine if his crown was made of pure gold. This was a puzzling problem for Archimedes—he knew how to measure the weight of the crown, but how could he measure the volume?

Archimedes solved the problem when he got into his bath and noticed the water spilling over the sides of the tub. He realized that the volume of the displaced water must be equal to the volume of the object placed into the water. Archimedes was so excited by his discovery that he jumped out of the bath and ran through the streets shouting “Eureka!”

Question: How can you tell if a crown is made of solid gold?

1. Think about it: Gold is one of the densest substances known, with a density of 19.3 g/cm3. If the gold in the crown was mixed with a less-valuable metal like bronze or copper, how would that affect its density?

_________________________________________________________________________

_________________________________________________________________________

2. Observe: Drag each of the crowns into the liquid. Based on what you see, which crown do you think is densest? Explain why you think so.

_________________________________________________________________________

_________________________________________________________________________

3. Measure: Find the mass, volume, and density of each of the three crowns.

Crown Mass (g) Volume (cm3) Density (g/cm3)ABC

4. Draw conclusions: Which of the three crowns was made of gold? _____________________

Explain: __________________________________________________________________

_________________________________________________________________________

Experiment - Measuring the density of liquidsClass practicalA simple method for comparing the density of liquids.

Apparatus and materials100 mL or 250 mL measuring cylinder, clean and dry

Kitchen balance or triple balance

Water, vegetable or olive oil, ketchup, vinegar

Any other liquids that are safe to handle (OPTIONAL)

Health & Safety

Take care with any spillages, particularly with the oil, which can create a slip hazard.

Procedure

a Take the measuring cylinder and measure its mass, in grams, as accurately as

possible.

b Take the measuring cylinder off the balance and add the water carefully, carefully

pouring until the level is as close to the 10 ml mark as possible. Put the measuring

cylinder back on the balance. Measure and record the new mass (cylinder plus water),

in grams.

c Repeat the procedure, adding 10 ml at a time as accurately as possible and recording

the volume and total mass, until the measuring cylinder is full. Then, for each volume

calculate the mass of the liquid alone.

NOTE: If a 250 ml measuring cylinder is being used you may wish to use 20 ml or 25 ml

intervals.

d Repeat steps a to c for the oil (and any other liquids being tested).

e Draw a graph of mass of liquid (y-axis) against volume (x-axis). Try to scale the graph

so that you can plot all your data sets on a single graph.

f For each set of data try and draw a straight ‘best fit’ line passing through the origin.

Calculate the density of each liquid from the slope of its graph line or divide the mass

(g) of the liquid (without the mass of the container) by the number of mL (each mL =

1cm3).

Teaching notes

1 Density =mass/volume so the units are g/cm3, or m3 and kg/m3. Either sets of units

are generally acceptable, but all length measurements must use the same unit.

Remember also that 1 ml =1 cm3.

2 mass = volume x densityDensity of liquids usually is expressed in units of g/ml. If you know the density of a liquid and the volume of the liquid, you can calculate its mass. Similarly, if you know the mass and volume of a liquid, you can calculate its density.Example Problem:Calculate the mass of 30.0 ml of methanol, given the density of methanol is 0.790 g/mlmass = volume x densitymass = 30 ml x 0.790 g/mlmass = 23.7 g3 The density of water is measured before the oil because water can be easily and

quickly rinsed out of the measuring cylinder and oil cannot. When adding the oil to the

measuring cylinder, instruct students to try and avoid pouring it down the side otherwise

it will form a coating on the sides which will increase the mass without raising the level

from which the volume is read, so dry the measuring cylinder before weighing.

4 If there are limitations to the number of balances available then it is still possible to

carry this out with students sharing a balance, although care needs to be taken that

there are no spillages. If students are not familiar with the meniscus that is formed,

show them how to take volume readings correctly.

5 How Science Works extension: If asked to find the density of a liquid, students may

take only a single set of readings. The ease with which water and other liquids can be

poured allows the refinement of this method to collect multiple results and use a

graphical method to minimize the effect of any systematic error in the measurements.

