Today we were talking about acids. We know that they are bad for our teeth and that they often smell very strongly and may be in some of our foods or drinks. We wanted to find out how to tell whether a drink was an acid or not. This is what we needed:
A bowl of very hot water, a red cabbage, a knife and chopping board, lots of empty cups, a jug and lots of drinks and solids to check.
Teacher cut the cabbage and put the pieces into the bowl of hot water. She left this to cool. When it was cool, she used the jug to pour the now purple coloured water into each empty cup. (It is the colour from the red cabbage that turns the water purple, the cabbage in the water turned white when the colour went in the water).
Now came the fun part - we got to guess what colour the water would change when we put our drinks into the water.
Here are our results: Vinegar, lemon juice, cranberry juice, lemonade, apple and blackcurrant juice, ribena, orange juice and apple juice all turned the cabbage water red or pink. These all have acid in them - we need to brush our teeth if we drink these!
We found that wash-up liquid and bread soda both turned the water a blue-green colour. These are alkalis.
Finally we found that a drink of water didn't change the colour at all. Water is neutral. Red cabbage is a natural PH indicator and can tell whether something is an acid, an alkali or neutral. We can't wait to try this at home with our parents.
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