ingridscience

Prepare the rocket by drilling through the cork.

Add water to the rocket, insert the cork containing the needle attached to the pump.
Put it in the stand/stand upright.
Ask everyone to stand well back, as it will take off with no warning at high speed.
Pump air into the rocket until it takes off.

The pressure of air in the bottle above the water increases until it is too high to be held in by the cork.
As the cork flies out, the water flies out too, helping project the rocket higher.

Experiment with amount of water for the best flight.
Too much water means there is too much weight. Too little means there is not so much water shooting out to project the rocket higher.

Lots of great explanation, plus how to construct on the Naked Scientists website: http://www.thenakedscientists.com/HTML/experiments/exp/water-rockets/

Add a little ethanol to the jug.
Swirl it around to coat the sides and evaporate into the volume of the flask.
Ignite at the top.

Discuss the chemistry of the reaction:
ethanol + oxygen -> water and CO2
Model the chemistry of the combustion reaction

Light the ping pong ball and watch it burn.

The ping pong ball is fuel for a combustion reaction: it combines with oxygen to release heat and light. Carbon dioxide and water are made, along with an ash.

Once the combustion reaction starts, the heat it generates keeps the reaction going.

Either build the starting molecules, or ask students to make them: one ethanol molecule and three oxygen molecules.

Tell/remind students that ethanol is a fuel that burns in oxygen, and that when the fuel and oxygen chemically react their atoms come apart and recombine into new molecules.
One of those new molecules is water (H2O), and it makes three of them.
Ask students to pull apart their ethanol and oxygen molecules, and rearrange them to make three water molecules.
Then tell them that the remaining atoms and bonds make the other reaction product. There are two identical molecules of this second product.
Give them time to use up all the remaining atoms and bonds to make two identical molecules. With time, they should arrive at CO2, or carbon dioxide.

So when ethanol (or other fuels) burn in oxygen the reaction products are water and carbon dioxide.
Sometimes carbon (as soot) is also made, when not all the carbon combines with oxygen (called incomplete combustion).

Additional information on the flames that are often present during combustion:
The flame is a mixture of hot gases, primarily CO2, water vapour, oxygen and nitrogen (nitrogen comes from other materials that burn).
Energy in the flame excites the electrons in some of the transient reaction intermediates such as the Methylidyne radical (CH) and Diatomic carbon (C2), which results in the emission of visible light (blue and green for these radicals) as these substances release their excess energy.
https://en.wikipedia.org/wiki/Flame

Fill the bottle with water, with a finger over the hole, and hold it over a sink.
Let the water stream out of the hole. Ask a student to shine the laser through the bottle and into the start of the stream.
The laser light will be reflected from the sides of the inside of the stream, so it stays inside the stream of water even as it curves, so lighting up the water stream. There is a point where the stream curves too steeply for the internal reflection to continue.

https://www.youtube.com/watch?v=ifbCsha7Syc

Give students pocket lasers, small mirrors, and tape.

Ask them to reflect the laser around the room.

It is more challenging than expected, as a slight change of angle of the mirror will change the direction of the laser dramatically.

Very fun, but very dusty for other objects in the room: clap cornstarch in the air to visualize the laser beams. Students can design a challenge where they have to crawl under and climb over laser beams without touching them.