Gas Pressure Activity Questions

Gas Pressure Activity

Objective: Pressure is caused by the number of collisions between molecules and the force of these collisions. When there are more collisions, the pressure is higher. There are three things that can affect the number of collisions.

            1) size of the container

            2) temperature

            3) number of molecules

You will look at how these three factors affect the number of collisions and therefore affect the pressure of a gas.

Procedure: For each of the following parts, you will need a long rope and four students to hold the rope in a square shape. Each student holding the rope will count the number of “gas molecules” (students) that collide with the wall of the container during a time period of one minute for each trial.

Gas molecules should remember the following:

1)     Gas molecules travel in straight path until acted upon by the wall of the container or another gas molecule. They do not turn to avoid or cause a collision.

2)     Gas molecules move at constant random motion. So you should not change your speed or stop during the duration of a trial.

3)     Gas molecules are not attracted to or repelled by each other. So you should not change directions to hit your classmates. 

1. DATA & ACTIVITY

PART A

Container size and pressure: Gas molecules should move at room temperature.

Container Size	Number of collisions         Trial 1                              Trial 2                                Average
Small container
Large container

PART B

Temperature and pressure: Gas molecules should speed walk for high temperature and walk slowly for low temperature.

Temperature	Number of collisions         Trial 1                                Trial 2                                 Average
High Temperature
Low Temperature

PART C

Number of molecules and pressure

Number of Molecules	Number of collisions         Trial 1                               Trial 2                             Average
5 molecules
10 molecules

2. Analyze your data:

1)      What two things cause pressure in gases?

2)      Out of the three factors that affect pressure, which do you think would affects the pressure the most? Why?

3)      As you increase the size of a container, what happens to pressure?

4)      As you decrease the number of gas particles, what happens to pressure?

5)      As you increase the temperature, what happens to pressure?

6)      As temperature decreases, what do you think would happen to the volume of a balloon?

7)      Draw two pictures each of Part A & Part C, drawing two boxes for each of the two different situations in the activity. Make sure to show the molecules in the boxes accurately.

 

Part A                                                                                    Large

Small                                                                                     container

container

Part C                                                                                    10

5                                                                                              molecules

molecules

Homework for 2/9

1) pg. 480 #1-2, 4 c-d, 5 a-b & d, 6 a-b & d, 7 a-c
2) Review session for Chpt 10 after school today
3) Finish all labs (4 in class labs & 3 take home labs)
4) Assessment make up due Wednesday!

Homework for 2/5

1) pg. 446 ex. 13.1, pg. 448 ex 13.2,  pg. 457 #3-4
2) Make sure all labs are completed!

Energy Value for Nuts

Energy Value of Nuts

Problem: How much heat is available from the combustion of peanuts, almonds, and other nuts. Can this heat be measured?

Objective:  When you eat food, your body is actually “combusting” the food.  The fat, protein and carbohydrates react with the oxygen in your body to produce carbon dioxide and water.  You will choose three types of nut to burn and measure the amount of energy released via water being heated by flame.  Unfortunately, we will lost a lot of heat to the surroundings and we also will have to heat the aluminum can as well. 

1. Hypothesis: Predict which nut—peanuts, cashews, almonds, brazil nut or pecans—will furnish the greatest amount of energy per gram. Explain your hypothesis.

2. Data Table:

	Trial #1—type of nut ___________	Trial #2—type of nut _________	Trial #3—type of nut _________
Mass of nut (initial)
Mass of can
Volume of water
Temperature initial of water
Temperature final of water
Mass of leftover nut

3. Determine the change in mass of each nut from before and after combustion.

     Mass of nut (initial) – mass of leftover nut =  mass of nut that combusted

4. Determine the change in temperature of water (and therefore, also the can) before and after combustion.

          Temperature final – Temperature initial = Temperature change

5. Determine the heat absorbed by the water, using the equation Q = s x m x DT

          (specific heat for water is 4.18 J/g×C°)

                                                                                                             

6. Determine the heat absorbed by the can, using the equation Q = s x m x DT

          (specific heat for aluminum is 0.9 J/g×C°)

7. Determine the total heat absorbed by the water and the beaker.

          NOTE: This is also equal to the heat released by the nut.

8. Determine the total heat released per gram of nut.

          Divide by the total heat by the total gram of nut that combusted.

9. Summary Table

	Trial #1—type of nut	Trial #2—type of nut	Trial #3—type of nut
Mass of combusted nut #3
Change in Temperature (DT) #4
Heat absorbed by the water #5
Heat absorbed by the can  #6
Total heat absorbed #7
Total heat released per gram of nut #8

10. Critique the procedure used in this experiment. Do you expect the procedure to give an accurate energy value for the nuts? Explain your answer.