This was a fun experiment, I remember doing it years ago but Ebi-kun doesn't remember at all and of course his understanding of the world is much great now he is older, so the whole experiment was like a new take on it all.
What you need:
4 clear glasses
Soda water and 3 other liquids, we used milk, tap water and vinegar
Food colour to distinguish the liquids
Pieces of paper & a pencil
1. Fill each glass about 3/4 full with each of the liquids, leave the soda water until you are about to do it in the experiment.
2. Label each glass with it's contents.
3. Ask the child to predict what will happen when they put a raisin the glass (they will probably just say sink or float). Write the prediction on the name cards.
4. Ask the child why each glass has three raisins. The reason is that you want to introduce the idea that scientific research is tested several times to cross out any flukes or accidents. You can ask what will happen if the first raisin in the water sinks and the second one floats? Does this mean raisins sink or float in water?
5. One glass at a time (leave the soda until last) drop in the raisins and note the result, was the prediction from the start right or wrong? What happened with the soda water? And Why?
The bubbles attach themselves to the raisins, which causes the raisin to float, when it hits the surface, the bubbles pop so the raisin sinks again, this will repeat until the soda goes flat.
***NOTE: If the soda water is not very fizzy, add some baking soda to get more bubbles in there. If you want to get messy try mixing the vinegar and soda, do it on a tray or in the sink though.
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