Rubber bands? Check! Ice block sticks? Check! A plastic spoon? Check! You’ve got all the materials you need to make an easy homemade catapult.

Catapults are ancient weapons that were originally designed to hurl rocks at your enemy. They were first used by the Greeks way back in 500 BC.

From a scientific point of view, catapults are cool devices that change potential energy into kinetic energy. Potential energy is energy that is stored. Think of the spring in a jack in the box before you open the lid - that spring has potential energy. Kinetic energy is used when an object moves. So when we push down on the plastic spoons, we’re creating potential energy. When we let the spoon go, the energy becomes kinetic energy and our little balls of tinfoil go flying!

We’ve been exploring our past in Kahikatea. A couple of weeks ago we were looking at old copper coins, including a whole lot of ten cent pieces. Copper coins get very dull and tarnished. They react with the oxygen in the air around us which makes them get covered in stuff called copper oxide.

We discovered that taco sauce was brilliant at cleaning copper coins. By submerging our coins in the sauce for about 20 minutes they went from dull to shiny! Next, we wanted to find out why this was happening? What was the magic ingredient or ingredients in taco sauce that ‘ate’ the copper oxide off the coins?

Taco sauce is basically a tomato sauce or paste mixed with vinegar and some salt.

Our class then went about testing mixtures to find out what made the best coin cleaner. The winning ingredients were salt and vinegar.