Transformation of Water (H2O)

The measure of the average energy of motion of the particles substance

TEMPERATURE

http://www.media.pearson.com.au/schools/cw/au_sch_whalley_sf1_1/int/2_slg.htmlAnimation- particles and movement

The measure of the average energy of motion of the particles in a substance

TEMPERATURE

Image Source: http://www.adelaidehydronicheating.com.au/solarhotwater.html

States or Phases of Water

The Phase or State of matter is a physical characteristic. describes a PHYSICAL state of matter. As matter changes from one state or phase of matter to another, a physical change occurs.

If energy is added (like increasing the temperature or increasing pressure) or if energy is taken away (like freezing something or decreasing pressure) those are physical changes.

http://www.media.pearson.com.au/schools/cw/au_sch_whalley_sf1_1/int/2_slg.htmlAnimation- particles and sublimation

Changes in state are physical changes

Image source: http://itl.chem.ufl.edu/2041_u99/lectures/lec_f.html

Every substance contains energy from the movement of its particles, called thermal energy. The higher the temperature of a substance, the greater its thermal energy.

Requires energy from environment

Releases energy to environment

Tempe

rature

(deg

rees C

elsius)

Time (minutes)

0

100

Time- Temperature Graph for Water

As the temp approaches melting point temperature, the KE of the water molecules increases loosening the bonds between water molecules.

As the ice begins to melt, additional heat energy does not raise the temperature of the water, but loosens the bonds changing ice to water. i.e. phase change – melting.

Once the water is in a liquid phase, increasing the amount of heat input raises the temp of the liquid water.

As the temp approaches boiling point, the KE of the molecules is sufficient to allow the separation of molecules into the gas phase.

As the liquid begins to boil. Additional input of heat energy does not raise the temperature of the water, rather it is used to break water bonds. i.e. phase change.

Once the water is in the gas phase, additional heat input raises the temperature of the water vapor Note: greater energy is needed to vaporize water than to melt it. WHY?

Phase Change- Meltingenergy from stove = energy required for phase change

NO temperature change

Phase Change- Vaporization

Energy from hot plate causes

increased KE and increased Temperature

Energy from hot plate causes

increased KE and increased Temperature

Two states of Matter

Two states of Matter

One state of Matter

Energy from hot plate = energy required for phase change

No temperature change

Phase Diagram of Water

Energy used to loosen bonds; No change in temp.

Energy used to break the bonds; No change in temp.

Energy causes particles to vibrate

Lab Demo. A Soluble Problem

Summary: Define the terms soluble and insoluble.

Soluble Insoluble

DISSOLVED

Lab 1: SOLUBILITYWhat are solutes, a solvents and a solutions? Does stirring help solutes to dissolve?

METHOD 1. Place one of the candy pieces in your mouth without chewing or moving your tongue around. 2. Record the time that it takes for this candy piece to dissolve. 3. Place a second candy piece in your mouth, this time moving

your tongue, but not chewing. 4. Record the time it takes to dissolve this candy piece. 5. Place the third piece of candy in your mouth and chew it. 6. Record the time to dissolve this third piece of candy.

Time (sec)

Dissolving

Mixing

Chewing

2. Copy and complete the following sentences using the words below:

Solution solvent solute salivadissolves exposed saliva

The candy dissolves in the ……………………..in your mouth to form a liquid ………………………….. Solutions contain two parts, a ………………….. and a ……………………………….

The solvent is …………………….. and the solute is the candy. The solute……………………….. by spreading out evenly throughout the solvent. The candy can quickly dissolve when it is ……………… to chewing and stirred by moving it around with the tongue.

Lab 2: ANOTHER STIRRING PROBLEM

How does stirring help solutes to dissolve?

METHOD 1. Measure 100mL water and place this in a beaker. Prepare two (2) setups.2. In one beaker, add 1 spoonful of sugar.3. Record the time it takes to dissolve the sugar. 4. In the other beaker, add 1 spoonful of sugar. 5. Stir until the sugar dissolves. 6. Record the time it takes to dissolve the sugar.

Time (sec)

No Stirring

Stirring

Explain your results: Answer the aim.

It All Depends on the TemperatureAim: Why do many substances form solutions more easily in hot water than cold water?

Materials: 2 small beakers hot water food coloring

METHOD

1.Fill one beaker with cold water.2. Fill the other beakers with hot water.3.Wait one minute for the water to calm.4.Add one drop of food coloring to each.5.Record your observations over the next 5 minutes. Note: DO NOT MOVE THE BEAKERS

GUIDE QUESTIONS:

1.How does the temperature seem to affect the rate of mixing?

2.How is the warm solution different from the cold one?

3.Describe what is happening in terms of particle movement.

