Is Matter Around Us Pure
1. What is meant by substance?
Answer:
Substance is a pure form of matter.
2.List the points of differences -between homogeneous and heterogeneous mixtures.
Answer:
3. Differentiate between homogeneous and heterogeneous mixtures with examples.
Answer:
Answer:
4.How are sol, solution and suspension different from each other?
Answer:
5.To make a saturated solution, 36 g. of sodium chloride is dissolved in 100 g. of water at 293 K. Find its concentration at this temperature.
Answer:
6.How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25° C) which are miscible with each other?
Answer:
To separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), Fractional distillation method is used.
7.Name the technique to separate
1. butter from curd
2. salt from sea-water
3. camphor from salt.
Answer:
1. butter from curd: To separate butter from curd, centrifuge machine can be used or It can be separated by milk churner.
2. salt from seawater: To separate salt from the seawater evaporation method can be used.
3. Comphor from salt: By sublimation method, we can separate camphor from salt.
8.What type of mixtures are separated by the technique of crystallization?
Answer:
By crystallisation method, pure solid in the form of crystals can be separated.
9.Classify the following as chemical or physical changes:
1. cutting of trees
2. melting of butter in a pan
3. rusting of almirah
4. boiling of water to form steam
5. the passing of electric current through water and the water breaking down into hydrogen and oxygen gases
6. dissolving common salt in water.
7. making a fruit salad with raw fruits, and
8. burning of paper and wood.
Answer:
1. Cutting of trees: Physical change.
2. melting of butter in a pan: Physical change.
3. rusting of almirah: chemical change.
4. boiling of water to form steam: physical change.
5. passing of electric current, through water and the water breaking down into hydrogen and oxygen gases: chemical change.
6. dissolving common salt in water: physical change.
7. making a fruit salad with raw fruits: physical change.
8. burning of paper and wood: chemical change.
10.Try segregating the things around you as pure substances of mixtures.
Answer:
Answer:
To separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), Fractional distillation method is used.
7.Name the technique to separate
1. butter from curd
2. salt from sea-water
3. camphor from salt.
Answer:
1. butter from curd: To separate butter from curd, centrifuge machine can be used or It can be separated by milk churner.
2. salt from seawater: To separate salt from the seawater evaporation method can be used.
3. Comphor from salt: By sublimation method, we can separate camphor from salt.
8.What type of mixtures are separated by the technique of crystallization?
Answer:
By crystallisation method, pure solid in the form of crystals can be separated.
9.Classify the following as chemical or physical changes:
1. cutting of trees
2. melting of butter in a pan
3. rusting of almirah
4. boiling of water to form steam
5. the passing of electric current through water and the water breaking down into hydrogen and oxygen gases
6. dissolving common salt in water.
7. making a fruit salad with raw fruits, and
8. burning of paper and wood.
Answer:
1. Cutting of trees: Physical change.
2. melting of butter in a pan: Physical change.
3. rusting of almirah: chemical change.
4. boiling of water to form steam: physical change.
5. passing of electric current, through water and the water breaking down into hydrogen and oxygen gases: chemical change.
6. dissolving common salt in water: physical change.
7. making a fruit salad with raw fruits: physical change.
8. burning of paper and wood: chemical change.
10.Try segregating the things around you as pure substances of mixtures.
Answer:
1.Which separation techniques will you apply for the separation of the following?
a) Sodium Chloride from its solution in water.
b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
c) Small pieces of metal in the engine oil of a car.
d) Different pigments from an extract of flower petals.
e) Butter from curd.
f) Oil from water.
g) Tea leaves from tea.
h) Iron pins from sand.
i) Wheat grains from husk.
j) Fine mud particles suspended in water.
Answer:
a) Evaporation
b) sublimation
c) Filtration
d) Chromatography
e) Centrifuge.
f) By using separating funnel.
g) Filtration.
h) By using magnet
i) By siering
j) By Filtration.
2.Write the steps you would use for making tea. Use the words, solution, solvent, solute, dissolve, soluble, insoluble, filterate and residue.
