Class 10 Acids, Bases and Salts: learn it with free online activities

For students · Updated 2026-11-10 · For Class 10

Indicators, the pH scale, neutralisation and everyday salts for Class 10, with four free activities, safe kitchen experiments and quick self-check questions.

Acids taste sour, bases feel soapy, and when the two meet they cancel each other out and make a salt and water. That one idea runs through the whole chapter on acids, bases and salts. This article shows you which free activity to open for each part, how to get the most from them, and a safe experiment you can do in the kitchen. Start with the pH scale explorer, then watch neutralisation happen in the titration curve simulator.

What you will learn

• Indicators: substances that change colour in acids and bases, such as litmus, phenolphthalein, methyl orange and turmeric.
• The pH scale: a number from 0 to 14. Below 7 is acidic, 7 is neutral, above 7 is basic. Each step down means ten times more hydrogen ions.
• Neutralisation: an acid and a base reacting to give a salt and water.
• Salts you meet every day: common salt, baking soda, washing soda, bleaching powder and plaster of Paris, and how some are made from common salt.
• Water of crystallisation: water locked inside crystals, like the five water molecules in blue copper sulfate.

Which activity to use when

The titration tool goes beyond Class 10. Keep to the simple strong acid and strong base choice, and look only at the shape of the curve and where the jump happens.

How to use them properly

1. Predict first. Before you tap soap, say out loud whether its pH is above or below 7. A wrong guess teaches you more than no guess.
2. Say why. After each result, explain it in one sentence: “Soap is basic, so phenolphthalein turns pink.”
3. Keep units. Masses in grams, volumes in millilitres, concentrations in mol/L. A number without a unit is only half an answer.
4. Check answers. In the crystallisation activity, the working is shown step by step. Do the sum yourself first, then compare.
5. Use Check yourself. The pH explorer ends with practice questions, and New questions gives a fresh set.

Try this at home (safe)

Make your own indicator from red cabbage. Ask an adult to help with the knife and the warm water. Do not taste anything you test, and wash your hands afterwards.

1. Chop a few red cabbage leaves and soak them in warm water for 15 minutes.
2. Strain the purple liquid into a clear glass jar. This is your indicator.
3. Pour a little into three small cups.
4. Add a spoonful of lemon juice to the first, plain water to the second and a pinch of baking soda to the third.
5. Write down the colours: lemon turns it pinkish red, water stays purple, baking soda turns it blue-green.

Now open the pH explorer and find lemon juice and baking soda on the scale. Do your colours match the side of 7 each one sits on? Only use kitchen substances. Never use bathroom cleaners, drain cleaner or any acid from a shop at home.

Check yourself

1. Solution A has pH 3 and solution B has pH 5. Which has more hydrogen ions, and how many times more? A. Each step is ten times, and there are two steps, so A has 10 × 10 = 100 times more.

2. A student adds dilute base to an acid with phenolphthalein in it. When does it turn pink? When all the acid has been neutralised and a tiny extra drop of base makes the solution basic.

3. 2.50 g of blue copper sulfate is heated to constant mass and 1.60 g of white powder is left. Find x in CuSO₄·xH₂O. Water lost = 2.50 g − 1.60 g = 0.90 g. Moles of water = 0.90 ÷ 18.02 ≈ 0.050. Moles of CuSO₄ = 1.60 ÷ 159.6 ≈ 0.010. x = 0.050 ÷ 0.010 = 5. Check it in the crystallisation water activity with your own three weighings.