Olympiad Science - Separation of Substances
Exam Duration: 45 Mins Total Questions : 30
'X' is a separation technique based on the difference in weights of the solids in a solid-solid mixture. What is 'X'?
- (a)
Sieving
- (b)
Handpicking
- (c)
Threshing
- (d)
Winnowing
'X' is winnowing, a process which uses the difference in weights of solids in a solid-solid mixture for separating the components.
What type of a substance is steel?
- (a)
A solid-liquid heterogeneous mixture
- (b)
A solid - solid heterogeneous mixture
- (c)
A solid - solid homogeneous mixture
- (d)
A pure substance
Steel is uniform in its composition. Hence, it is a homogeneous mixture of solids.
flow chart which gives the techniques a student adopted to separate the constituents of a mixture.
What could the mixture be?
- (a)
Water + sand + glass
- (b)
Oxygen + hydrogen + salt
- (c)
Stones + rice + water
- (d)
Chalk powder + sugar + water
It is a mixture of chalk powder, sugar and water. The chalk powder gets separated from sugar water by filtration. Later, sugar from sugar water is separated by distillation.
flow chart which gives the techniques a student adopted to separate the constituents of a mixture.
What is substance Q?
- (a)
Sugar
- (b)
Chalk powder
- (c)
Alcohol
- (d)
Oxygen
Q should be a substance that is solid and insoluble in water i.e., chalk powder.
Identi y the compound from the following
- (a)
Oxygen
- (b)
Carbon dioxide
- (c)
Hydrogen
- (d)
Air
A compound is a substance which contains only one type of molecules i.e.CO2 .
Identify the element from the following.
- (a)
Oxygen
- (b)
Carbon dioxide
- (c)
Water
- (d)
Air
An element is a substance which is made up of only one type of atoms. Oxygen (O2) is diatomic in nature.
Which of the following is an example of a solid-in-gas mixture?
- (a)
Soil
- (b)
Smoke
- (c)
Moisture
- (d)
Dew
Minute solid particles float along with vapours (fumes) in the smoke. Hence, smoke is a solid-in-gas mixture
Which of the following does NOT belong to the group formed by the others?
- (a)
Brass
- (b)
Water
- (c)
Butter-milk
- (d)
Steel
Water is a pure substance and all others are solid-in-solid and solid-in-liquid mixtures.
In a mixture, constituents exhibit
- (a)
similar properties.
- (b)
only those properties which are characteristic to the mixture.
- (c)
their own properties.
- (d)
no properties.
The components of a mixture are not chemically bound. Therefore, they retain their individual properties.
What is the process by which a gas changes into a liquid?
- (a)
Decantation
- (b)
Sublimation
- (c)
Condensation
- (d)
Sedimentation
When a gas changes into a liquid, the process is known as condensation.
What kind of mixtures are alloys?
- (a)
Solid-Gas
- (b)
Liquid-Liquid
- (c)
Gas-Gas
- (d)
Solid-Solid
A mixture of solid-in-solid is called an alloy
Identify the liquid-in-gas type of mixture from the following.
- (a)
Dissolved carbon dioxide in water
- (b)
Droplets of water in air
- (c)
Dissolved oxygen in water
- (d)
All of the above
Droplets of water in air form a liquid-in-gas type of mixture.
A homogeneous mixture
- (a)
is made up of one type of molecules.
- (b)
is the one in which the components can be distinguished.
- (c)
is the one in which the components cannot be distinguished.
- (d)
can be separated into its constituents physically .
A homogeneous mixture is the one in which the components cannot be distinguished because they are completely mixed together and are in one phase
A mixture contains three different substances X, Y and Z. They are of the same size, cubical in shape and yellow in colour.X particles are very heavy, insoluble, nonmagnetic and contribute 50%ofthe mixture. Y particles are very light, insoluble, nonmagnetic and contribute40% of the mixture. And Z particles are iron pieces. Which of the following methods can separate X, Y and Z?
- (a)
Winnowing, Magnetic separation
- (b)
Magnetic separation, Winnowing
- (c)
Sieving, Magnetic separation, Filtration
- (d)
Handpicking, Sublimation, Sieving
Very light particles Y can be separated by winnowing, while 'Z' being magnetic in nature, can be separated by magnetic separation leaving behind 'X'.
'X' is a separation technique used only when the components of a solid-solid mixture have different sizes. Identify 'X:
- (a)
Winnowing
- (b)
Sieving
- (c)
Threshing
- (d)
Magnetic separation
Sieving is a separation technique used only when the components of a solid-solid mixture have different sizes
Given below are some methods of separation.
x - Winnowing
Y - Threshing
Z - Sieving
Which of the following methods of separation does not require air for the process of separation?
- (a)
Only X
- (b)
Only Y, Z
- (c)
Only Z, X
- (d)
X, Y and Z
Only winnowing (X) needs air for the process of separation. While threshing (Y) and sieving (Z) do not need air while they are carried out.
How is scrap-iron separated from other wastes in the scrap yard?
- (a)
Sublimation
- (b)
Magnetic separation
- (c)
Handpicking
- (d)
Winnowing
Iron has the tendency to get attracted by magnets. Hence, by using magnets, scrap iron can be separated from other wastes.
