Q1.
Does everything you put in water disappear?
Answer
No. Activity 6.7 answers this directly — only some materials disappear.
- Soluble materials disappear: sugar, salt, glucose, ORS powder, gur (jaggery), alum. They dissolve and the water stays clear.
- Insoluble materials do not disappear: sand and chalk powder settle at the bottom; sawdust and small pieces of wood float on top; mustard oil forms a separate layer.
How to be sure it has really dissolved: hold the glass up to the light after a few minutes of standing. If no particle can be seen anywhere — not floating, not settled — the material has dissolved. If anything is visible, it is insoluble.
Make your own ORS! ORS — Oral Rehydration Solution — is used to treat dehydration caused by diarrhoea. Ready packets are available at primary health centres; each is dissolved in one litre of water. If a packet is not available, mix six teaspoons of sugar and half a teaspoon of common salt in one litre of boiled and cooled water. It works only because sugar and salt are soluble.