4.Draw a dot sketch of each solution. Use more dots to show areas where there is a high concentration of food coloring and fewer dots for low concentration.

Mixtures and Solutions

Molecules are small groups (2 or more atoms) of atoms.

Compounds are pure substances made of 2 or more elements chemically joined together (bonds).

Magnesium Atoms

Oxygen Atoms

Molecules of magnesium oxide

Summary

element element compound

atom atom molecule

Which are molecules and which are compounds?

A MIXTURE is a material made up of at least two substances which may be elements or compounds that are NOT chemically bonded .

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mixtures.html

Image Source: http://www.google.com.ph/imglanding?q=mixtures+and+compounds&hl=tl&sa=X&biw=1020&bih=567&tbs=isch:1&prmd=ivns&tbnid=eet6vXOJz3eqM:&imgrefurl=http://

www.quantumtheatre.co.uk/BDks2web.html&imgurl=http://www.quantumtheatre.co.uk/BDks2web_files/image006.jpg&ei=QT1jTZTfC4ukugOH0d28AQ&zoom=1&w=604&h=292&iact=rc&oei=QT1jTZTfC4ukugOH0d28AQ&page=1&tbnh=90&tbnw=1

87&start=0&ndsp=14&ved=1t:429,r:4,s:0

Properties of Mixtures

• The composition of a mixture is variable. • Each of its components retains its

characteristic properties. • No chemical reaction is involved• Its components are easily separated (e.g.

filtration, evaporation).

A mixture in which one substance (solute) is dissolved in another (solvent) and the

molecules are evenly distributed.

SOLUTION

Image source: http://www.ssc.education.ed.ac.uk

Salt Solution

http://intro.chem.okstate.edu/ChemSource/Solutions/image3QT.JPG

Image source:

Post-Lab: Physical Changes

Activity 1. Evaporation of Liquids

Describe what happens to the particles during this process. Explain why this happens.

Evaporation happens when atoms or

molecules escape from the liquid and turn into a vapor.

What factors can affect the rate of evaporation?

The energy you can measure with a thermometer is an average of all the molecules in the system.

There are always a few molecules with a lot of energy and some with barely any energy at all.

Alcohol Water Oil

NATURE OF THE SUBSTANCE

Some liquids have __________ forces that hold particles together allowing some particles to escape.

What factors can affect the rate of evaporation?

The molecules with a lot of energy are able to build up enough power to become a gas. Once they reach that energy level, they can leave the liquid and thus, it has evaporated.

Force of air pressing

down

Image source: http://www.vtaide.com/png/evaporation.htm

Factors affecting the rate of evaporation

Applying Understanding: Real-life situations

Why do you spread out your wet clothes to dry?

Why do you feel cool when you stand next to a fan?

Why do you feel cold when you immediately step out of the shower?

Why is it important to “ rehydrate? Relate “sweating” to evaporation and our body’s ability to regulate temperature.

FREEZING POINT

Change in phase from liquid to solid

Why?When energy is taken

out from a liquid, particles slow down

until forces of attraction cause them to fuse and

form a solid.

Image source: http://www.factfrenzy.com/what-is-the-freezing-point-of-water/

Particles of a liquid

Particles slow down

Particles fuse

Why is salt added to a snow-covered driveway?

Salt dissolves in water pretty fast. When you sprinkle salt on ice, the salt lowers the freezing point of the water, keeping it from re-freezing as easily and helping to melt the rest of the ice. This is called lowering the freezing point.

http://www.stevespanglerscience.com/experiment/how-does-salt-melt-ice

When you add salt to water, the salt (called sodium chloride, NaCl) dissolves into particles (actually called ions of sodium and chloride). The freezing point of water becomes lower as more particles are added until the point where the salt stops dissolving. On a driveway or street, sodium chloride can melt ice only down to about (-9°C).

http://www.stevespanglerscience.com/experiment/how-does-salt-melt-ice

BOILING POINT

Evaporation takes place at surface

of liquids

Boiling takes place beneath

surface of liquid

Animated GIF "Boiling" - Courtesy of General Chemistry Help - Purdue University

Image source: http://www.elmhurst.edu/~chm/vchembook/163boilingpt.html

This animation shows how water molecules are able to break the forces of attraction .

This is what is happening inside the gas bubble as it is rising to the surface to break and release the water gas molecules.

In a liquid, molecules are packed closely together. As a liquid is heated, the temperature is increased. As the temperature increases, the kinetic energy increases which causes increasing motion. Eventually molecules break free of liquid and become a gas. At the temperature of the boiling point, the liquid turns into a gas.

Activity 2. Boiling Point of Liquids

How does a coolant help prevent overheating?

Car Engine

Increases a liquid’s boiling point

How can you make water boil below

100° C?

http://www.youtube.com/watch?v=9q5gEZGoBnk Vacuum Chamber

How does pressure affect the boiling point?

