Archimedes is well known for discovering that when you enter into a bath, the water level immediately rises. He noticed that the weight of his body displaced a certain amount of water. However, when you add salt into water, the level actually decreases, as the dissolving ions in the water allow the solvent molecules to get closer together!! There are many interesting facts about salt. For example, it is often added to food as a preservative. This is due to the fact that it will draw out water from the food by osmosis, and prevent bacteria growing and spoiling the food.
However, if you are more interested in language than science, salt crops up all the time in common phrases.
“Take it with a grain of salt”. This saying actually originated in ancient Rome, as they believed salt protected people from poison. It is often used nowadays when someone doubts what they hear.
“Salt of the earth”. This one comes from the Bible, and is used to describe a lovely person.
“Rub salt in the wound” If you have ever tried rubbing salt in a wound, you will know it is painful! It is used when someone is making a bad situation even worse.
For GCSE Science – you need to be able to explain how you would make soluble salts. It is one of the required practicals you must revise.
Making Salts, Electrolysis and Temperature Changes.
You will find a brief description of what you need to know about each practical, and key questions you may be asked. As always there are questions to try, and answers to check your understanding.
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