Acids and Alkalis


The Big Idea – Chemical reactions involve rearrangement of atoms in substances to form new substances.

In this topic we look at how acids and alkali react with different substances and with each other. Once we understand the basics we can see how we use this reaction in everyday life from treating Bee and Wasp stings to treating indigestion and why we use soap and toothpaste.

The Essentials

100 % Acids & Alkalis

Most acids and alkalis are clear liquids that look like water so we have to use indicators to check which is which. Universal indicator is very useful as it will tell us if a liquid is an acid, alkali or water and tell us how strong it is.

The reaction between an acid and an alkali is called a NEUTRALISATION reaction. You MUST know all about this reaction as it is a very important reaction in Chemistry.

You will often hear the term BASE in this topic. This is another word for alkali and they often get mixed up. A base is an alkali that does not dissolve in water. For now you can just treat alkali and base as being the same thing.

Acid + Alkali –> Salt + Water

Deeper Understanding

When we reach GCSE level we will understand a lot more about chemical formula. This then explains why any acid that reacts with any alkali always makes water.

All acids contain H

All alkalis contain OH

When we combine them together (as in the Big Idea) we make H2O (2H’s and 1 O) – Water!

Other Links

BBC Bitesize – Acids

Review and Rate your Understanding

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Let us know how you feel about this topic in the comments section below. Any questions you have, just ask.

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