To understand substances properties (e.g. density).
1. Fill the bottle up about 1 quarter with water.
2. Pour the vegetable oil in the bottle until it is almost full. You may want to use a measuring cup with a spout or a funnel. You may have to wait a couple of minutes for the oil and water to separate.
3. Add a few drops of your favourite food colouring. Watch as the colour sinks through the oil. Did your drops of colour mix with the water immediately or float in between for a few minutes?
4. Break your fizzy tablet in half and drop part of it into the bottle. Get ready, here come the bubbly blobs!
5. You can even get a flashlight, turn off the lights and drop in another half tablet. This time shine the flashlight through the lava lamp while the blobs are bubbling
Provide guidance and facilitate getting materials (plastic bottle, food colouring, flashlight etc.).
The oil floats on top of the water because it is less dense or lighter than water. The food colouring has the same density as the water so it sink through the oil and mixes with the water. When you add the tablet it sinks to the bottom then starts to dissolve. As it dissolves it makes gas, carbon dioxide. Gas or air, is lighter than water so it floats to the top. The air bubbles bring some coloured water with them to the top.
Provide assistance in mixing things up and explain as you go.
This activity was created by Sally-Anne Yeomans, PGCE student in summer term 2020
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