Class 9 Science

Mixture

Exemplar Problems

Short Answer Questions

Part 2

Question: 22. What are the favourable qualities given to gold when it is alloyed with copper or silver for the purpose of making ornaments? ed with copper or silver for making of ornaments.

Answer: Since, Gold is a highly malleable metal so it is difficult to make the ornaments with pure gold, thus to make its rigidity desiring gold is alloyed with copper or silver for making of ornaments.

Question: 23. 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?

Answer: Since a metal is sonorous and ductile, thus if an element possesses these qualities this will be kept under the category of metals. The other qualities of metal are good conductor of heat and electricity, lustrous, malleability, etc.

Question: 24. 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.

Answer: The mixture of acetone and water. In this acetone is volatile and water is non-volatile. The mixture of water and acetone can be separated by the process of distillation.

(b) Two volatile components with appreciable difference in boiling points.

Answer: Mixture of acetone and ethanol. The boiling point of acetone is 560C and that of ethyl alcohol is 78.40C.

The mixture of acetone and ethanol can Answer: Mixture of acetone and ethanol. The boiling point of acetone is 560C and that of ethyl alcohol is 78.40C.

The mixture of acetone and ethanol can be separated using fractional distillation. er are two immiscible liquids, thus their mixture can be separated using separating funnel.

(d) One of the components changes directly from solid to gaseous state.

Answer: The mixture of salt and ammonium chloride. In this mixture ammonium chloride changes from solid to gaseous state directly.

The mixture of salt and ammonium chloride can be separated by the process of sublimation.

(e) Two or more coloured constituents soluble in some solvent.

Answer: The ink is the mixture of dyes of many colours. The different dyes of ink can be separated using chromatography.

Question: 25. Fill in the blanks

(a) A colloid is a __________ mixture and its components can be separated by the technique known as _________.

Answer: heterogeneous, centrifugation

(b) Ice, water and water vapour look different and display different _________ properties but they are ___________ the same.

Answer: Physical, chemically

(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 ___________.

Answer: chloroform, water

(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____________.

Answer: Fractional distillation

(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.

Answer: scattering, Tyndall Effect, colloidal

Question: 26. 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.

Answer: Pure substance, since it contains a single component, i.e. sucrose.

Question: 27. Give some examples of Tyndall effect observed in your surroundings?

Answer: Examples of Tyndall Effect:

  • Sunbeam coming from ventilation. The dust particles present in the way of beam looks luminous because of the scattering of light.
  • Milk in a glass appearing faint blue, since milk is a colloid and light passes through it scattered.
  • Sunbeam coming from behind the clouds looks luminous because of the scattering of light.

Question: 28. Can we separate alcohol dissolved in water by using a separating funnel? If yes, then describe the procedure. If not, explain.

Answer: The mixture of alcohol and water cannot be separated using a separating funnel, since these are not immiscible liquids.

The mixture of alcohol and water can be separated by the process of distillation.

Question: 29. On heating calcium carbonate gets converted into calcium oxide and carbon dioxide.

(a) Is this a physical or a chemical change?

Answer: The conversion of calcium carbonate into calcium oxide and carbon dioxide is 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.

Answer: Yes one acidic and one basic solution can be formed by the calcium oxide and carbon dioxide, which are product formed in the above process.

Since metallic oxides are basic and non-metallic oxides are acidic in nature.

Calcium oxide is a metallic oxide. Hence by dissolving it in water a basic solution is formed because of the formation of calcium hydroxide. The reaction involvedCalcium oxide is a metallic oxide. Hence by dissolving it in water a basic solution is formed because of the formation of calcium hydroxide. The reaction involved in this can be written as follows:

CaO + H2O ⇌ Ca(OH)2

Carbon is a non metal hence carbon dioxide is acidic in nature. When it is dissolved in water an acidic solution is formed.

CO2+H2O ⇌ H2CO3

Question: 30. 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.

Answer: Graphite

(b) Name a non-metal which exists as a liquid at room temperature.

Answer: Bromine

(c) The allotropic form of a non-metal is a good conductor of electricity. Name the allotrope.

Answer: Graphite. Graphite is a good conductor of electricity. It is an allotropic form of carbon.

(d) Name a non-metal which is known to form the largest number of compounds.

Answer: Carbon is a non-metal. It is known to form the largest number of compounds.

(e) Name a non-metal other than carbon which shows allotropy.

Answer: Sulphur is a non-metal which shows allotropy. Disulphur and trisulphur are some of the allotropes of sulphur.

(f) Name a non-metal which is required for combustion.

Answer: Oxygen

Question: 31. Classify the substances given in Figure into elements and compounds

Cloud with names of some substances

Answer: Elements: Cu, Zn, O2, F2, Hg, Diamond

Compound: CaCO3, NaCl(aq), H2O,

Question: 32. 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

Answer: Chlorine gas, iron, aluminium, iodine, carbon and sulphur powder are not compounds.


Matter in Our Surroundings

Anything that has both mass and volume is called matter. You can also say that anything which has mass and which occupies space is called matter.

Is Matter Around Us Pure?

Elements and compounds are pure substances. All other substances are mixtures which means they are not pure substances.

Atoms and Molecules

Read about law of conservation of mass, law of constant proportions and Dalton's atomic theory.

Structure of Atoms

Atom is made of three particles; electron, proton and neutron. These particles are called fundamental particles of an atom or sub atomic particles.

Cell: The Fundamental Unit of Life

A cell is capable of independent existence and can carry out all the functions which are necessary for a living being.

Tissue

A groups of cells which is meant for a specific task is called tissue. Tissues are the first step towards division of labour in complex organisms.

Diversity in Living Organisms

Without proper classification, it would be impossible to study millions of organisms which exist on this earth.

Motion

If an object changes its position with respect to a reference point with elapse of time, the object is said to be in motion.

Force & Laws of Motion

Force has numerous effects. Force can set a stationary body in motion. Force can stop a moving body.

Gravitation

Earth attracts everything towards it by an unseen force of attraction. This force of attraction is known as gravitation or gravitation pull.

Work & Energy

When force is exerted on an object and object is displaced, work is said to be done. It means work is the product of force and displacement.

Sound

Sound is a type of energy. Sound travels in the form of wave from one place to another.

Why Do We Fall Ill

Health is a state of physical, mental and social well being. A condition in which the affected person is unable to carry out normal activities is termed as disease.

Natural Resources

Resources which are obtained from nature are called natural resources. Examples: Air, water, soil, wood, etc.

Improvement in Food Production

Food security is said to exist when all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life.