Hoshi's kitchen is full of acids and bases — and he had no idea. The lemon? Acid. The baking soda? Base. The salt in his food? Formed when an acid met a base. This post explains what acids, bases, and salts actually are — simply, clearly, with examples you already know.
An acid is a substance that tastes sour and turns blue litmus paper red.
Think of the sharpest flavour you know — lemon, tamarind, vinegar. That sourness is caused by acids present in those substances.
A base is a substance that tastes bitter, feels soapy or slippery, and turns red litmus paper blue.
Bases are the opposite of acids. The bitterness of bitter gourd (karela), the feel of soap between your fingers, the slippery texture of baking soda solution — all of these are properties of bases. Want to see how acids and bases compare side by side? Check out our post on the difference between acids and bases.
A salt is a substance formed when an acid reacts with a base. This reaction is called neutralisation. The most familiar salt is common table salt — sodium chloride (NaCl). It forms when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH).
We use indicators to identify acids and bases safely — without tasting unknown substances. Litmus, turmeric, and china rose are the most common indicators used in Class 7 science. We have a detailed post on how these indicators work — worth reading after this.
Now that you understand what acids, bases, and salts are, the next step is to go through the complete Class 7 notes on acids, bases, and salts — they cover everything you need for your exam in one place. You can also practise with the important questions on acids, bases, and salts to test how much you have understood.
An acid is a substance that tastes sour and turns blue litmus paper red. Examples: lemon juice (citric acid), vinegar (acetic acid), tamarind (tartaric acid), curd (lactic acid), ant sting (formic acid).
A base is a substance that tastes bitter, feels soapy or slippery, and turns red litmus paper blue. Examples: baking soda (sodium bicarbonate), soap, lime water (calcium hydroxide), washing soda (sodium carbonate).
A salt is a substance formed when an acid reacts with a base in a neutralisation reaction. The most common example is common table salt — sodium chloride (NaCl).
Lemon juice is an acid. It contains citric acid, which gives it its sour taste. If you test lemon juice with blue litmus paper, it turns red — confirming it is acidic. Learn more about how litmus and other indicators work in our post on indicators in science.
Baking soda (sodium bicarbonate) is a base. It tastes slightly bitter, feels slightly soapy, and turns red litmus paper blue. It is commonly used to neutralise acids.