7th grade Science Core Test Yearly Review

You can do it!!!!

Random thoughts we have learned about:

• Inference –vs- fact.• An inference means we see something and begin to assume or decide

something about the “thing”. How it works, what it does, what it will do, etc.

• Example: Why does a cat lick it’s fur all the time?• We infer that they want to be clean.

• What fact is really behind the licking of the fur? It helps to regulate a cat’s body temperature also and is more vital than the cleaning.

If you are shown information in a picture, read what the question is and then look carefully at the picture. It may not be something you

had to learn but is simple observation.

• Example: Which picture would provide the better garden area and why?

• The first because it is more fertile and full of minerals to help plants to grow.

Bacteria and other organisms can slowly adapt to their surroundings.

• Why could these products be a problem?

• Some bacteria begin to adapt to the chemicals and they become too strong to be killed = super bugs. (Most adaptations happen over a long period of time).

The differences between the following:

• Microscope: to see very small things like bacteria. Cannot see atoms or viruses.*Telescope: To see into space-planets,etc.*Stethoscope: to listen to your heartand lungs—doctors and nurses use them.*Spectroscope: to see the full color spectrum.

Logical thinking processes:

• Say you were bitten by a dog. The authorities would want to know the characteristics of the dog so they could identify, catch and contain the dangerous dog. Would it make a difference in catching the correct dog and taking care of the problem? YES!!

If scientists change information what causes them to do this?

• As our technology becomes more advanced, it allows scientists to see details that may have not been visible until that technology advancement. It does not mean that the organism they have been studying has changed, the details simply were not visible at the time. Better technology can often mean better information that was simply not seen when the studies first began. Scientists will then add this newly discovered information to the existing bank of information. Science is continually discovering more information and they inform the public when new information has been discovered.

• Example: The atom which has and most likely will continually have new found information added to our knowledge bank.

• Dalton Bohr/Rutherford Thomson

Common Sense questions• There may be questions that ask you to make a judgment

decision based on a small bit of information that is given in a story or a lab setup. Remember that there will usually be two answers that are really way off and that leaves two for you to think about. You can do it! Remember to connect ideas and concepts to other ideas and concepts that would match and make sense.

Review on Atoms

• They are the smallest piece of any element. If you take gold and cut it in half and cut it half and cut it in half—etc, you would finally get to only a piece called the atom.

• Atoms are too small to see with our class microscopes. Electron microscopes must be used to see atoms.

• As our technology becomes better the scientists are able to see what they could not see before and then they add this information to our “bank” of information.

How many hydrogen atoms could fit on the head of a pin?

• 5 million, million could!

• Not on this idiot-----------------

• This type of pin-very small!

When I take atoms and combine them what do I have?

• Molecules! Like H2O, which is water.

• Or CO2 which is• carbon dioxide.

All atoms and matter are in constant motion

• Solids with a definite shape and volume but the atoms still vibrate.• Liquids that have a definite volume but not a definite shape. The atoms can roll around each

other.• Gases do not have a definite shape or volume because they will take up as much space as

possible and will take on the shape of their container—these atoms are moving the most and bouncing off the walls of their container. They are also crashing into each other. They move the fastest of all states of matter.

• Atoms are in constant motion!

• When heat is added to something it will cause the atoms in it to move faster.

• This can explain the expansion of materials when they are heated and the shrinking in size when they are cold. Think of bridges where they meet roads. They have attachments that allow shrinkage in the winter (cold causes shrinkage) and expansion in the summer (things swell when hot)

What is the one exception to this “cold get smaller and hot get bigger” rule?

• Water! This is the only substance that when it gets cold---like ice---it actually swells and becomes larger.

• Think of tires in the summer—if the air is heated the tire pressure may appear higher because the atoms are hot and moving faster. On the other hand, in the winter the tire may seem to lose tire pressure because it is cold and the atoms are moving very slow and not as far = a flat looking tire. Always use a tire gauge before simply adding air to your tires—you may be making a mistake!

Diffusion

• The movement of molecules from a higher concentration to an area of a lower concentration.

• Remember the room spray—I sprayed it all in the middle of the room (high concentration)—then the students on the edges of the room(lower concentration area) gradually could smell the scent as it diffused around the room.

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Another example

• You come home and the whole house smells yummy because your mom baked a razzleberry pie. Why can you smell it—you are not in the kitchen where the pie is?

–Diffusion!!!

Osmosis is the same as diffusion except it concerns the movement of water only.

