Class 7 Science: Acids, Bases and Salts

The label acid or base describes how a substance behaves in a test, not whether it is automatically dangerous or useful.

What to understand

Describe the central idea in your own words.
Use a model, observation or relationship to explain a changed example.
Notice and correct the likely misconception in the worked reasoning.

Evidence from indicators

Indicators provide evidence: a colour change helps classify a solution. Acids and bases can react in neutralisation; the products are commonly described as salt and water, though the exact salt depends on the substances involved.

The same substance can be appropriate in one context and harmful in another. Never taste or mix household chemicals to test a claim; use teacher-approved materials and procedures.

Worked reasoning: If an indicator changes colour in lemon juice but not in sugar solution, the observation supports different chemical behaviour. It does not prove that every sour substance is equally acidic or that colour alone gives a precise strength.

Try, explain and check

Reasoning

Why is an indicator more useful than taste?

Show a reasoning prompt

State the evidence, relationship or model that supports your answer, then check whether the units and direction make sense.

Application

Explain why an antacid can reduce discomfort caused by excess stomach acid.

Show a reasoning prompt

State the evidence, relationship or model that supports your answer, then check whether the units and direction make sense.

Misconception

Neutral means near-neutral behaviour in the test; it does not mean “nothing is present.”

Show a reasoning prompt

State the evidence, relationship or model that supports your answer, then check whether the units and direction make sense.

Next step

Write a three-sentence revision summary, then continue to the related resource. For extra practice, visit the resource library and choose a worksheet that matches the skill you need.

About this resource
Prepared as part of the BIS Quiz learning resource. It is supplementary study material; use your teacher's instructions and prescribed materials when they differ. Report a factual error or unclear explanation.