Allison from High Touch High Tech Vancouver found some great ways that you can become a magician! The following little ‘tricks’ will appear to be magic until you understand the science behind them. There’s an old saying that science begins with wonder, and getting your students to wonder how tricks like these work is an excellent way of getting them to want to know more about the science behind them. These simple science experiements are a fun & easy way to get hands-on!
Hot & Cold Water:
How can water be hot & cold at the same time?
You Will Need:
Three bowls or dishes: one containing cold water, one hot water, one lukewarm. Arrange the bowls in a row with the lukewarm water in the middle.
Safety note: Test in advance to make sure that the hot and cold water is not dangerously hot or cold. Pupils should be able put their hands in the bowls without discomfort or risk of scalding
Ask for two volunteers from the audience – I mean the pupils – and explain that you are going to perform a special bit of magic with three bowls of water. Ask each of your volunteers to roll up their sleeves. One dips a hand into the cold water, while the other does the same with the hot water. Leave the volunteers standing in place for a minute or so, while you explain to the class that these two bowls contain perfectly ordinary water, but the middle bowl contains magic water, which has the amazing property of being both hot and cold at the same time.
Then ask your volunteers to remove their hands from their bowls and put the same hand into the middle bowl. Ask: ‘Is the water in this bowl hot or cold?’ The pupil whose hand was in cold water should say ‘Hot’, while the pupil whose hand was in hot water should say ‘Cold’.
Ask them to take their hands out of the bowl, swap places and put their other hand into the opposite bowl. Again leave them with their hands in place for a minute or so, then again have them put the same hands into the middle bowl. This time they should give the reverse answers.
How It Works:
So how can the water be both hot and cold at the same time? Ask the children for suggestions, and they should tell you that because one child’s hand was in cold water to begin with, the lukewarm water would have seemed hot by comparison and vice versa. The point to establish is that the way we sense the world is relative; we become used to our surroundings, so how we perceive a different environment depends on where we approach it from. For example, go into the playground from a warm room and it might feel cold; go outside from a cold room and the playground would feel warm. Ask the children if they can think of other similar examples and to devise experiments to test their theories, such as going from a darkened room into a brightly lit one and vice versa.
The room is haunted… or is it?
You Will Need:
- Lemon juice
- A fine paintbrush or a cotton bud
- A source of heat, such as a naked light bulb, a candle, a Bunsen burner or perhaps an iron, if you have one available.
Safety note: always take appropriate precautions when using a naked flame or very hot objects in the classroom.
In preparation, use the paintbrush or cotton bud to write some messages on pieces of paper with lemon juice. Leave this to dry overnight and then distribute them around the room, along with several sheets of untreated paper.
Gather the pupils together and tell them that you have discovered something amazing – that your classroom is being haunted by a mysterious ghost. They will probably dispute this, so tell them you can prove it; you will ask the ghost to make a message appear on a blank piece of paper. Hold up one of your prepared pieces of paper to your heat source (or iron it if you’re using an iron). The ghostly message will slowly appear as if by magic.
Safety note: be careful not to burn yourself or set fire to the paper!
You can then ask the pupils to find the other pieces of paper you have hidden around the class and you can test each one in turn to discover whether the ghost has left any more messages.
How It’s Done:
Tell the class that of course it wasn’t a ghost who was writing, it’s all down to science again. Can they work out what really happened? Explain that all living things contain carbon, so if you write on paper with a clear juice from something once living, it will char and turn into black carbon when heated. The writing was made with lemon juice, which is invisible once it dries, but when it was heated enough, the carbon in it was released and it became visible. As an extension activity, you could have the pupils make invisible writing with other organic liquids, such as milk or onion juice, and see if the same thing happens.