• Think of your egg experiment—water moves into the areas where less water exists, (remember high to low concentration) therefore water went into the egg and the egg appears swollen. Because there was less water in the egg than outside the egg so water goes where there is less of it.

• In syrup the• egg lost water• to the syrup• and shrank. There• was less water in • the syrup so the • water left the egg• and went out into the• syrup. That’s why your• syrup was all watery.

What would happen to diffusion if there were more molecules to diffuse through?

• It would slow down the diffusion speed but the diffusion would still occur—it is a natural law of nature.

• Example-humid air –vs- dry air. With humidity there is water vapor in the air also. Therefore, the diffusion of a spray would diffuse from where you sprayed it; it would simply take a bit longer to diffuse throughout the whole room because it had to diffuse through all the molecules in the area.

Earth’s density layers

• Remember that the most dense substance will always go to the bottom in this case the center and then each next dense layer will follow. This is true with everything.

What if I put Earth materials (sand, rocks, silt, pebbles, leaves, etc.) into a jar with water and

shake it up—how will things end up?• By densities of• the material---• of course!!!! • The most dense• on the bottom • and working to• the lease dense• at the top.

What evidence do we have that the Earth has layers?

• Scientists have used core samples and even Earthquake wave data to confirm the findings that the Earth has a liquid core and a solid core. The waves of an Earthquake will go faster through a solid and slower through a liquid. This is a proven fact.

• If scientists discover more information, they will share it with the world and then we all know.

What causes something to float?

• If the “something” is less dense than the liquid it is put in, then it will float!

• If the “something” is more dense than the liquid it was put in---then it will sink!

Just what is density?• How much “stuff” is packed into the space.• Remember the wood blocks and the styrofoam

blocks that I put into water? They were one size but the wood sank and the styrofoam floated. The wood was more dense and it was more dense than the water so it sank to the bottom of the tank.

• Remember-how much stuff (molecules/atoms) are stuffed into

The formula for density is D = M/V• That is to say that density equal mass divided by volume.• Lets do a quick review:• What is volume? How much space something takes up.• How do we measure volume? If the object is irregular then we

use a graduated cylinder. Measure in an amount of water, (50 mL.) place the item into the cylinder of water, write down the new water line (75 mL.) and then subtract the numbers. The difference is the volume of the object we placed into the water. (25 cm3) Remember to use the correct notation for the measurement.

• If the object is regular we measure the height, width, and length and multiple it together.

Examples:

• You measure the water, note the water line, add the irregular object, note the water line again and subtract to find the volume of the object.

• Easy!!!

So—my mass is 120 g. and my volume is 60 cm3. What is the density?

•2 g/cm3 Yes!!

Try this problem---• Irregular object—what must I use to find the volume? • Graduated cylinder-yes!• If the water read 55 mL and now it reads 73 mL, what must I do next?• Subtract to find the volume– 18 mL-yes!!• The mass is 54 g. What do I do next?• Take mass divided by volume M/V and then I get the density (g/cm3)

• It is 3 g/cm3• Do not forget any of the proper

steps!!!!!!!!

What about a rock called “pumice”

• It has lots and lots of air bubbles and holes in it. It is a form of volcanic rock that actually floats in water because it has such a low density—of course due to the holes and air bubbles. It has a density of 0.2 g/cm3—less than water so it floats!

So---

• In class you learned about a wood that does not float (iron wood) it is extremely dense for a wood. (1.17-1.33 g/cm3).

• You also learned about a rock that has a very low density and it floats. (pumice).

This is completely off the wall but:• If a body of water like a stream or river is carrying sticks and logs and rocks

and boulders and pebbles along with the flow----as the flow becomes weaker what would likely fall to the bottom of the stream or river bed first?

• Yes---the heaviest objects or you could say the most dense ones. In this case the boulders, then rocks, then pebbles, etc. They would be deposited along the sides or bottoms of the river.

What about life?• All living things must meet certain requirements to qualify as

“living”• 1. They have a cellular organization.• 2. They contain similar chemicals.• 3. They use energy.• 4. They respond to their surroundings.• 5. They will grow and develop.• 6. They will reproduce.• You have a few exceptions like a mule but mankind messed

with genetics and that was the outcome—remember a mule cannot reproduce.

Life subjects

• Smallest unit of life is the cell.• In living things there is a pattern of how things

are made up.• Cells make up tissues. Tissues make up organs,

organs make up systems (circulatory, skeletal, digestive, etc) and all the systems work together to make up the organism so it functions correctly.

