Wednesday, 16 March 2016

Investigations with heat

We are learning about heat.
Teacher had an empty bottle.  Well, it looked empty but we knew that it was in fact FULL...of air.
The air in the bottle was the same temperature as the air in the room around us.
We put a balloon on the top of the bottle and the balloon just flopped down the side of the bottle.
We know that when air is heated the molecules move around more and that warm air takes up more space than cold air.  We thought that the warm air might go into the balloon and inflate it.
It did!  When the air in the balloon was warm the balloon inflated and when the air cooled down again the balloon deflated again!
So, if warm air travels up into the balloon, does warm water also like to travel up (or does it like to go down)?
Teacher filled a little glass bottle with hot water and some red food colouring.
Then she put this bottle into a glass of cold water.
We could see the red warm water rise out of the little warm bottle and travel upwards in the cold water.
After a while, when the warm water cooled down, the red water sank to the bottom and mixed with the rest of the (non coloured) cold water.
Now we are sure that both warm air and also warm water like to travel upwards!
Finally we had a look at a burning candle.
What does the flame need to continue to burn?
We think it is air.
We wondered if the candle would continue to burn if the air all ran out.
We tried this:
We got a jam jar.  Although it was empty, we know that it was full of air!
Teacher lit the candle and then turned the jam jar over on top of the candle.
After a short while the candle went out (when there was no more Oxygen left to burn in)>
So, how much Oxygen was used up by the burning candle?
Well, here's how we can tell:
We put the candle sitting in a basin of coloured water.  Then the candle was lit and the jar was placed on top (balancing on two coins so that water could get into the jar).
When the flame used Oxygen there was a space (a vacuum) in the jar and the coloured water rushed up to fill the space.  We can tell how much Oxygen the candle used by looking at how high up the jar the coloured water rose.
What a lot of interesting things we learned about heat, hot air, hot water and candles today!

No comments: