Pressure in a Jar

• What do you think will happen to the water in the tube when I squeeze the jar?

• Record your predictions under Part 1 of page 45 of your lab book.

Day 40

Investigation 8 part 1Air Pressure Inquiry

Syringes and Pressure

• Remember the activity with the syringes and tubing

• Describe the investigation• The air was compressed

when the plunger was squeezed• The blue foam cube became

smaller because the air insideit was compressed

Air-Pressure Inquiry

• Plastic jar that is tightly closed• The inside glass is half filled

with water• A stopper with tubing is

pushed tightly into the glass bottle

Pressure in a Jar

• In your groups: Assemble a pressure indicator as instructed.

• Materials:-rubber stopper- clear plastic tube-Glass bottle- Plastic jar

Gently Squeeze the Jar…

• What happens to the water level in the tube?• Surprised?

• Water level in tube goes down!!• Explain why this happens!

Results

Air molecules are squeezed closer together

When you squeeze the plastic jar…

Water molecules can not be squeezed closer together - it’s

a liquid

Results

When you squeeze the plastic jar…

Why does the water in the tube go down when you push on the sides of the plastic jar?

Why it happens…

The volume in the plastic jar is less

When you squeeze the plastic jar…

Molecules have less room to move around so they bang into each other and the sides of the jar more often

Increases the pressure in the plastic jar

Why it happens…

The air inside the top of the glass bottle is also compressed

When you squeeze the plastic jar…

1. Air takes up less room

2. leaving an empty space in the glass bottle

3. Which can not change its shape

Why it happens…

When you squeeze the plastic jar…

1. When the volume of air in the glass bottle is compressed

2. The water flows up the straw to fill the empty space

Question 2- Page 45(LB)

• Decreased the volume in plastic jar and increased air pressure

• Air in the glass bottle is compressed - leaving an empty space in the glass bottle

• Water flowed from the tube to fill the space previously filled with air in the glass bottle

Question 3- Page 45 (LB)

• There would be less pressure

• Air in the glass bottle would expand

• Pushing the water up the tube

Multimedia

• Gas in a syringe simulation

• Compare the syringe system to the pressure indicator you built.

Density

• What happened to the volume?• It decreased

• What happened to the number of molecules?• Stayed the same.

Density

• If the number of molecules stayed the same, what happened to the total mass of the molecules?

• It stayed the same.

• If the volume decreased and the mass stayed the same, what happened to the density of the air?

• The density increased