Science Experiments

Fizzy Acids - what happens when you carbonate water

Sun, 10th May 2009

Listen Now    Download as mp3 Part 1,2 from the show Clean Water and Alien Invasions

What you Need

Soda syphon

A way of carbonating water - a soda syphon or sodastream

A Red Cabbage

Some red cabbage

A glass

Some glasses

What to do

Grate a small amount (2-3 leaves) of raw red cabbage and put it into a glass.  Add some tap water and then mash it up as well as you can.

Strain out the lumps of cabbage to produce a clear solution.  This is your pH indicator, it will behave like litmus changing colour depending on the acidity or alkalinity of your solution (to find out more see this experiment).

Test some of your tap water by pouring a small amount of indicator (3-4mm) into a glass and adding tap water.  If the solution is bluey purple then you have hard slightly alkaline water, if it is pink then you have slightly acidic water.  We want the water to start off slightly alkaline, so add a little bicarbonate of soda to your tap water until it stops testing pink.

Split your water into two, carbonate half of it, and leave the other half alone.

Now test both the carbonated and uncarbonated water with your red cabbage indicator and see if there is a difference.

What may happen

You should find that the carbonated water makes the water much more acidic than the straight tap water.

This is the reason why if you taste the carbonated water it has a tangy, sharp - acidic taste.

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