1. Pop Rockets PURPOSE: To predict and measure the effects of the amount of oxygen on the combustion of hydrogen gas, and show that real reactions really do work best when balanced. BACKGROUND: Hydrogen gas is highly flammable, and combusts with oxygen to make water. O 2 + 2 H 2  2 H 2 O

2. Pop Rockets PREDICTIONS: O 2 + 2 H 2  2 H 2 O The chemical equation tells us that for every 1 molecules of oxygen gas and 2 molecules of hydrogen gas, we’ll make 2 molecules of water. In pictures: Energy is released ONLY when water is made. The more water made, the more energy released — and the bigger the explosion.

3. Pop Rockets But what happens if we have a different number of molecules? QUESTION: What can we make with 4 O 2 and 2 H 2 ? ?

4. Pop Rockets ANSWER: We get two water molecules — but three of the oxygen molecules are leftover. So, some of the available energy was not released!

5. Pop Rockets Beginning Amounts  Ending Amounts O2O2 H2H2 H2OH2OO2O2 H2H2 06??? 15??? 24??? 33??? 42230 51??? 60??? Now, as lab groups, try to figure out all the other possible combinations of six total molecules. You may split molecules in half if you need to …

6. Pop Rockets Beginning Amounts  Ending Amounts O2O2 H2H2 H2OH2OO2O2 H2H2 06 15 24 33 42 51 60 Now, as lab groups, try to figure out all the other possible combinations of six total molecules. You may split molecules in half if you need to …

7. Pop Rockets Beginning Amounts  Ending Amounts O2O2 H2H2 H2OH2OO2O2 H2H2 06006 15203 24400 3331.50 42230 5114.50 60060 Now, as lab groups, try to figure out all possible combinations of six total molecules. You may split molecules in half if you need to …

8. Pop Rockets METHOD: Teams will fill pipette bulbs with different fractions of hydrogen and oxygen gas produced by a fuel cell. You will then launch the bulbs using a piezoelectric igniter, measure the distance traveled, and judge the loudness of the pop. All teams will start with a half-and-half mix (3 parts O 2 & 3 parts H 2 ), and then do two other combinations as assigned.

9. Pop Rockets STEP 1: Water Go to the water filling station and fill your pipette bulb with water using the syringe and fill tube. STEP 2: Oxygen Go to the “gas station” and fill your pipette with your assigned amount of oxygen (in sixths of a bulb).

10. Pop Rockets STEP 3: Hydrogen Fill the pipette bulb the rest of the way with hydrogen, and “cap” the bulb with your finger. Pipette Bulb Fill Tube Insert the fill tube into the bulb and allow the gas to displace the water — about 1 drop per second.

11. Pop Rockets STEP 4: Launch When teams are ready, the bulbs will be launched using a piezoelectric igniter. All teams will judge the relative loudness on a scale of 0 – 10, with the loudness of the half & half bulb (which must be launched first) being defined as “5”. Your team will also measure the distance of flight for your bulb (by counting tiles). Teams will enter their results in the table that follows.

12. Pop Rockets RESULTS: O2O2 H2H2 Pop (0-10)Distance (tiles) 06 15 24 33 5 42 51 60

13. Pop Rockets RESULTS: Averages from 2012 – 2014 O2O2 H2H2 Pop (0-10)Distance (tiles) 060.0 1514.5 2419.3 33 5 19.9 4217.9 518.6 600

14. Pop Rockets RESULTS: Averages from 2012 – 2014 O2O2 H2H2 Pop (0-10)Distance (tiles) 0600.0 156.214.5 246.319.3 335.019.9 423.117.9 5108.6 6000

15. Pop Rockets

16. QUESTIONS: See handout …