Yesterday we agreed to try and find out what makes a mixture of vinegar and bicarbonate of soda 'explode' (if you are not sure what I am talking about, take a look at Per's Blog entry on 'My Paper Mache Volcano').
Fiona, our star 'finder-outer' told us.
'Vinegar and bicarbonate of soda,' she explained, 'are opposites and when they are mixed together they kind of have a fight and a gas is made which bubbles and fizzes.'
Well of course we had to try it out to see. First a dollop of bicarbonate of soda. Next a dribble of vinegar. Give it a swirl and.....wheee.....a chemical reaction!
bubbly bubbly bubbly
So far - so much fun!
Now down to the serious stuff. We found some litmus paper lurking at the back of the cupboard; this is a special paper that changes colour when things are acid or alkali or in the middle (which we call neutral).
First we dipped it into the vinegar. It turned reddish orange
Next we dipped it into the bicarbonate of soda. it turned bluey green
Finally we did the 'lick' test. Lick is 'neutral' - it turned the paper green
Vinegar is what is called an acid and bicarbonate of soda is an alkali.
Now what to do with our new-found knowledge? Tum tee tum.....
Remember all those white materials; the ones we tested to see if they dissolved or not? Well how about finding out whether they are acid or alkali or neutral?
We mixed salt, sugar, washing powder, white powder paint and chalk with water to make 5 solutions. We dipped litmus paper into each solution and recorded our results in a table.
Take a look at our results. Were you surprised by any like we were?
We had thought that sugar might be acid because we know it can make holes in teeth.
We weren't expecting washing powder to be alkali; we thought it would be neutral.
What other things could we test?