What is air?

Recall syringe

• What happened when you mixed citric acid and sodium bicarbonate?

• It produced a gas

• What could that gas be?

• What could the gas be made of?

List gases you have heard of

• Make a list with group LM p 24 #1

Define gas

• In your own words LM p 24 #2

• Gas:….

Gas

• Physics . a substance possessing perfect molecular mobility and the property of indefinite expansion, as opposed to a solid or liquid.

• A state of matter with no definite shape or volume

What elements could be in the gas that forms when sodium bicarbonate and citric acid

react? LM p 24 #3• Carbon ( C )

• Hydrogen (H2)

• Oxygen (O2)

• Sodium (Na)

Possible gases

• H2 or hydrogen

• O2 or oxygen

• CO2 or carbon dioxide

• H2O or water vapor

What gases could be produced when you sodium bicarbonate and citric acid

react?

• LM page 24 #4

Gas produced

• When you add sodium bicarbonate and citric acid the gas produced is carbon dioxide

• NaHCO3 + C6H8O7 CO2 + H2O+Na3C6H5O7

What is air?

• In the atmosphere

• We breath it

• Mixture of gases (learned in 7th grade)

• Is matter

How can we prove air is matter?

• How can we find out if the air in the ball has mass?

• Demo with ball

• What caused the mass of the ball system to change?

• Does air take up space in the ball?

• How do you know?

Is air matter?

We know because the ball weighed less before we added air then it did after we added air.

• The air caused the ball to increase in mass so the air must have mass

• The ball is more full, or firmer, so the air takes up space

• If air has mass and takes up space then it is matter

Let’s explore

• Using a syringe system

• Syringe, tubing, binder clip

• May work with air or without air

Explore

• Rules

• Do not use the syringe systems to annoy anyone

• You can use the clip

• Work with partners

To remove the tube

• Use fork and pry gently

• DO NOT POKE OTHERS WITH FORK

Try this

• Put the tube on the syringe

• Pull out the plunger a little

• Bend the tube

• Put on the clip

• Take turns practice pushing and pulling the plunger

• Make a note about your observations

Now

• Connect 2 syringes with the tube

• Push and pull and see what happens

• Note observations

Transparency 6

• Answer questions in notebook LMp 25

Vocabulary

• Air is a mixture of gases.• Air is matter. It has mass and takes up space.• Compressed air: air that is forced into a

smaller space• Expanded air: to occupy more space, when

the force holding air in a smaller space is removed the matter occupies more space.

Air

• Composed of tiny particles too small to see

• Particles are constantly moving and have space between them

• They bounce off of one another and the sides of their container all the time

Imagine you can see the particles inside the syringe

• Explain what you think is happening to the air particles as you compress and expand the air inside the syringe.

Plastic bubbles

• I have cut bubbles from a sheet.

• DO NOT POP THEM!

• Put the bubble into the syringe

• Insert the plunger half way

• Clamp the tubing to make a closed system

Plastic bubble continued

• Think about what is happening to the syringe, the air inside the syringe and the air bubble as you apply force.

• Push and pull and observe• Make notes of your observations• Talk to your partners.• Come up with an explanation for what you

observe that includes what is happening to the air particles

Discussion

• What is inside the syringe?

• What is in the bubble?

• What happens to the air in the syringe when you push down on the plunger?

• What happens to the bubble when you push on the plunger?

Discussion continued

• Why does the bubble shrivel?

• What happens to the bubble when you pull up on the plunger?

Air as particles

• Lab Manual page 25

• Work as a group and write short precise answers to the seven questions

• 7 minutes

LM page 25

• What is the air in the syringe and the air in the bubble made of?

• *Air particles

What happens to the air particles in the syringe when

you push on the plunger?

• *The air particles are pushed closer together

What happens to the air particles in the bubble when you pull up on the plunger?

• *They get farther apart

Are there more air particles in the bubble when it is

compressed or when it is expanded?

• *Always the same number. The bubble is sealed. No particles can go in or out.

When you push on the plunger, are the air particles closer together in the syringe

or in the bubble?

• *The average distance between particles is the same in the syringe and in the bubble

What is between air particles?

• Nothing- only space or distance, but no matter.

What happens to air particles when a volume of air is

compressed?

• *Particles are closer together.

When a volume of air expands?

• *Particles are farther apart.

Air in a Syringe

• Lab Manual pages 26-27• Read along silently as I read aloud• 10 minutes to complete page 26-27 and

complete drawings • Turn in• Homework/Class work: Read “Particles” page

14-15 Resource Book• Complete questions LM page 29

Key Points• Air is matter. It has

mass and takes up space.

• Compressed air: air that is forced into a smaller space

• Expands: to occupy more space, when the force holding air in a smaller space is removed the matter occupies more space.

• There is nothing between particles of gas-only space

• During compression and expansion the number and size of particles in a sample of gas do not change. Only the space between the particles.

particle

• Smallest piece of any substance that is still that substance

Diagram of a water particle