Which of the following are involved in filtration technique?
- (a)
Hair in our nostrils
- (b)
Oil and air filters in cars
- (c)
Air filters in air conditioners
- (d)
All of the above
In all the cases, dust is filtered out from the air by using filtration method.
What process is used for separating heterogeneous mixtures of insoluble solid-in-liquid?
- (a)
Filtration
- (b)
Crystallization
- (c)
Sublimation
- (d)
Fractional distillation
In heterogeneous mixtures the components can be differentiated. Hence, the solid particles are separated from liquid by using filtration method.
Study the information given below.
1. Some substances are made up of two or more elements combined together chemically
2. Properties of these substances are different from the elements that make them
3. This substance cannot be broken down by physical methods.
Which of the following substances has the properties listed above?
- (a)
Iodine
- (b)
Calcium
- (c)
Air
- (d)
Sugar
The three given properties are those of compounds. In the given options, sugar is a compound
The flow chart given below are examples of materials X and Y.
Identify X and Y.
- (a)
x y Non metals Metals - (b)
x y Mixtures Metals - (c)
x y Compounds Elements - (d)
x y Compounds Pure substances
Air, liquor ammonia and milk are mixtures while copper, aluminium and iron are metals which are pure substances.
A glass filled with ice cubes is kept on a table. After sometime water drops were observed sticking to the outside of the glass. Which of these sentences is TRUE of this phenomenon?
(i) This phenomenon is known as condensation.
(ii) This proves that water vapour is present in air.
(iii) This is also observed when a hot object is cooled in the open.
- (a)
Only (i) and (ii)
- (b)
Only (ii) and (iii)
- (c)
Only (i) and (iii)
- (d)
(i), (ii) and (iii)
Statements (i) and (ii) are true of the given phenomenon.
Butter can be separated from milk or curd by
- (a)
mixing.
- (b)
churning
- (c)
using a juicer
- (d)
all of these.
Churning will separate the light butter from the rest of the milk or curd. Butter will float on top.
If there are some stones mixed with rice grains, we can remove these stones by
- (a)
threshing.
- (b)
winnowing
- (c)
adding water and then decantation.
- (d)
handpicking.
Stone pieces can be easily removed by handpicking. The density of grains of rice and that of stones may be similar so they cannot be separated by winnowing or decantation. Both one denser than water and sink in water. Threshing is a process of separating grains from stalks and involves beating of stalks to free the grains.
There is a lot of husk in wheat grains. Which method should be used to separate the grains?
- (a)
sieving
- (b)
handpicking
- (c)
threshing
- (d)
winnowing
Winnowing separates heavier and lighter components of a mixture using wind. Lighter husk will be carried away by wind. Sieving is used to separate components of different sizes.
Filtration is done when
- (a)
we remove tea leaves from tea.
- (b)
we make cottage cheese or paneer.
- (c)
we need to purify water
- (d)
all of these.
Different mixtures will need filters of different pore sizes. A tea strainer is a filter of large pore size. Cotton cloth is used for filtering solid cottage cheese from the liquid. Cotton cloth has smaller pore size than a tea strainer. For water purification we need still smaller pore size.
Pulkit added five spoons of salt to a glass of water. The salt dissolved when the water was stirred well. He added another spoon of salt but the salt sank to the bottom and did not dissolve even on stirring. This is because
- (a)
the salt solution is saturated.
- (b)
water cannot dissolve any more salt in it.
- (c)
the last spoon of salt had a different salt.
- (d)
both 'a' and 'b'.
A solution becomes saturated if it cannot dissolve any more of the substance in it. More salt can be dissolved in the same amount of water if the solution is heated but if this solution cools down the excess salt will appear at the bottom again. Also, water dissolves different soluble substances in different amounts.
Shalu found that there is too much ghee in a particular curry. To remove excess of ghee, she should
- (a)
put the curry in the fridge to cool.
- (b)
remove ghee from top with the help of a ladle.
- (c)
put the curry in the fridge to cool and then remove ghee from top with the help of a ladle.
- (d)
none of these
Ghee solidifies easily on cooling. It can then be easily removed with the help of a ladle.
Select the right match
Column I | Column II |
i) chalk powder and water | A) handpicking |
ii) oil and water | B) separating funnel |
iii) rice and peas from cooked pulao | C) sedimentation and decantation |
- (a)
i-C; ii-B; iii-A
- (b)
i-B; ii-A; iii-C
- (c)
i-A; ii-C; iii-B
- (d)
i-B; ii-C; iii-A
Chalk powder can be allowed to settle down. The water can then be decanted as chalk is insoluble in water. Oil and water can be separated by using a separating funnel. Children can be seen picking out peas from peas pulao.
There is a lot of air pollution and there is a high increase in particulate matter in the air of Delhi. Every day we see a layer of dust on the furniture. This is due to the fact that
- (a)
dusting is not a priority with us.
- (b)
dust gets removed from air.
- (c)
air is not circulating properly.
- (d)
particulate matter like dust is heavier and tends to settle down due to gravity
Air contains a lot of suspended dust particles. With time and gravity they settle on all available surface.