Matter in Our Surroundings and Its Purity (Class 9)

What this worksheet covers

This is an eighteen-question practice worksheet on matter in our surroundings and its purity for Class 9, written to the pattern of the SOF National Science Olympiad (NSO). It carries 24 marks and is designed to be attempted in 45 minutes, split across three sections — Scientific Reasoning, Applying What You Know and Achievers Section. Every question is multiple choice with exactly one correct option, and every one comes with a fully worked solution rather than just an answer key — so a child who gets one wrong can see where the reasoning went astray instead of only learning that it did.

Skills your child practises

• Applied problem-solving on matter in our surroundings and its purity at Class 9 level
• Working accurately against a time limit, as the real paper demands
• Scientific Reasoning questions in the olympiad format
• Applying What You Know questions in the olympiad format
• Achievers Section questions in the olympiad format
• Reading worked solutions to find the step that went wrong

How to use it

1. 1There are 18 questions in this worksheet. All questions are compulsory.
2. 2Each question has four options (A), (B), (C) and (D). Exactly one option is correct.
3. 3Questions 1–15 carry 1 mark each. Questions 16–18 (Achievers Section) carry 3 marks each.
4. 4There is no negative marking. Study every diagram and table carefully.

Sample questions from this worksheet

A preview of what's inside Matter in Our Surroundings and Its Purity (Class 9) — the PDF has the full set, and every question comes with a worked solution like these.

1. 1. Which state of matter has a definite volume but no definite shape?

   • ASolid
   • BPlasma
   • CGas
   • DLiquidcorrect
   Solution: A liquid keeps its volume because its particles stay close together, but it flows and takes the shape of its container because those particles can slide past one another. A solid holds both shape and volume; a gas holds neither.

2. 2. A mixture contains common salt, sand and ammonium chloride. Which step should be carried out first to separate them?

   • AHeat the mixture so that one component sublimescorrect
   • BAdd water and filter
   • CDistil the mixture
   • DUse a magnet
   Solution: Ammonium chloride sublimes on heating, so warming the mixture removes it first as a vapour that resolidifies on a cool surface. The remaining salt and sand are then separated by dissolving in water, filtering off the sand, and evaporating the filtrate.

3. 3. Assertion (A): A desert cooler cools better on a hot, dry day than on a humid day.Reason (R): The rate of evaporation increases when the humidity of the surrounding air is low.

   • ABoth A and R are true and R is the correct explanation of Acorrect
   • BBoth A and R are true but R is not the correct explanation of A
   • CA is true but R is false
   • DA is false but R is true
   Solution: Dry air can accept much more water vapour, so evaporation from the cooler’s wet pads is fast, and fast evaporation removes more heat from the air being blown through. Both statements are true, and the low humidity is exactly why the cooler works better, so R correctly explains A.