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What is meant by a pure substance?
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List the points of difference between homogeneous and heterogeneous mixture.
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Differentiate between homogeneous and heterogeneous mixtures with examples.
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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.
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How are sol, solution and suspension differ from each other ?
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How will you separate a mixture containing kerosene and petrol (difference in their building points is more than 25°C), which are miscible with each other?
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Name the technique to separate
(i) butter from curd (ii) salt from sea water (iii) camphor from salt
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What type of mixtures are separated by the technique of crystallization?
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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) passing of electric current through water and the water breaking down into hydrogen and oxygen
(6) dissolving common salt in water
(7) making a fruit salad with raw fruits
(8) burning of paper and wood
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Try segregating the things around you as pure substances or mixtures.
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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) Find mud particles suspended in water.
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Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
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Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).
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Substance Dissolved
|
Temperature in K
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283
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293
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313
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333
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353
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Potassium nitrate
Sodium chloride
Potassium chloride
Ammonium chloride
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(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K ?
(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 293 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 ?
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Explain the following giving examples.
(a) saturated solution (b) pure substance
(c) colloid (d) suspension
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Classify each of the following as a homogeneous or heterogeneous mixtures.
Soda water, wood, air, soil, vinegar, filtered tea
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How would you confirm that a colourless liquid given to you is pure water?
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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
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Identify the solutions among the following mixtures.
(a) Soil (b) sea water (c) air (d) coal (e) soda water
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Which of the following will show "Tyndall effect"?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution
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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
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Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle
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question_answer22)
Which of the following statements are true for pure substances?
(i) Pure substances contain only one kind of particles.
(ii) Pure substances may be compounds or mixtures.
(iii) Pure substances have the same composition
throughout.
(iv) Pure substances can be exemplified by all elements
other than nickel.
(a) (i) and (ii) (b) (i) and (iii) (c)
(iii) and (iv) (d) (ii) and (iii)
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question_answer23)
Rusting of an article made up of iron is called
(a) corrosion and it is a physical as well as chemical
change
(b) dissolution and it is a physical change
(c) corrosion and it is a chemical change
(d) dissolution and it is a chemical change
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question_answer24)
A mixture of sulphur and carbon disulphide is
(a) heterogeneous and shows Tyndall effect
(b) homogeneous and shows Tyndall effect
(c) heterogeneous and does not show Tyndall effect
(d) homogeneous and does not show Tyndall effect
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question_answer25)
Tincture of iodine has antiseptic properties. This
solution is made by dissolving
(a) iodine in potassium iodide (b)
iodine in vaseline
(c) iodine in water (d)
iodine in alcohol
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question_answer26)
Which of the following are homogeneous in nature?
(i) Ice (ii) Wood (iii)
Soil (iv) Air
(a) (i) and (iii) (b) (ii) and
(iv) (c) (i) and (iv) (d) (iii) and (iv)
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question_answer27)
Which of the following are physical changes?
(i) Melting of iron metal (ii) Rusting of iron (iii)
Bending of an iron rod
(iv) Drawing a wire of iron metal
(a) (i), (ii) and (iii) (b) (i), (ii) and (iv)
(c) (i), (iii) and (iv) (d) (ii), (iii) and (iv)
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question_answer28)
Which of the following are chemical changes?
(i) Decaying of wood (ii) Burning of wood (iii)
Sawing of wood
(iv) Hammering of a nail into a piece of wood
(a) (i) and (ii) (b) (ii) and (iii) (c)
(iii) and (iv) (d) (i) and (iv)
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question_answer29)
Two substances, A and B were made to react to form a third
substance, 
according
to the following reaction 
. Which
of the following statements concerning this reaction are incorrect?
(i) The product shows
the properties of substances A and B.
(ii) The product will always have a fixed composition.
(iii) The product so formed cannot be classified as a
compound.
(iv) The product so formed is an element.
(a) (i), (ii) and (iii) (b) (ii), (iii) and
(iv) (c) (i), (iii) and (iv) (d) (ii), (iii) and (iv)
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question_answer30)
Two chemical species X and Y combine together to form a
product P which contains both X and 
and Y
cannot be broken down into simpler substances by simple chemical reactions.
Which of the following concerning the species X, Y and P are correct?
