IS MATTER AROUND US PURE

Calculate the mass of sodium sulphate required to prepare its 20% (mass
percent) solution in 100g of water?

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 + 100g of water
(b) 0.11g of NaCl + 100g of water
(c) 0.0l g of NaCl + 99.99g of water
(d) 0.10 g of NaCl + 99.90g of water

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?

During an experiment the students were asked to prepare a 10% (Mass/Mass)
solution of sugar in water. Ramesh dissolved 10g of sugar in 100g of water
while Sarika prepared it by dissolving 10g of sugar in water to make 100g
of the solution.
(a) Are the two solutions of the same concentration
(b) Compare the mass % of the two solutions.

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.

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?

(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?

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.

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

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.

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.

Can we separate alcohol dissolved in water by using a separating funnel?
If yes, then describe the procedure.
If not, explain.

Give some examples of Tyndall effect observed in your surroundings?

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.

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———.

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.

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?

What are the favourable qualities given to gold when it is alloyed with copper
or silver for the purpose of making ornaments?

You are given two samples of water labelled as ‘A’ and ‘B’. Sample ‘A’ boils
at 100°C and sample ‘B’ boils at 102°C. Which sample of water will not
freeze at 0°C? Comment.

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.

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?

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.

Smoke and fog both are aerosols. In what way are they different?

Explain why particles of a colloidal solution do not settle down when left
undisturbed, while in the case of a suspension they do.

What would you observe when
(a) a saturated solution of potassium chloride prepared at 60°C is allowed
to cool to room temperature.
(b) an aqueous sugar solution is heated to dryness.
(c) a mixture of iron filings and sulphur powder is heated strongly.

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.

The ‘sea-water’ can be classified as a homogeneous
as well as heterogeneous mixture. Comment.

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

Which of the following are chemical changes?

(a) Growth of a plant

(b) Rusting of iron

(c) Mixing of iron fillings and sand

(d) Cooking of food

(e) Digestion of food

(f) Freezing of water

(g) Burning of candle

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

Which of the following will show the "Tyndall effect"?

(a) Salt solution

(b) Milk

(c) Copper sulphate solution

(d) Starch solution

Identify the solutions among the following mixtures:

(a) Soil

(b) Sea water

(c) Air

(d) Coal

(e) Soda water

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

How would you confirm that a colourless liquid given to you is pure water?

Classify each of the following as a homogeneous or heterogeneous mixture.

Soda water, wood, air, soil, vinegar, filtered tea

Explain the following giving examples:

(a) Saturated solution

(b) Pure substance

(c) Colloid

(d) Suspension

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).

Write the steps you would use for making tea. Use the words: solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

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.

What typeof mixtures is separated by the technique of crystallization?

Try segregating the things around you as pure substances or mixtures.

Name the technique to separate

(i) butter from curd

(ii) salt from sea-water

(iii) camphor from salt

Classify the following as chemical or physical changes:

• Cutting of trees

• Melting of butter in a pan

• Rusting of almirah

• Boiling of water to form steam

• Passing of electric current through water, and water breaking down into hydrogen and oxygen gas

• Dissolving common salt in water

• Making a fruit salad with raw fruits

• Burning of paper and wood

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?

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.

How are sol, solution and suspension different from each other?

Differentiate between homogeneous and heterogeneous mixtures with examples.

List the points of differences between homogeneous and heterogeneous mixtures.

What is meant by a pure substance?