Answer in one or two words only
1) Name one property of a compound that changes if it has impurities in it, and can be used to test the purity of the compound.
2) Can a mixture of sawdust and water be separated by sedimentation will take a long time. Name one method which can be used to speed up the process.
3) If insoluble particles of a solid in a liquid are very fine, sedimentation will take a long time. Name one method which can be used to speed up the process.
4) Give suitable methods used to separate a mixture of sand, salt and water.
5) Which of the mixture-water and oil, or water and alcohol can be separated by using a separating funnel?
6) Which method will you use to get pure water from tap water, for performing scientific experiments?
Answer in one sentence only
1) What principle is used in the separation of mixtures?
2) In a sieve, what should the size of the pores depend upon?
3) Which property is used to separate a mixture of two solids by winnowing?
4) Which property of filter paper is used to separate fine particles of an insoluble solid from a liquid?
5) What is loading?
6) Under which condition can handpicking be used to separate the constituents of a mixture.
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Answers
Question 1:
Most of the substances we see around us are
(a) pure elements.
(b) pure compounds.
(c) impure elements.
(d) mixtures.
ANSWER:
(d) mixtures
Most of the substances we see around us are mixtures of different elements and compounds.
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Question 2:
A solution of salt in water is a
(a) compound.
(b) homogeneous mixture.
(c) heterogeneous mixture.
(d) element.
ANSWER:
(b) homogeneous mixture
When salt is dissolved in water, the salt is distributed uniformly in the solution. Thus, the salt solution is a homogeneous mixture.
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Question 3:
The property used in separating a mixture of two solids by winnowing is
(a) difference in colour.
(b) difference in size.
(c) difference in weight.
(d) attraction by magnet.
ANSWER:
(c) difference in weight
Winnowing is used to separate two solids of different weights, such as wheat and chaff.
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Question 4:
The process of settling down of particles of a solid in a liquid is
(a) decantation.
(b) sublimation.
(c) sedimentation.
(d) filtration.
ANSWER:
(c) sedimentation
The process of settling down of particles of a solid in a liquid is known as sedimentation.
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Question 5:
Which method is used to obtain a pure liquid from a solution?
(a) distillation
(b) condensation
(c) filtration
(d) loading
ANSWER:
(a) distillation
Distillation can be used to obtain a pure liquid from a solution.
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Question 6:
The temperature of a saturated solution of sugar in water is raised by 10 °C. Which of these statements is now true?
(a) It will continue to be saturated.
(b) It will become unsaturated.
(c) Whether it remains saturated or becomes unsaturated depends on the amount of water taken.
(d) It will continue to be saturated, but if the temperature is increased beyond 10 °C it will become unsaturated.
ANSWER:
(b) it will become unsaturated
If the temperature of saturated sugar solution is increased by 10 oC, then more sugar can be dissolved in the solution and the solution becomes unsaturated.
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Question 7:
Which of the following can dissolve in water?
(a) only solids
(b) only solids and liquids
(c) solids, liquids and gases
(d) only liquids
ANSWER:
(c) solids, liquids and gases
Solids such as salt, liquids such as alcohol and gases such as nitrogen and oxygen can dissolve in water.
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Question 8:
Sedimentation and decantation are useful to separate
(a) immiscible liquids.
(b) soluble solid from liquid.
(c) insoluble solid from liquid.
(d) insoluble solid from a liquid where the solid is heavier than the liquid.
ANSWER:
(d) insoluble solid from a liquid where the solid is heavier than the liquid
Decantation and sedimentation can be used to separate solids from a liquid when the solid is heavier than the liquid and is insoluble in the liquid.
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Question 9:
A commonly used chemical for loading is
(a) hydrogen.
(b) alum.
(c) sulphur.
(d) common salt.
ANSWER:
(b) alum
Alum is a commonly used chemical for loading to speed up sedimentation.
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Question 10:
To get only the pure solid from its solution in water, which method will you use?
(a) evaporation
(b) distillation
(c) filtraction
(d) none of these
ANSWER:
(a) evaporation
Evaporation is the process used to get a pure solid from its solution in water.
Answer:
a Is homogenous mixture
Explanation:
b is homogenous mixture