I know, I know, I shouldn’t call in Fun Friday when I am posting it on a Saturday, but ignoring the fact that I am a day late with this regular blog post, I hope you enjoy!
Exploring Acids and Bases
What are Acids and Bases?
Acids and Bases are chemicals that occur naturally in lots of different substances.
Acids can be found in things like lemons and vinegar; Bases (also called Alkali) are found in toothpaste or many cleaning products. Bread soda is a base.
Lets learn more!
The Bronsted-Lowry Definition of an acid and a base is…
- Acids are substances that gives up hydrogen ions (H+).
- Bases are substances that accept hydrogen ions (H+).
- These hydrogen (H+) ions can change things in many ways, including taste and colour!
Did you know… that the word acid comes from the Latin word acidus meaning sour!
Lemons contain an acid called
citric acid that gives them that
sour taste!
The pH Scale
The pH scale is a scale that measures how acidic or basic a substance is.
The pH scale goes from 0 to 14. The scale for acids goes from 0 to 7. A very strong acid has a pH of 0. The scale for bases goes from 7 to 14. A very strong base has a pH of 14.
Something with a pH of 7 is said to be neutral (neither an acid or a base). Pure water has a pH of 7.
“Did you know… that bee sting venom contains an acid called formic acid!”
Acids and bases in plants!
An indicator is something that can determine whether a substance is an acid or a base. Many indicators are natural chemicals.
A group of chemicals called anthocyanins are naturally present in a number of different plants such as apples, grapes, the leaves of many trees and flowers such as roses and poppies.
The colour of anthocyanin changes depending upon the acid levels (pH) of the plant. The bright red and pink colours of Autumn are due to anthocyanin and acid levels in leaves (for more on this see my previous
post “Carrots, Cabbages and Cups of Tea“).
Anthocyanin changes colour from red to pink, to purple, to blue, to green as the pH changes from 0 to 14.
“Did you know… Hydrangea flowers can change colour depending on the pH of the soil. In acidic soils chemical reactions occur to make aluminium available to the plant, turning the flowers blue, in alkaline (basic) soil these chemical reactions cannot occur so the flowers remain pink.”
Experiments to try at home:
Make your own sherbet
You will need… icing sugar, citric acid, bread soda, flavoured jelly crystals, a teaspoon, a tablespoon and a mixing bowl.
What to do… add one teaspoon of citric acid and one teaspoon of bread soda to the bowl. Add three tablespoons of icing sugar and two tablespoons of flavoured jelly crystals. Mix all together then place a small amount on your tongue! The sherbet should bubble a little and you should feel a tingle on your tongue!
So what is happening?… you have just created an acid-base reaction in your mouth! When the citric acid, bread soda and saliva in your mouth combine they react together to give off a gas, called carbon dioxide, that forms tiny bubbles that you feel fizzing on your tongue!
Cabbage juice experiment
You will need… a red (purple) cabbage, a knife, a saucepan, a sieve, an ice tray, clear vinegar, water and bread soda
What to do… cut up half the red cabbage and add it to a pan. Ask and adult to cover with water and bring it to the boil then leave to cool. Once cool pour the cabbage juice through a sieve, collecting the juice in a bowl. Pour the juice into an ice tray and freeze until it hardens into ice-cubes.
Half fill three glasses, one with water, one with clear vinegar and one with water mixed with half a teaspoon of bread soda. Now drop a cabbage juice ice-cube into each glass and see what happens.
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| Cabbage Juice ice cube experiment |
So what is happening?… red cabbage contains anthocyanin. When the cabbage juice mixes with the acid (vinegar) it turns a red/pink colour; when it mixes with the bread soda solution (base) it turns a blue/green colour. The water is neutral (pH 7) so it does not alter the purple colour of the cabbage juice.
