Blog Activity 7: Gases

Complete the Clicker Questions on Gas Laws in the Teaching Idea “Concept Questions for Chemistry using PhET” posted by Trish Loeblein. Use the PhET simulation Gas Properties to help answer the questions. (https://phet.colorado.edu/en/simulation/gas--‐properties) On your blog post the answers with your scientific explanations to these questions.

 

1. There are 2 balloons in a room. They are identical in size and material. One balloon is filled with air and the other balloon is filled with Helium. How does the pressure of the air balloon compare to the pressure of the Helium balloon. The pressure in the air balloon is:

•   C: (greater) The pressure in the air balloon is greater because the air balloon is denser. The helium is less dense meaning it has less pressure. 

2. How does the pressure in the Helium balloon compare to the pressure of the air in the room? The pressure in the Helium balloon is

• A: (less) The pressure in the Helium balloon is less than the pressure of the air because that is what makes the helium balloon float into the air. If the pressure was the same as the air, or greater than the air, the balloon would not float. 

3. How do the number of air molecules in the air balloon compare to the number of He atoms in Helium balloon?

• A: (less) The number of air molecules is less than the helium atoms because air molecules take up more space due to the fact that air molecules are bigger than helium molecules. 

4. How does the average speed of the Helium molecules compare to that of the air molecules?

The average speed of the He molecules is

• C: (greater) The speed of the helium molecules is faster because the helium molecules are smaller and are able to move around faster and in smaller openings to travel around inside of the balloon.  

5. What will happen to the pressure if temp is held constant and the volume is decreased? 

• B. (Pressure goes up because more collisions are happening, but same force per collision) On the simulation, when I decreased the volume, the pressure went up. More collisions are occurring, but the force per collision is the same because there is less room for the molecules to move around in in the container. Boyle’s Law says that at constant temperature, the volume of a gas is inversely proportional to its pressure. 

6. You are flying from Denver to Boston, and you bring along a ½ full bottle of shampoo that was well sealed before you left Denver. You land in Boston and proceed to your hotel. The number of air molecules within the shampoo bottle: 

• B: (has stayed the same) Since the bottle was sealed, the change in the altitude, and therefore the change in air pressure, in Boston did not affect the number of molecules inside the bottle.  

7. If the walls of the shampoo bottle are strong and rigid so that the bottle has the same shape as before you left, how does the pressure of the air inside the bottle compare to the pressure of the air in Denver? 

• B: (equal to) The bottle originated in Denver, so the pressure inside the bottle is the same as the pressure of e air in Denver 

8. How does the pressure inside the bottle compare to the pressure of the air in Boston.

•  A: (less than) The pressure in Denver is lower since Denver is at a higher altitude. Boston has a higher pressure since it is at a lower altitude which makes the pressure inside the bottle less as it was filled in Denver.  

9. If you had a water bottle with very soft sides. When you open your suitcase in Boston, the bottle would look 

• A: (squished) This occurs because the pressure in the air is greater than the pressure in the bottle. This is pushing the bottle inward until the inside molecules can exert the same amount of pressure outward.