INVESTIGATING GASES

Boyle’s Law

WORKING WITH A SYRINGE

Start with the plunger all the way into the syringe. Try pulling out and pushing in the plunger. Now “plug the end” with your finger and try to pull and push the plunger

Record on your paper what you notice about each situation.

Step 1) no air Unplugged Plugged with finger

Push plunger in

Pull plunger out

Now pull out the plunger so there is some air in the syringe. Try pushing in the plunger and pulling out the plunger.

Repeat but this time plug the opening with your finger first.

Step 2) Air Unplugged Plugged with finger

Push plunger in

Pull plunger out

NOW LET’S ADD A MARSHMALLOW

Take two marshmallows and draw a face on each

Remove the plunger from the syringe

Place one marshmallow in the syringe and replace the plunger

Push in the plunger to force out as much air as possible without squeezing the marshmallow

CONT’D Plug the syringe with your finger Pull on the plunger, hold it in the

“out” position and record your observations

Predict what will happen when you release the plunger. Record

Release the plunger and record your observations

Repeat several times so everyone gets a chance to “play”

WHY DID THE MARSHMALLOW BEHAVE THIS WAY?

YOU JUST LEARNED BOYLE’S LAW Boyle’s law states that volume of a

gas varies INVERSELY with pressure at constant temperature and constant number of gas molecules.

If pressure decreases (pull plunger out) = volume increases (marshmallow got bigger)

If pressure increases (push plunger in) = volume decreases (marshmallow got smaller)

RULES FOR GASES When discussing gases, one

must always specify theTemperatureVolumePressureQuantity (number of molecules)All of these will affect the way the gases behave.

QUICK QUIZ Imagine a marshmallow sealed on Earth

in a steel container at 1 atm pressure. Predict what change (if any) would occur in the volume of the marshmallow if the container were opened in each of the following situations (assuming not temperature change):1. In a space shuttle: weightless but

pressurized at 1 atm2. On a space walk: weightless with 0 atm

pressure3. On a deep-sea dive: at a depth of 1000 ft

which 4 atm of pressure