6 Finding densities of liquids and their behaviour is important to food scientists. You

could measure the density of vinegar, make and measure the density of a vinaigrette,

and then predicting which of these will sit on top when they are poured into a single

container.

Playing with Pascal

Curriculum connectionsGrade 8 Science, Cluster 3: Fluids

· 8-3-01 – Use appropriate vocabulary related to their investigations of fluids.

· 8-3-09 – Recognize that pressure is the relationship between force and area, and describe situations in which pressure can be increased or decreased by altering surface area.

· 8-3-11 – Compare the relative compressibility of water and air, and relate this property to their ability to transmit force in hydraulic and pneumatic systems.

· 8-3-13 – Compare hydraulic and pneumatic systems, and identify advantages and disadvantages of each.

· Note: This investigation will serve as an excellent precursor to 8-3-14 – Use the design process to construct a prototype that uses a pneumatic or hydraulic system to perform a given task.

Materials required· ring stand and test tube clamps· syringes of various sizes (for example, 1 cc, 3 cc, 5 cc, 10 cc) – any

‘piston-like’ objects will do, but syringes are conducive to quantitative measurement for the subsequent investigation due to their graduated markings

· vinyl tubing (1/4” diameter)· fluids – water, oil, alcohol, etc.· glycerine, petroleum jelly (to improve the seal in the syringes and to ease

plunger movement (lubrication))· masses – 100 g and 200 g (or objects representing similar masses)

Instructional sequence· Prior to class – Set up the demonstration as follows: Clamp one syringe (5 cc)

to each test tube clamp and affix these to the ring stand. Be sure to use syringes of the same size (e.g. 5 cc and 5 cc). The plunger end of both syringes should point upward. Connect the two syringes with a length of plastic tubing (approximately 15 cm). Fill this system with water.

· When your class is ready, have the students gather around the demonstration apparatus. Ask them to identify what they are seeing (syringes, tubing, water).

· Begin with the plunger of one syringe at the top (e.g. at the 5 cc mark) and the other at the bottom (e.g. at the 0 cc mark). With your thumb, press down on the syringe with the plunger that is out. Students will observe that the plunger in the second syringe will move upward. Ask them to consider why this is so, but do not provide them with an explanation.

· Place the smaller (e.g. 100 g) mass on top of the plunger of one syringe and the larger (e.g. 200 g) mass on the plunger of the other syringe. (Depending on the sizes of your masses you may need to use some sort of a platform to balance the mass on top of the plunger. Boxboard or cardboard will usually suffice.)

· Students will observe that the plunger with the heavier mass will go down. Explain that the larger mass produces more downward force than does the smaller mass and therefore goes down, causing the smaller mass to rise. Do not provide any more explanation than that yet.

· Have the students predict what would happen if you instead used syringes of different sizes.

· Repeat the demonstration with syringes of different sizes (for example, 3 cc and 10 cc), placing the larger mass on the larger syringe (this is key).

· Students will observe that this time, the larger mass will be lifted. They will likely be surprised by this. (Note: The larger the difference in syringe sizes, the more dramatic your results.)

· Ask the students to suggest possible explanations to this discrepant observation. Why is the smaller mass able to lift the larger mass?

· Carefully and clearly explain the science behind these observations before guiding the students into the investigation.

· Optional means of increasing student engagement: involve student volunteers to assist with the placement of the masses, changing of the syringes, etc.

Explanation of the science· In order for students to fully grasp the concepts discussed, it is crucial that

they clearly understand the particle nature of matter.· Begin with a role play in which students (volunteers might increase

engagement) act as water particles. Using masking tape, outline an area on the floor which will act as a container for the water.

· Place the students inside, ensuring that they are tightly packed. Explain that, in a liquid, the molecules are very close together.

· Next, use a large piece of cardboard (for example) and “push” on the water particles from one side of your container. This simulates a force on plunger of the syringe (i.e. your thumb or a mass) causing it to go down. The students should understand that they will not be able to get any closer together because the particles in a liquid are quite close together. (Be sure to use the phrase “The water cannot be compressed”.) As a result, they will

simply “press harder” on the sides of the container. Explain that this is results in an increase in pressure inside the container.

