Materials and Change
5th Class
In fifth class the pupils were learning about pH scales.
The pH scale is a number scale from 0 to 14. It tells us how acidic or alkaline a solution is. The pH scale is used to classify solutions as acidic, alkaline or neutral.
- Neutral solutions are exactly pH 7.
- Acidic solutions have pH values less than 7. The closer to pH 0, the more acidic a solution is.
- Alkaline solutions have pH values more than 7. The closer to pH 14, the more alkaline a solution is.
Making an indicator
Lots of highly coloured vegetables and flowers can be used to make indicators just by mashing them in hot water. Red cabbage is one of the best, and can be compared to the coloured pH scale.
Pupils in 5th class used the following to make their own indicator.
- Red cabbage
- Boiled water
- Household substances to test, such as lemon water, pure water, salted water, dissolved vitamin c tablet,soda with lime and honey.
First the pupils prepared the cabbage water.
- Chopped up the red cabbage into small pieces and placed it in a mug.
- Added freshly boiled water from the kettle.
- Stirred the cabbage and boiled water until a deep purple solution was made
They put 20ml of each of the solutions in separate bottles. Next they added 50ml of the red cabbage water to each of the bottles.
The pupils observed how the colours changed in each bottle.
They compared it to the pH indicator to get a final result.
The results were as follows:
Water-pH 7(neutral)
Salted water pH 7 (neutral)
Honey -pH 4 (acidic)
Soda with lime pH 3 (acidic)
Lemon water -pH3 (acidic)
Dissolved vitamin c tablet -pH 2(acidic)
This experiment helped 5th class better understand how the pH scale is used to measure acidity and alkalinity, and how common household substances can vary widely in their pH levels.They thoroughly enjoyed this lesson on chemistry.
