Boyle's+Law+and+Changes+in+Pressure

= Boyle's Law and Changes in Pressure = Seth McNaughton - __ slm5478@psu.edu __ Clint Mills - __ cbm5073@psu.edu __

__Standards__ o Properties of objects and materials § Objects have many observable properties, including size, weight, shape, color, temperature, and the ability to react with other substances. Those properties can be measured using tools, such as rulers, balances, and thermometers. o Explain concepts about the structure and properties of matter § Predict the behavior of gases through the use of Boyle's, Charles' or the ideal gas law, in everyday situations
 * Grade 7 - Boyle's Law and Changes in Pressure**
 * National Science Content Standard B (page 123-127)
 * Pennsylvania 3.4.10.A

__Objectives__
 * Students will be able to explain why certain things expand in a vacuum
 * Students will be able to explain the basics of Boyle's Law

__Big Idea__ Although not immediately apparent, all objects on earth have pressure exerted on them from the atmosphere. Objects, in turn, press with a force that exactly cancels out the air pushing in on them. This is especially noticeable with balloons (obviously filled with air), and marshmallows (which are sugar and air). When the vacuum pump is used, the pressure exerted on the marshmallows from the outside air decreases, while the pressure exerted by the air inside the marshmallows is the same. The pressures do not cancel out and the marshmallows expand. When the pump is turned off, the marshmallows shrink to a size smaller than normal. This happens because, when the marshmallows are expanding, some of the air inside the marshmallows escapes. Boyle's Law says that if temperature is kept constant in a closed system, pressure and volume are inversely proportional (P1V1=P2V2).

__Administrative Considerations__ Students will not be permitted to eat the marshmallows at any point in the lesson (even after they've become useless and shrunk). Only the teacher will handle the vacuum pump and glass lid that goes on the vacuum pump.

__Materials__
 * 1-2 balloons per group (in case it pops)
 * 7 marshmallows per group
 * Wire (for building the structure of the marshmallow man)
 * Marker (for drawing a face)
 * Vacuum pump and chamber

__Set-Up__ The vacuum pump will need to be moderately close to a power source. If there are other groups in the same room, it might be a good idea if this station is further away from others (due to noise). The balloon will be partially inflated while the students are there. Students will be shown that the balloon is tied, and cannot be filled any further. The balloon is placed in the vacuum pump and the pump is turned on, let to expand, and then the air is let back into the chamber allowing the balloon to decrease once again. Students will work in a group to build a man out of marshmallows and wire. This man is placed in the vacuum chamber and the air removed once again.

__Body of the Lesson__ a) **Predict (3 min)** a. "Has anyone ever been in outer space?" (Answer will be no. If they answer yes, they're lying. But, at least you've found a confident kid who may have a good imagination!) i. "Although no one's ever been to space, do you know what's out there?" or "What makes space different from earth?" (There's no air out in space) 1. "Why does it matter that there's no air in space?" (Could get a bunch of different answers) b. Well today we're going to simulate what would happen if things were slowly brought into space. Let's start with a balloon. If I were to blow this up, what do you think would happen if we brought it with us to space? (Perhaps grow, shrink, nothing...or some other random answers - then blow up the balloon). i. Give me a thumbs up if you think the balloon will get bigger, a thumb in the middle if you think nothing will happen, and a thumbs down if you think it'll shrink. Don't look at each other, it's ok if you're wrong, none of us have been to space! c. This here is a vacuum pump. It sucks the air out of the glass chamber which is similar to what space would be like.

b) **Observe (3 min)** a. Let's observe as we place the balloon into the glass and take the air out. b. "What's happening?" c. (Let sit there for a bit) d. "What do you think will happen if we let the air back in?" Will it stay the same size? e. (Let the air back in)

a. "Why did the balloon grow, and then return back to the same size it was? Did some mysterious invisible man come and add more air inside and then take it away?" b. Although not immediately apparent, all objects on earth have pressure exerted on them from the atmosphere. Objects, in turn, press with a force that exactly cancels out the air pushing in on them. This is especially noticeable with balloons (obviously filled with air. When the vacuum pump is used, the pressure exerted on the balloon from the outside air decreases, while the pressure exerted by the air inside the balloon is the same. The pressures do not cancel out and the marshmallows expand. When the pump is turned off, the balloon shrinks to the same size. c. So the balloon is trying to share some of its pressure with the low pressure, or no pressure, which shows us that pressure likes to be balanced. d. Pressure and volume are inversely related. When pressure increases, the volume decreases.
 * c)** **Explain (2 min)**

d) **Predict II (and build 7 min**) a. We've seen what happens with a balloon, but how about marshmallows? They aren't quite as filled with air. b. Give me a thumbs up if you think the balloon will get bigger, a thumb in the middle if you think nothing will happen, and a thumbs down if you think it'll shrink. c. Well, we're going to build a marshmallow man to find out! You have 7 marshmallows as a group and this wire to build a marshmallow looking man. Use the wire to be the frame for him, and the marshmallows to be his head, hands, and feet/legs.

e) **Observe II (3 min)** a. Has anyone here ever been on a plane? i. "This might be similar to how we would react if the planes weren't pressurized. However, they keep the place where you are at a more constant pressure so you don't experience the same force that you would otherwise."

f) **Explain II (2 min)** a. If we were going into space, could we go dressed as we are right now? No! We'd need to wear a space suit! This helps regulate the pressure for our bodies so we don't end up like the marshmallow man. b. So things in high pressure like to go to high/__low__ pressure? Low, exactly. This can help us explain syringes, weather, and many other really cool things. c. Extra time: i. Respiration (Breathing) - How many of you guys breathe? (The same guy that's been to space probably doesn't breathe either). You move your diaphragm (a muscle below your lungs) downward which increases the volume in your lungs. This creates a low pressure system inside you, which causes the air to rush from higher outside pressure through your mouth into lungs. When you breathe out, you contract your diaphragm (making your lungs smaller) and then causes the air to rush outside of you. 1. Wind knocked out of you - blow to diaphragm which temporarily paralyzes the diaphragm so you can't expand or contract your lungs ii. Syringes/pipets - when you pull on them, you're expanding the volume, which decreases the pressure. We know that things like to go from high pressure to low pressure, so you can suck up whatever you put the syringe in - like water. When you want to release the water, you push on the end of it. This decreases the volume, and increases the pressure. So outside the syringe is low pressure in comparison and the water leaves the syringe.