· Use a second large piece of cardboard to act as another plunger on the opposite side of the container. You may wish to use student volunteers to hold it in place. Have the students consider what would happen to this second plunger when the first plunger (cardboard) is pressed toward the inside of the container. Demonstrate this using the student water particles. The students should realize that the water, when pressed by the first plunger (cardboard) will then press on all sides of the container, including the second plunger. Thus, the second plunger will be pressed outward. Point out that the water is transmitting the force from the first plunger to the second. Emphasize that it can do so because the particles are so tightly packed. Otherwise, the force from pushing the first plunger inward would simply push the water particles closer together.

· You may wish to liken this to hitting a solid metal bar on the ground with a hammer. The force with which you strike the end of the bar will be transmitted through the bar and will “come out” the other side, driving the metal bar into the ground. The particles in the bar cannot be packed any more tightly, so they will transmit the force.

· Your role play should look something like this:

· You may wish to follow this with a diagram on the board or overhead projector with a repeat explanation. Your drawing of the pressure being exerted uniformly by water particles in a closed container might look something like this:

Continue the explanation as follows:· When you push down on the plunger (a force), you create a certain amount

of pressure inside the container (syringe). Tell the students that the amount of pressure inside the container (syringe) depends on the amount of force applied to the plunger (how hard it is pushed) and the surface area of the plunger (cardboard in the role play).

· Ensure that they understand that, according to Pascal’s law, the pressure exerted by the fluid will be the same in all parts of the container. In other

words, any force applied to a fluid is transmitted in all directions throughout the fluid, even if the fluid is in two different containers (syringes) connected by tubing. Emphasize that the shape and size of the second container will not affect the pressure.

· In this demonstration, the pressure will be the same in all parts of the system – the first syringe, the plastic tubing and the second syringe, regardless of its size (i.e. even if it is bigger than the first syringe). Students may not understand that the pressure will not decrease in a larger syringe – they may believe that the pressure will “spread out.” Do not proceed with your explanation until students understand the uniformity of the pressure. A drawing may assist in their understanding:

· The pressure in the second syringe will create a force on the second plunger, pushing it outward.

· The amount of force produced by this second plunger will depend on the pressure inside the syringe and the surface area of the plunger. If the two syringes are identical, then the force produced by the second plunger will be the same as that exerted on the first plunger.

· At the same time, the bigger the syringe, the bigger the plunger surface area and the more force it will produce. This is why, in the second part of the demonstration using syringes of two different sizes, the smaller mass was able to “lift” the larger mass.

· Students should clearly understand that using one small syringe (as input) and one large syringe (as output) is a good way of increasing force.

· When you have finished your explanation, you can tell students that in mechanics, the use of fluid (water) power in this way is called hydraulics. At this time, you may also wish to introduce the term pneumatics.

Safety concerns· Be sure to remove the needles from the syringes prior to the demonstration

and investigation.· Remind students that liquids used in the laboratory are not to be consumed.

ReferencesHowStuffWorks, Inc. How Hydraulic Machines Work. Accessed November 13, 2005, from http://science.howstuffworks.com/hydraulic1.htm.

Integrated Publishing. Engine Mechanics. Accessed November 8, 2005, from http://www.tpub.com/content/engine/14105/css/14105_22.htm.

Juniata College Physics Department. Mechanics: Fluids. Accessed November 12, 2005, from http://public.juniata.edu/physicsdemos/fluid-mechanics.htm#hydraulic%20press.

Playing with PascalDoing your own investigation

IntroductionIn our demonstration, you observed two syringes filled with water and connected by vinyl tubing. You saw that when we used a small syringe and a big syringe, a large mass could be lifted by a smaller mass using hydraulics. When we pressed down on the first plunger, a force was created inside the first syringe, the tubing and the second syringe. According to Pascal’s law, a pressure exerted by a fluid in a closed container is the same everywhere in that container. Because the water particles are so close together already, we say that the water cannot be compressed. So, the force we apply on the water with the first plunger is transmitted through the first syringe, through the tubing, into the second syringe, and onto the second plunger. Because the amount of force on the second plunger depends on the pressure on it and the size (surface area) of the plunger, the force created by the second plunger (the bigger one) was bigger than the force we “put into” our system.