Physics in the Kitchen

Physics in the Kitchen

How does a

pressure cooker work?

Physics in the Kitchen

•It is the high temperature that cooks the food.

• Pressure affects boiling. Increased pressure raises the BP.

• Pressure cookers increase the pressure inside and prevent boiling.

• The increased temperature cooks food faster.

Never boil water in a MicrowaveSource: http://www.stevespangler.com/teaching-moments/warning-water-can-explode-in-the-microwave/

A man decided to have a cup of instant coffee, so he heated a cup of water in the microwave. When the timer went off, he removed the cup from the microwave and noticed that the water had not boiled.

Just then, the water literally “blew up” in his face. His whole face was blistered with first and second degree burns, which left some permanent scaring and damage to his left eye.

While at the hospital, the doctor attending him stated that his is a fairly common occurrence. Water (alone) should never be heated in a microwave oven.

Never boil water in a MicrowaveSource: http://www.stevespangler.com/teaching-moments/warning-water-can-explode-in-the-microwave/

Why? This phenomenon is known as superheating. It can occur anytime water is heated - especially if the cup or bowl is new. What happens is that the water heats faster than the vapor bubbles can form. If the cup is very new, then it is unlikely to have small surface scratches in it that provide a place for the bubbles to form (called nucleation sites).

Without bubbles, the water cannot release the heat that has built up, the liquid does not boil, and it continues to heat up past its boiling point. If the water is bumped or jarred, it's enough of a shock to cause the bubbles to rapidly form and the result is an exploding liquid that is scalding hot. One solution is to place a wooden stir stick or something non-metallic in the water to help spread the energy as it is heating in the microwave.

Sublimation and Deposition

Solid to gaseous form, or vapor

Deposition(Formation of

Frost)

Frost-Free Freezers

MELTING POINTS

http://www.sciencekids.co.nz/gamesactivities/meltingpoints.html

Melting Points

temperature at which it changes from a solid to a liquid.

The melting point allows chemists/industrial engineers to create alloys that would be far much stronger than the original materials that are being melted.

Steel is an alloy. Most of the stuff that we use - e.g., tennis rackets, bedframes - are alloys - and melting points allow for the creation of these alloys.

How Do Satellites And Launch Vehicle Stages "Breakup" During Reentry From Orbit?The breakup of reentering objects typically occurs around an altitude of 45 to 50 miles (70 - 80 km) above the Earth's surface. Low melting point materials melt first, exposing other objects to the extreme heat and forces of reentry. As pieces melt or break away, the heating and deceleration loads increase, further breaking the object apart and creating multiple pieces of debris. The debris forms meteor-like streaks in the sky. Some of the debris survives and impacts the Earth's surface along a footprint that can be hundreds of miles long.

What Happens To An Object During Reentry?

Crewed space vehicles have protective heat shields, allowing them to survive reentry and land on the ground. Most objects however, such as satellites and launch vehicle stages, lack protective shielding. These objects burn and break apart during reentry.

Source: http://www.tvaero.com/reentry.shtml

Summary: States or Phases of Water

The Phase or State of matter is a physical characteristic. It describes a PHYSICAL state of matter. As matter changes from one state or phase of matter to another, a physical change occurs.

If energy is added (like increasing the temperature or increasing pressure) or if

energy is taken away (like freezing something or decreasing pressure) those are

physical changes.

http://www.media.pearson.com.au/schools/cw/au_sch_whalley_sf1_1/int/2_slg.htmlAnimation- particles and sublimation

Image source: http://cse.ssl.berkeley.edu/artemis/mission_sunearth_closeup1.html

https://gcps.desire2learn.com/

Matter changes whenever energy is added or taken away.

Energy is added: Solid Liquid Gas

Energy is removed: Gas Liquid Solid

States of Matter Phase Change Energy

Movement During Phase

Change Energy

IN or Out

Temperature Change During Phase Change

Solid to liquid Melting Energy into solid None

Liquid to solid Freezing Energy out of liquid

None

Liquid to gas Vaporization, which includes

boiling and evaporation

Energy into liquid None

Gas to liquid Condensation Energy out of gas

None

Solid to gas Sublimation Energy into solid None

Why is melting (solid to liquid) and vaporization (liquid to gas) considered a cooling process?

To change from a solid to a liquid or a liquid to a gas requires an increase in the KE of the matter. This KE comes from the environment.

A loss of KE from the environment lowers the temp of the environment resulting in a cooling process.

Why is freezing (liquid to solid) and condensation (gas to liquid)

considered a heating process?

To change a gas to liquid or a liquid to solid requires a decrease in the KE of the matter. This decrease in KE results in a warming process.

Image source: chemistrytutorials.org