Answer:
Steps for preparing tea:
1. Take water in a vesssel. Here water is solvent.
2. Add solutes like sugar and tea powder. Sugar dissolves tea powder is insoluble.
3. While boiling add milk to it.
4. By filtration, we get tea (filtrate) only leving behind tea powder as residue.
3.Pragya tested the solubility of three different substances at different temperatures and collected the data as a given below (results are given in the following table, as grams or substance dissolved in 100 grams of water to form a saturated solution)
a) Sodium Chloride from its solution in water.
b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
c) Small pieces of metal in the engine oil of a car.
d) Different pigments from an extract of flower petals.
e) Butter from curd.
f) Oil from water.
g) Tea leaves from tea.
h) Iron pins from sand.
i) Wheat grains from husk.
j) Fine mud particles suspended in water.
Answer:
a) Evaporation
b) sublimation
c) Filtration
d) Chromatography
e) Centrifuge.
f) By using separating funnel.
g) Filtration.
h) By using magnet
i) By siering
j) By Filtration.
2.Write the steps you would use for making tea. Use the words, solution, solvent, solute, dissolve, soluble, insoluble, filterate and residue.
Answer:
Steps for preparing tea:
1. Take water in a vesssel. Here water is solvent.
2. Add solutes like sugar and tea powder. Sugar dissolves tea powder is insoluble.
3. While boiling add milk to it.
4. By filtration, we get tea (filtrate) only leving behind tea powder as residue.
3.Pragya tested the solubility of three different substances at different temperatures and collected the data as a given below (results are given in the following table, as grams or substance dissolved in 100 grams of water to form a saturated solution)
(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
(c) Find the solubility of each salt at 393 K. Which salt has the highest solubility at this temperature?
(d) What is the effect of change of temperature on the solubility of a salt?
Answer:
(a) At temperature 313K to prepare 50 gms of potassium nitrate, we require 319 of potassium nitrate in 100 gms of water.
(b) Pragya observed that As a solution of potassium nitrate cools, it dissolves slowly.
(c)
1. At temperature 293 K, 32 gm of potassium nitrate dissolves.
2. At temperature 293K, the solubility of NaCl is 36 gm.
3. At temperature 293K, the solubility of KCl is 35 gm.
4. At temperature 293K, the solubility of NH4Cl is 37 gm.
(d) As temperature increases, rate of solubility increases.
4.Explain the following giving examples:
(a) Saturated solution.
(b) Pure Substance
(c) Colloid
(d) Suspension.
Answer:
(a) Saturated solution: At any particular temperature a solution that has dissolved as much solute as it is capable of dissolving is said to be a saturated solution.
(b) Pure substance: A pure substance consists of a single type of particles.
(c) Colloid: A colloid is a heterogeneous mixture whose size is too small to be individually seen by naked eyes.
(d) Suspension: A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye.
5.Classify each of the following as a homogenous or heterogeneous mixture of soda water, wood, air, soil, vinegar, filtered tea.
Answer:
Homogeneous mixture: soda water, air, vinegar, filtered tea, tree.
Heterogeneous mixture: soil.
6.How would you confirm that a colourless liquid given to you is pure water?
Answer:
Pure water is obtained by fractional distillation. It has only water molecules. By this, we conclude purity of water.
7.Which of the following materials fall in the category of a pure substance?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air
Answer:
Among these substances ice, iron, mercury, and tree are pure substances.
8.Identify the solutions among the following mixtures.
(a) Soil
(b) Seawater
(c) Air
(d) Coal
(e) Soda water
Answer:
(a) Soil: minerals.
(b) Seawater: salts
(c) Air: Nitrogen, Oxygen, and other gases.
(d) Coal: carbon
(e) Soda water: carbon dioxide.
9.Which of the following will show the ‘Tyndall effect’?
(a) salt solution
(b) milk
(c) copper sulphate solution
(d) starch solution
Answer:
Milk, copper sulphate, solution, and starch solution shows the ‘Tyndall effect’.
10.Classify the following into elements, compounds, and mixtures.
(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
(h) Coal
(i) Air
(j) Soap
(k) Methane
(l) Carbon dioxide
(m) Blood
Answer:
11.Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filling and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle
Answer:
Among these Rusting of iron, cooking of food, Burning of a candle are chemical changes.
Additional Questions and Answers
1.What is the special name of Alloy?
Answer :
Solid solution
2.Name the liquid metal.
Answer :
Mercury
3.What is a compound?
Answer :
A substance composed of two or more elements. Chemically combined with one another in a fixed proportion.
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