Plant cell parts

Eukaryotic cells

Difference between plant and animal cell.

• PlantAnimal Both_____• Cell wall no• Chloroplast no• Vacuole sometimesX• Nucleus yes X• Cell membrane yes X• Ribosomesyes X• Lysosomes yes X• Mitochondria yes X• ER yes X• Golgi body yes X• Cytoplasm yes X• Do you remember what the cytoplasm does? All the organelles are floating in this

jelly like substance inside the cells membrane.

What about a rock or a mineral—do they have cells?

• NO!! They are not a living thing—never were and so they do not have a cellular structure. They usually have a crystal structure or can be smaller rocks all crushed together into one big rock.

• A petrified rock is different. It is usually a once living organism that over time has had all the organic materials replaced with minerals and so it is hard and turned to stone.

Body systems review

• Nervous system-brain, spinal cord and all nerves-allows messages from the brain to tell your body what to do.

Integumentary system (skin)

• Your skin is your biggest organ and protects your whole body.

Skeletal system

• Allows your body to• have support and • structure.• Also allows movement• when working with• your muscles.

Muscular system

• Allows movement and strength and also form.

Respiratory system

• This one brings oxygen• into your body to reach • your lungs, blood, and• into your cells. Also • carries our the waste• of carbon dioxide.

Digestive system

• Allows you to eat and gain the nutritional benefits of the food. It is

• sent to your cells to• use an energy to• continue growth• and body processes.

Urinary system

• This system cleans the• liquid wastes from your • body and recycles the • good liquids.

Again---the size from small to large

• Cell

Cells then make up different tissues

Tissues make up different organs

• Like eyes, liver, heart, stomach, etc.

Organs go together to make up the systems:

• Respiratory, digestive, urinary, respiratory, etc.• Just like the ones we have shown you.

All the body systems make the whole organism—me, you, cats, dogs, etc.

Classification System

• Linnaeus came up with the first classification system.

• Classification is based on similarities.Whenever new information is found it is considered and sometimes

classifications are changed. There have been instances where new categories were made and also animals moved into a different classification (skunk)

All animals are built by nature to best suit their surroundings and how they live, hunt, play, and reproduce. Examples are wings on birds, waterproof feathers on water fowl, night vision for nocturnal animals like a cat and owl, big fins on fish along with smooth and streamlined bodies to swim quickly, long arms on monkeys to swing from tree to tree, etc.

Classification keys

Lets try a leaf– 1. Has needle-like leaves …………Pine– Has flat, broad leaves …………go to 2– 2. Has more than one leaf per stalk ………..Chestnut– Has only one leaf per stalk …………go to 3– 3. Has smooth edges ………….Dogwood– Has lobed, jagged edges ………….Acorn

–The answer is Acorn!!

Example of classification:

Remember

• The longer the animals are together, the more similarities they share.

• There are three domains—• Bacteria-these lack a nucleus and are also called

prokaryotes• Archaea-the odd ones that can live in extreme

areas.• Eukarya- with a nucleus and divided into four

kingdoms of protists, fungi, plants, or animals.

Genetic information• Information that makes you look like you and your friend look like she/he

does. The genetic traits were inherited from parents. • Your hair color and eye color and height were inherited from parents. If

you practice hard at kicking a football with your long legs you can acquire the ability to be a good athlete. Your environment can influence your genetics. Good food or bad food can have an effect on you just like exercise or no exercise can change your body form.

So—can a farmer or horse racer plan and breed the animals for certain traits?

• Yes-he can choose the animals with strong legs or big muscles, even height and use it to his advantage. After he mates the animals he can further the advantage with trainers and good food. This can be done with animals and plants to get better food.

Asexual –vs- sexual reproduction

• Asexual is without sex and so the male and female genetic traits are not combined. The cell or bacteria will usually divide and where there was one, now there is two. They are genetically identical.

So, do you think if I take a cutting off a plant and put it in a glass of water it will

grow?• Yes—this is a form of asexual reproduction.• The cuttings begin to form root tips like the

second picture and then full roots. The plant can then be taken and planted into soil

Sexual reproduction

• Male and female have the genetic traits combined for a 3rd new person who is not identical.

+ =

What traits would benefit animals?

• Strength to fight and/or run from predators

• Ability to camaflage to hide from predators

Well—that is all folks!!

• PHEW! We made it.

• Good Luck!!