Purpose
To illustrate a synthesis reaction involving reactants in specific proportions.

Materials

• Hydrogen gas (or Calcium metal and water)
• Oxygen gas (or hydrogen peroxide and manganese dioxide)
• 500 mL plastic pop bottle
• 500 mL graduated cylinder
• Plastic dish tub or displacement (pneumatic) trough

Safety

• Read the MSDS/WHMIS sheets for all chemicals before using them
• Wear chemical safety glasses
• Noise warning for students
• Explosive (H2) and flammable (O2) gases in use
• Ensure gas cylinders are secure
• Ensure no one is in the trajectory of bottle (may veer to the left or right)

Procedure

1. Fill an empty 500 mL plastic pop bottle completely with water.
2. Determine the volume of the entire pop bottle by measuring the amount of water in the bottle using a graduated cylinder.
3. Calculate two thirds of the total volume and then using a graduated cylinder pour that volume of water back into the empty bottle.
4. Mark the water line using a marker.
5. Completely the fill the bottle with water and then recap the bottle.
6. Place the opening of the bottle under water in a dish tub or displacement trough and then remove the cap. Ensure the bottle is inverted and completely full of water.
7. Fill the bottle with hydrogen gas from a hydrogen gas cylinder until the marker line made in step 4. The gas will displace the water in the bottle.
8. Displace the remaining water with oxygen gas from an oxygen gas cylinder.
9. Recap the bottle while the opening remains under the surface of the water in the dish tub.
10. Place the bottle on a ramp (use binders or books) at one end of the room with the students off to the side.
11. Warn the students that a loud bang is possible so they can take the appropriate measures.
12. Ensuring no one is in front of the bottle and a safety shield is to the side of the bottle where the students are, remove the cap and quickly place the flame of a barbeque lighter near the opening.

Results
A loud explosion occurs which rockets the bottle across the room.

Follow-up Teaching Notes

• A very loud bang is produced and the bottle will shoot across the classroom
• Varying the ratio of hydrogen to oxygen from 2 to 1 will decrease the distance and sound of the bottle rocket.
• Reaction occurring 2 H2 (g) + O2 (g) –> 2 H2O (g) + energy.
• Have a student examine the bottle to feel the heat generated.

Connections
Synthesis reaction, balancing equations, combustion.

Disposal/Clean-up
The empty plastic bottle can be recycled.

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