(i) P is a compound (ii)
X and Y are compounds
(iii) X and Y are elements (iv)
P has a fixed composition
(a) (i), (ii) and (iii) (b) (i), (ii) and
(iv) (c) (ii), (iii) and (iv) (d) (i), (iii) and (iv)
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question_answer31)
Suggest separation technique(s) one would need to employ
to separate the following mixtures.
(a) Mercury and water (b)
Potassium chloride and ammonium chloride
(c) Common salt, water and sand (d)
Kerosene oil, water and salt
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question_answer32)
Which of the tubes in Figure (a) and (b) will be more
effective as a condenser in the distillation apparatus?
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question_answer33)
Salt can be recovered from its solution by evaporation.
Suggest some other technique for the same?
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question_answer34)
The 'sea-water' can be classified as a homogeneous as well
as a heterogeneous mixture. Comment.
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question_answer35)
While diluting a solution of salt in water, a student by mistake
added acetone (boiling point 56°C). What technique can be employed to get back
the acetone? Justify your choice.
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question_answer36)
What would you observe when
(a) a saturated solution of potassium chloride prepared at
60°C is allowed to cool at room temperature?
(b) an aqueous sugar solution is heated to dryness?
(c) a mixture of iron filings and sulphur powder is heated
strongly?
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question_answer37)
Explain why particles of a colloidal solution do not
settle down when left undisturbed, while in the case of a suspension they do?
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question_answer38)
Smoke and fog both are aerosols. In what way are they
different?
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question_answer39)
Classify the following as physical or chemical properties.
(a) The composition of a sample of steel is : 98% iron,
1.5% carbon and 0.5% other elements.
(b) Zinc dissolves in hydrochloric acid with the evolution
of hydrogen gas.
(c) Metallic sodium is soft enough to be cut with a knife.
(d) Most metal oxides form alkalis on interacting with
water.
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question_answer40)
The teacher instructed three students 'A', 'B' and 'C
respectively to prepare a 50% (mass by volume) solution of sodium hydroxide
(NaOH).
'A' dissolved 50g of NaOH in 100 mL of water. 'B'
dissolved 50g of NaOH in 100g of water while 'C dissolved 50g of NaOH in water
to make 100 mL of solution. Which one of them has made the desired solution and
why?
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question_answer41)
Name the process associated with the following
(a) Dry ice is kept at room temperature and at one
atmospheric pressure.
(b) A drop of ink placed on the surface of water contained
in a glass spreads throughout the water.
(c) A potassium permanganate crystal is in a beaker and
water is poured into the beaker with stirring.
(d) A acetone bottle is left open and the bottle becomes
empty.
(e) Milk is churned to separate cream from it.
(f) Settling of sand when a mixture of sand and water is
left undisturbed for some time.
(g) Fine beam of light entering through a small hole in a
dark room.
Illuminates the particles in its paths.
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question_answer42)
You are given two samples of water labelled as 'A' and 'B'.
Sample 'K boils at 100°C and sample 'Q' boils at 102°C.Which sample of water
will not freeze at 0°C? Comment.
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question_answer43)
What are the favourable qualities given to gold when it is
alloyed with copper or silver for the purpose of making ornaments?
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question_answer44)
An element is sonorous and highly ductile. Under which
category would you classify this element? What other characteristics do you
expect the element to possess?
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question_answer45)
Give an example each for the mixture having the following
characteristics.
Suggest a suitable method to separate the components of
these mixtures.
(a) A volatile and a non-volatile component.
(b) Two volatile components with appreciable difference in
boiling points.
(c) Two immiscible liquids.
(d) One of the components changes directly from solid to
gaseous state.
(e) Two or more coloured constituents soluble in some
solvent.
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question_answer46)
Fill in the blanks.
(a) A colloid is a??......... mixture and its components
can be separated by the technique known as?...........
(b) Ice, water and water vapour look different and display
different??......... properties but they are?........... the same.
(c) A mixture of chloroform and water taken in a
separating funnel is mixed and left undisturbed for some time. The upper layer
in the separating funnel will be of.............. and the lower layer will be
that of
(d) A mixture of two or more miscible liquids, for which
the difference in the boiling points is less than 25 K can be separated by the
process called ......... .
(e) When light is passed through water containing a few
drops of milk, it shows a bluish tinge. This is due to the?........... of light
by milk and the phenomenon is called?......... . This indicates that milk is a
......... solution.
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question_answer47)
Sucrose (sugar) crystals obtained from sugarcane and
beetroot are mixed together. Will it be a pure substance or a mixture? Give
reasons for the same.
