Page 30 - Big Ideas Year 10 sciPAD 2025

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30 SCIPAD - BIG IDEAS - BOOK 2
BASIS OF CHEMICAL REACTIONS
What is an Acid?
The word acid comes from the Latin ‘acidus’, meaning sour, and in everyday life people
will often describe something as being acidic when it has a sharp or sour taste. Acids
are a group of chemicals that are used widely, not only by scientists, but also by lots
of people in everyday life.
All acids contain hydrogen atoms, and will release hydrogen ions (H+) when they
dissolve in water.
Some acids are very dangerous and can corrode (or ‘eat away’) metals, paint and
even skin! Many acids, however, are considered weak acids and are safe enough to
eat or drink.
There are two main groups of acids - organic acids and mineral acids. Organic acids are made
by living things and examples can be found in oranges and lemons (citric acid), yoghurt (lactic
acid), grapes and tea (tartaric acid), and vinegar (acetic acid). Mineral acids are made from
inorganic substances, and are generally a lot stronger than organic acids. We commonly use
three mineral acids in the school laboratory - hydrochloric acid, nitric acid and sulfuric acid.
1. Where does the word ‘acid’ come from? 
2. Name the atom that all acids contain. 
3. Suggest what it means when we say an acid “corrodes a metal”? 

4. Name the two main groups of acids. 
5. Outline how each of the two main groups of acids are made.
(a) Organic acids are made by 
(b) Mineral acids are made from 
6. Name three acids we often use in the school laboratory.
(a) 
(b) 
(c) 
7. Explain the main difference between a concentrated acid and a dilute acid. 




Concentrated acids contain a
large amount of ‘acid particles’.
Dilute acids contain a small
amount of ‘acid particles’.
Hydrogen
ions (H+)
Remember an ‘ion’ is a charged
particle because it has lost or
gained electrons.
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