Chemical Equation

Three things are usually required for a chemical explosion: a chemical reaction that occurs very rapidly, a large increase in gas pressure, and a confined-reaction vessel in which the pressure of the gaseous products can increase to a point that the gases break violently out of the container. In this chemistry and physics science fair project, you will use the combustion of ethanol to provide energy for a small explosion. The chemical equation that describes the combustion of ethanol is shown below. (Note: Hover over the equations in this Introduction with your cursor to view enlarged formulas.)

Equation 1:

C2H6O+3O2→3H2O+2CO2+heat
Ethanol: C2H6O
Oxygen: 3O2
Water: H2O
Carbon dioxide: CO2
The chemical equation states that ethanol (C2H6O)
The key point about this equation, for the purposes of this science fair project, is that it clearly shows the mathematical relationship between pressure, amount of gas, and temperature. The pressure, P, is directly proportional to n, and T. If you double P in the equation, keeping V, n, and R the same, then T will also double. The same goes for n and P. The equation is precise only for "ideal" gases in equilibrium with their surroundings, which is not the case in an explosion. But the ideal gas equation is a useful approximation of this real-world experiment.

A version of the experimental setup is shown in Figure 1. The apparatus consists of a piece of wood with the top of a film canister glued onto it. The metal ends of a grill spark igniter are passed through a hole in the wood and through the film canister top. The metal ends will deliver a spark when the red button is pushed. When you add a fuel to the film canister and attach it to the plastic top that is glued to the board, a spark will ignite the fuel and send the canister flying. The fuel used to launch the canister is Binaca breath spray (ethanol and isopropane). A tire pressure gauge is used to measure
Note from Equation 3 that you can determine launch velocity if you know the flight time. Time of flight is easy to measure; just use the stopwatch to time the interval from launch to landing. Once you have calculated the launch velocity, you can calculate the maximum height the canister flies using Equation 4. Remember that the equations are approximations and do not take into account the air resistance. You will use the trajectory equations to determine the launch velocity of the canister, its maximum height, and its kinetic and potential energy.

The kinetic energy of the canister gives you a minimum value for the chemical energy of the combustion reaction. It is a minimum value because energy is lost as heat, friction, and in other ways. As you work through the procedure, consider where the energy is flowing. The overall flow of energy when the canister is launched straight up follows this sequence:

Chemical energy: Energy released as heat causes an abrupt pressure rise in the canister.
Kinetic energy: The canister is launched upward.
Potential energy: This reaches a maximum at the maximum height. It returns to zero when the canister