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question_answer48)
Give some examples of Tyndall effect observed in your
surroundings?
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question_answer49)
Can we separate alcohol dissolved in water by using a
separating funnel?
If yes, then describe the procedure. If not, explain.
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question_answer50)
On heating calcium carbonate gets converted into calcium
oxide and carbon dioxide.
(a) Is this a physical or a chemical change?
(b) Can you prepare one acidic and one basic solution by
using the products formed in the above process? If so, write the chemical
equation involved.
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question_answer51)
Non-metals are usually poor conductors of heat and
electricity. They are non-lustrous, non-sonorous, non-malleable and are
coloured.
(a) Name a lustrous non-metal.
(b) Name a non-metal which exists as a liquid at room
temperature.
(c) The allotropic form of a non-metal is a good conductor
of electricity. Name the allotrope.
(d) Name a non-metal which is known to form the largest
number of compounds.
(e) Name a non-metal other than carbon which shows
allotropy.
(f) Name a non-metal which is required for combustion.
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question_answer52)
Classify the substances given in Figure into elements and
compounds.
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question_answer53)
Which of the following are not compounds?
(a) Chlorine gas (b) Potassium chloride (c)
Iron (d) Iron sulphide
(e) Aluminium (f) Iodine (g)
Carbon (h) Carbon monoxide
(i) Sulphur powder
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question_answer54)
Fractional distillation is suitable for separation of miscible liquids
with a boiling point difference of about 25 K or less. What part of fractional distillation
apparatus makes it efficient and possess an advantage over a simple
distillation process. Explain using a diagram.
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question_answer55)
(a) Under which category of mixtures will you classify
alloys and why?
(b) A solution is always a liquid. Comment.
(c) Can a solution be heterogeneous?
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question_answer56)
Iron filings and sulphur were mixed together and divided
into two parts, 'A' and 'B'. Part 'A' was heated strongly while part 'B' was
not heated.
Dilute hydrochloric acid was added to both the parts and
evolution of gas was seen in both the cases. How will you identify the gases
evolved?
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question_answer57)
A child wanted to separate the mixture of dyes
constituting a sample of ink. He marked a line by the ink on the filter paper
and placed the filter paper in a glass containing water as shown in figure. The
filter paper was removed when the water moved near the top of the filter paper.
(a) What would you expect to see, if the ink contains
three different coloured components?
(b) Name the technique used by the child.
(c) Suggest one more application of this technique.
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question_answer58)
A group of students took an old shoe box and covered it
with a black paper from all sides. They fixed a source of light (a torch) at
one end of the box by making a hole in it and made another hole on the other
side to view the light. They placed a milk sample contained in a beaker/tumbler
in the box as shown in the Figure. They were amazed to see that milk
taken in the tumbler was illuminated. They tried the same
activity by
taking a salt solution but found that light simply passed
through it?
(a) Explain why the milk sample was illuminated? Name the
phenomenon involved.
(b) Same results were not observed with a salt solution.
Explain.
(c) Can you suggest two more solutions which would show
the same effect as shown by the milk solution?
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question_answer59)
Classify each of the following, as a physical or a
chemical change. Give reasons.
(a) Drying of a shirt in the sun.
(b) Rising of hot air over a radiator.
(c) Burning of kerosene in a lantern.
(d) Change in the colour of black tea on adding lemon
juice to it.
(e) Churning of milk cream to get butter.
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question_answer60)
During an experiment the students were asked to prepare a
10% (mass/mass) solution of sugar in water. Ramesh dissolved 10 g of sugar in
100 g of water while Sarika prepared it by dissolving 10 g of sugar in water to
make 100 g of the solution.
(a) Are the two solutions of the same concentration?
(b) Compare the mass % of the two solutions.
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question_answer61)
You are provided with a mixture containing sand, iron
filings, ammonium chloride and sodium chloride. Describe the procedures you would
use to separate these constituents from the mixture?
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question_answer62)
Arun has prepared 0.01% (by mass) solution of sodium
chloride in water.
Which of the following correctly represents the
composition of the solutions?
(a) 1.00 g of NaCl + 100 g of water (b)
0.11 g of NaCl + 100 g of water
(c) 0.01 g of NaCl + 99.99 g of water (d)
0.10 g of NaCl + 99.90 g of water
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question_answer63)
Calculate the mass of sodium sulphate required to prepare its 20% (mass per
cent) solution in 100 g of water?
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