Sorting Materials into Groups — Important Questions

Insoluble

Step 1: When a substance does not dissolve in water, we call it insoluble. Step 2: If you add sand to water and stir it, the sand particles do not disappear. Step 3: After some time, the sand settles down at the bottom of the glass — this is a clear sign that it is insoluble. Step 4: Salt and sugar are soluble because they disappear in water, but sand stays as separate particles. So, sand is insoluble in water.

Soft material

Step 1: Materials can be grouped as hard or soft based on how easily they can be compressed or scratched. Step 2: Soft materials are those that can be compressed or squeezed easily. Step 3: Cotton is very easy to compress and squish — you can press it easily with your fingers. Step 4: In contrast, iron is a hard material because it cannot be easily compressed or scratched. Cotton is therefore a soft material.

Buyers can easily see the biscuits inside

Step 1: Transparent materials allow us to see clearly through them. Step 2: When biscuits are kept in a transparent glass or plastic container, customers can see the biscuits without opening the container. Step 3: This helps buyers easily identify what is inside and choose what they want. Step 4: This is a practical use of the property of transparency in everyday life — it is convenient for both the shopkeeper and the customer. So, the reason is that buyers can easily see the biscuits inside.

Oil forms a separate layer on water

Step 1: Some liquids mix with water (like vinegar and lemon juice) while some do not. Step 2: Oil does not dissolve in water because it is not soluble in water. Step 3: Since oil is lighter than water (less dense), it floats on top and forms a separate layer. Step 4: You might have seen this at home — when cooking oil falls into water, it does not mix but floats on top as a separate layer. This is exactly what happens here.