Check important extra questions from CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure (with Answers). These Class 9th NCERT textbook based questions are very simple and can easily be attempted in less than 5 minutes if someone has understood the chapter well. These questions are also important for CBSE Class 9 Science exam 2020-21.
CBSE Class 9 Science: Extra Questions (Chapter 2: Is Matter Around Us Pure)
1. Shredding of paper is a ______ change.
(a) physical
(b) chemical
(c) physical and chemical
(d) natural
Answer: (a)
Shredding of paper is a physical change.
2. Regarding properties of colloid, which of the following is correct?
(a) A colloid is a heterogeneous mixture.
(b) The size of particles of a colloid is too small to be individually seen by naked eyes.
(c) Colloids are big enough to scatter a beam of light passing through it and make its path visible.
(d) All of these are correct.
Answer: (d)
Following are the properties of a colloid
• A colloid is a heterogeneous mixture.
• The size of particles of a colloid is too small to be individually seen by naked
eyes.
• Colloids are big enough to scatter a beam of light passing through it and make its path visible.
• They do not settle down when left undisturbed, that is, a colloid is quite stable.
CBSE Class 9 Revised Syllabus for 2020-2021
3. Which of the following statements about alloys are true?
(i) An alloy can be a mixtures of two or more metals
(ii) An alloy can be a mixture of a metal and a nonmetal
(iii) An alloy cannot be separated into their components by physical methods.
(iv) All the statements are true.
Answer: (iv)
Alloys are mixtures of two or more metals or a metal andanon-metal and cannot be separated into their components by physical methods. But still, an alloy is considered as a mixture because it shows the properties of its constituents and can have variable composition. For example, brass is a mixture of approximately 30% zinc and 70% copper.
4. Which of the following statements regarding properties of compounds are true?
(i) The composition of each new substance is always fixed.
(ii) The new substance has totally different properties.
(iii) The constituents can be separated only by chemical or electrochemical reactions.
(iv) All of the options are correct
Answer: (iv)
5. Which of the following is the major constituent of air in our atmosphere?
(i) Oxygen
(ii) Carbon dioxide
(iii) Nitrogen
(iv) Helium
Answer: (iii)
Air is a homogeneous mixture of a number of gases. Its two main constituents are:
oxygen (21%) and nitrogen (78%). The other gases are present in very small quantities.
6. Mass by mass percentage of a solution = ________
(a) [(mass of solute)/(mass of solution)] x 100
(b) [(mass of solute)/(volume of solution)] x 100
(c) [(volume of solute)/(volume of solution)] x 100
(d) [(mass of solution)/(mass of solute)] x 100
Answer: (a)
Mass by mass percentage of a solution = [(mass of solute)/(mass of solution)] x 100
7. Fog is a common example of colloids in which ______
(a) dispersed phase is liquid & dispersing medium is gas
(b) dispersed phase is solid & dispersing medium is gas
(c) dispersed phase is gas & dispersing medium is liquid
(d) dispersed phase is liquid & dispersing medium is liquid
Answer: (a)
In case of Fog, dispersed phase is liquid & dispersing medium is gas.
8. Which kind of colloid is cheese?
(a) Aerosol
(b) Foam
(c) Gel
(d) Solid sol
Answer: (c)
Jelly, cheese, butter are Gel type Colloids (Dispersed Phase: Liquid & Dispersing Medium: Solid).
9. A suspension is a ________
(a) homogenous mixture
(b) heterogeneous mixture
(c) pure substance
(d) compound
Answer: (b) heterogeneous mixture
Materials that are insoluble in a solvent and have particles that are visible to naked eyes, form a suspension. A suspension is a heterogeneous mixture.
10. Light is scattered by the particles of dust and smoke in the air, this phenomenon is known as ___________
(a) Reflection
(b) Refraction
(c) Suspension
(d) Tyndall effect
Answer: (d) Tyndall effect.