In this activity, you are going to use what you have just learned to design and carry out an investigation. You will plan it, perform it and analyze your results.

Your questionUse the diagram below to help you come up with a question about this activity you want to investigate. For each part of the demonstration you saw, think of what you could change about it and if that change might affect how the system works. For example, consider how we could change the fluid in our syringes. Instead of water, we could use air, oil, or some other fluid.

Now think of 4 questions you might like to investigate. Sometimes it is helpful to start with “What if I…?”For example: (a) What if I used air instead of water? Would that

create more force? (b) Would using a longer piece of vinyl tubing make it

work better?(c) What would happen if I used a big syringe (to act as

the “in”) and a small one (to act as the “out”)?

List your questions here:1.2.3.4.

Circle the question you would like to investigate today.

Your planUse the framework below to help you plan the investigative procedure you will use to answer your question. Remember you are designing a fair test. You want to be sure that what you have changed is affecting what you will measure and that nothing else is affecting your investigation.

What will you change?·

How will you change it?·

What will you keep the same?···

What will you measure?·

How will you measure it?·

Using the information you have just given, write out a method of fairly testing your question. In your plan, remember to do many trials to help ensure that your results are accurate. Start by listing what materials you need, then write out your plan as a series of steps (1., 2., 3., etc.). Including diagrams might help. (You can use the back of this page if you need.)

Your predictionsWhat do you think the answer to your chosen question will be? Explain why. Think back to how we explained the demonstration.

Your resultsConstruct a data table to display the results of your investigation here. Be sure to include the results from all trials. (You may use the back of this page if you need.)

Analysis of your results· Describe your observations. What did you see when you

performed your investigation?

· Were your results as you had predicted? If not, how were they different?

· Explain why you saw what you did. Include observations you expected and those you did not expect. Again, for help, think back to how we explained our demonstration.

· Was this a fair test? Did you get the same results every time you repeated the test? If not, why not?

Summary and Conclusions· Based on your investigation, make a conclusion about what

you have observed. For example, “Using hot water instead of

cold water in our hydraulics system did not produce more force.”

Boyle’s /Charles’ Law Calculations

Boyle’s Law can be used to compare changing conditions for a gas. We use and to stand for the initial pressure and initial volume of a gas. After a change has been made, and stand for the final pressure and volume. The mathematical relationship of Boyle’s Law becomes:

This equation can be used to calculate any one of the four quantities if the other three are known. Pressure can be measured in kPa (kiloPascals) or atm (atmospheric pressure). Either are possible in the formula, but the same units must be used in one equation. ie. If you start with kPa, your answer will be in kPa.

1. If the pressure is 0.9 kPa. and the volume is 4.0L , then the pressure changes to 0.20 kPa. What is the new volume?

2. If the pressure is 1.90 atm. and the volume is 27L, then the volume changes to 03.0 L. What is the new pressure?

3. If the pressure is 1.9 kPa. and the volume is 8.0L , then the pressure changes to 0.780 kPa. What is the new volume?

4. If the pressure is 0.50 atm. and the volume is 27L, then the volume changes to 53.0 L. What is the new pressure?

5. What is the formula for Charles’ law?

Note: the Temperature needs to be in degrees Kelvin (based on 0 degrees being absolute zero where molecules cease to move or vibrate). To do that you need to convert oKelvin = oCelsius + 273.15 ie. 15oC = 288.15oKFor the following problems, assume the pressure is constant because it’s in a container that won’t expand.

6. If the volume is 0.50 atm. and the temp. is 27C°, then the temp. changes to 095.0 C°. What is the new volume? (remember to convert to Kelvin)

7. If the volume is 0.90 kPa. and the temp. is 45C°, then the temp. changes to 0395.0 C°. What is the new volume?

8. If the volume is 0.90 L and the temp. is 45C°, then the volume changes to 2.00L. What is the new temp.?

9. What is the beginning temperature if the volume is 4.5L . The final volume is 2.3L and the final temp. is 18.87 C°?