hot air rising
Thursday, October 29th, 2009
We have been talking about solids and liquids using water and freezing it, see our ‘Water Shapes’ post under Science / Technology on September 13th.
The natural progression is to move onto gas and after a very heavy downpour of rain recently followed by brilliant sunshine the children noticed something strange was happening in the playground …
…’smoke‘ (steam) was coming off the shade sails …
… as well as the ground and play equipment!
Naturally this provided us with a great opportunity to talk about what happens when air and water heats up.
We showed the children boiling water and discussed what the steam is. Most children called it smoke at first. They noted how it went up into the air and didn’t fall down to the ground due to the hot air rising.
This led to a by the way discussion about how we need to get down low if we are caught in a fire and another opportunity to reinforce dialing OOO in an emergency following our recent police visit, see our ‘Stranger Danger‘ post under Incursions/Excursions on October 23rd – working with children is never a predictable thing!
Before illustrating how hot air rises, we showed the children an empty bottle and asked them what was in it. Most said nothing, a couple said air.
We placed a balloon on the top of the bottle and asked the children how we could blow it up from there. Naturally they said we could use our mouth, or a balloon pump but we asked them how we could do it without removing the balloon from the bottle.
Most had no idea but one clever child said to squeeze the bottle, which worked very well.
To illustrate how hot air rises and cold air falls we placed the bottle into some boiling water and slowly the air in the bottle warmed up and went into the balloon making it stand up straight – this always elicits lots of laughter, particularly from the mums!
We then popped the bottle into cold water and as the air cooled the balloon slowly shrank again. This can be repeated a few times until the hot water gets a bit too cool to warm up the air sufficiently.
As the children can’t do this experiement by themselves due to the boiling water factor, a science activity they can do which allows them to have fun with hot air rising, is to make spirals, just like the spiral snakes we made, see our ‘Wild Action and Spirals’ post under Science / Technology on October 27th. Hanging the spirals from a piece of string over a light bulb, the heat from the light warms the air, it rises up, and the spiral gently turns around.
It’s a good idea to turn the lamp on to warm up while the children are preparing their spirals.
Depending on which direction their spiral turned some of the children commented on their spiral winding up or winding down. One child even said “It looks like my snake is trying to climb up the string to get me!”
More great science! More great fun! More great play based learning!
