GCSE Chemistry Acids, Bases and Salts Worksheet - Free Printable

Here are the answers to your homework questions, explained simply.

Q9. State true or false.
Excessive use of fertilisers in the soil makes the soil basic.
Answer: False
*(Reasoning: Most chemical fertilizers are acidic. Using them too much usually makes the soil acidic, not basic.)*

Q10. State true or false.
Phenolphthalein and methyl orange are examples of indicators.
Answer: True

Q11. Why are antacids used to cure acidity?
Our stomach produces acid to help digest food. Sometimes, it produces too much acid, which causes pain (acidity). Antacids are mild bases (alkalis). When you take an antacid, it mixes with the extra acid in your stomach and neutralizes it, stopping the pain.

Q12. Name any two antacids.
1. Milk of Magnesia (Magnesium hydroxide)
2. Sodium bicarbonate (Baking soda)

Q13. Why do we use calamine solution on ant bites?
When an ant bites, it injects a liquid called formic acid into the skin, which causes burning and itching. Calamine solution is a mild base. When applied to the bite, it neutralizes the acid effect of the sting and gives relief.

Q14. Why is factory waste neutralised before disposing of?
Factory waste often contains strong acids. If this waste is thrown directly into rivers or lakes, the acid can kill fish and other aquatic animals and pollute the water. Therefore, factories treat the waste with basic substances to neutralize the acid before throwing it away.

Q15. What is the chemical name of milk of magnesia?
Magnesium hydroxide.

Q16. What is an indicator?
An indicator is a special substance that changes color when mixed with an acid or a base. This color change tells us whether a solution is acidic, basic, or neutral. Examples include litmus paper and turmeric.

Q17. What is a universal indicator?
A universal indicator is a mixture of several different indicators. Unlike simple indicators that might just turn red or blue, a universal indicator shows many different colors for different pH values. It helps us find out exactly how strong an acid or base is.

Q18. What is a pH scale?
The pH scale is a measuring tool used to determine how acidic or basic a substance is. The scale usually runs from 0 to 14:
* 0–6: Acidic
* 7: Neutral (like pure water)
* 8–14: Basic

Q19. Differentiate between acid and base.

| Feature | Acid | Base |
| :--- | :--- | :--- |
| Taste | Sour (like lemon) | Bitter |
| Touch | Not soapy | Soapy and slippery |
| Litmus Test | Turns blue litmus red | Turns red litmus blue |
| Example | Vinegar, Lemon juice | Soap, Baking soda |

Q20. What is a neutralisation reaction? Explain it with the help of an example.
A neutralisation reaction happens when an acid and a base react with each other. They cancel out each other's effects to form two new things: a salt and water. Heat is also produced during this reaction.

Example:
Hydrochloric Acid (Acid) + Sodium Hydroxide (Base) → Sodium Chloride (Salt) + Water

$$HCl + NaOH \rightarrow NaCl + H_2O$$