💦💨 Convection in liquids and gases
Ask your parents, grannies, bigger sister or brother, or any other older relatives to help you with these activities below.
👀🔍 Observation 1
You need:
- an aquarium or other large transparent container filled with water at room temperature;
- a large bowl (or 2 smaller ones) that can be putted in the aquarium;
- 2 small plastic boxes with lids (for example plastic boxes of Kinder chocolate eggs);
- a hammer, nails, knife, hot boiled water, iced water
- red and blue food coloring
Place the large bowl (or 2 smaller ones) in the aquarium, bottom-up, so that they form a flat surface.
Make a hole in the lids of the small plastic boxes (using a hammer and nail). Use a knife to make the hole bigger, like a slit about 1 cm long. Fill one of the small boxes with boiling water. Drop red food coloring into it.
Now fill the other plastic box with iced water. Drop some of the blue food colorings into it.
Place the 2 plastic boxes on top of the large bowl.
Push the two small boxes lying sideways in the aquarium. They immediately begin to release the water that is in them. What is happening?
If the experiment is performed correctly – the red water from the hot plastic box rises to the surface of the water in the aquarium, while the blue water (from the cold box) sinks to the bottom.
👀🔍 Observation 2
You need:
- a balloon, a pot of boiling water, and an empty glass bottle.
Attach the balloon over the neck of the bottle. Put the bottle in a pot of boiling water. What happens to the balloon when the air molecules that were in the bottle start to heat up?
Yes. The hot water from the pot heats the air in the bottle. When it warms up, its pressure rises and begins to go up, causing the balloon to inflate.
Remove the bottle from the pan and allow it to cool down.
What’s happening?
After a while, the inflated balloon dropped as the bottle cooled. Have you noticed that the walls of the bottle are also warm to the touch? Why? When placing the bottle in the boiling water, its walls come into direct contact with the hot water molecules. What did we observe? This is thermal conductivity through direct contact with the heat source.
✅🧑🎓 Check your skills:
- What is convection?
- Say 3 examples of convection in liquids and gases around you.
- Why the red water from the hot plastic box rises to the surface of the water in the aquarium?
- Is the hot air heavier that the cold air?
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