Lakhmir Singh Manjit Kaur Class 9 Science 2nd Chapter “Is Matter Around Us Pure” Part I solution

Is Matter Around Us Pure (Part I)

Lakhmir Singh and Manjit kaur Class 9 Science Solution – Is Matter Around Us Pure (Part I): Pure Substances and Impure Substances, Elements, Types of Elements, Properties of Metals and Non Metals, Mixtures, Types of Mixtures, Compounds, Differences between Mixtures and Compounds, The case of solutions and Alloys, Solutions, Suspension and Their Properties, Colloids and Their Properties, To Distinguish a Colloid from a solution, The scattering of Light by colloids, Tyndall Effect, Classification of colloids, Concentration of a solution, The case of a liquid solute dissolved in a liquid solvent, Saturated and Unsaturated Solutions, Solubility, Effect of Temperature and and Pressure on Solubility, Separation of Mixtures, Separation of Mixture of Two Solids, Separation of a Mixture of a Solid and a Liquid, Separation by Filtration, Supply of Dinking water in a city, Separation by Centrifugation, Separation of Cream from Milk, Separation by Evaporation, Purification by Crystallation, Separation by Chromatography, To separate the Dyes Present in Black Ink, Separation by Distillation, Separation of Mixture of Tqo Liquids, Separation by Fractional Distillation and Separating Funnel, Separation of Mixtures by Using More than one method.

Very Short Answer Type Questions:

(1) State whether the following statement is true or false:

Milk is a pure substance.

Ans: False.

(2) Name three mixtures found in nature.

Ans. Air

(3) Which of the following is a mixture?

Salt, Air, Water, Alum, Sugar

Ans. Air

(4) Name one metal and one non metal which exist as liquids at room temperature.

Ans. Metal = Mercury; Non Metal = Bromine

(5) Name a metal which is soft and a non metal which is hard.

Ans. Metal: Sodium; Non Metal- Sulphur.

(6) Name a non metal which is good conductor of electricity.

Ans. Graphite.

(7) Name a liquid which can be classified as a pure substance and conducts electricity.

Ans.

(8) Name one solid, one liquid, and one gaseous non metal.

Ans. Carbon (Solid); Bromine (Liquid), Chlorine (Gas).

(9) Name the property:

(a) which allows metals to be hammered into thin sheets.

(b) which enables metals to be drawn into wires.

Ans. (a) Malleability

(b) Ductility

(10) Which type of elements, metals or non metals, show the property of brittleness?

Ans. Oxygen, Water, Hydrogen.

(11) What is meant by saying that metals are malleable and ductile?

Ans. It means that metals can be beaten into thin sheets with a hammer (Without breaking).

(12) What is meant by saying that non-metals are brittle?

Ans. It means that non –metal can not be beaten into thin sheets with a hammer.

(13) What is meant by saying that metals are sonorous?

Ans. This means that metals make a ringing sound when we strike them.

(14) What is meant by saying that metals are lustrous?

Ans. Metals are lustrous or shiny because the shiny surface of metal makes them good reflector of lights.

(15) What is the general name of the materials which contain at least two pure substances and show the properties of their constituents?

Ans. Mixtures.

(16) ‘’The properties of the product are different from those of the constituents’’. State whether this statement best describes an element, a compound or a mixture.

Ans. A compound.

(17) Name one element, one compound and one mixture.

Ans. Element – Sodium

Compound – Soap

Mixture – Soil

(18) What is the major difference between a solution  and ordinary mixture?

(19) What name is given to those elements which are neither good conductors of electricity like copper nor insulators like sulphur?

Ans. Metalloids.

(20) Fill in the following blanks with suitable words:

(a) An element is made up of only one kind of ____

(b) Brine is a _____ whereas alcohol is a ____

(c) Brass is an alloy which is considered a _____

(d) The three important metalloids are _____, ____ and _____

(e) The element which are sonorous are called ______

Ans. (a) atoms (b) Mixture; Compound (c) Mixture (d) Boron; Silicon; Germanium (e) Metals.

Short answer Type Questions Solution:

(21) Classify the following into elements and compounds:

(i) H2O

(ii) He

(iii) Cl2

(iv) CO

(v) Co

Answer: Elements: He, Cl2 and Co

Compounds: H2O and CO

(22) Classify the following as elements or compounds:

Iron, Iron sulphide, Sulphur, Chalk, Washing Soda, Sodium, Carbon, Urea

Answer: Elements – Iron, Sulphur, Chalk, Sodium, Carbon, Urea.

Compounds- Iron sulphide, Washing soda.

(23) What elements do the following compounds contain?      

Sugar, Common salt

Ans. Sugar contains carbon, hydrogen and oxygen.

Common salt contans sodium and chlorine.

(24) What are pure substances? Give two examples of pure substances.

Answer: A pure substance of one which is made up of only one kind of particles.

Two examples of pure substances are:- Hydrogen, Oxygen.

(25) What are the two types of pure substances? Give one example of each type.

Answer: The two types of pure substances are: Elements and Compounds.

Compound: Soap

Elements: Tin

(26) Which of the following are pure substances?

Ice, Milk, Iron, Hydrochloric Acid, Calcium oxide, Mercury, Brick, Wood, Air

Answer: Hydrochloric acid, Calcium oxide, Mercury, Air.

(27) What is the other name of impure substances? Give two example of impure substance.

Answer: The other name of impure substances is Mixtures.

(28) Which of the following substances are elements?

Water, Salt, Mercury, Iron, Marble, Diamond, Wood, Nitrogen, Air Graphite, Hydrogen, Oxygen, Sugar, Chlorine

Answer: Mercury, Iron, Diamond, Nitrogen, Graphite, Hydrogen, Oxygen, Chlorine.

(29) State three reasons why you think air is a mixture and water is compound.

Answer: (i) Air can be separated into its constituents like oxygen, nitrogen, etc, by the physical process of fractional distillation.

(ii) Air shows the properties of all the gases present in it. For example, oxygen supports combustion and air also supports combustion; carbon  dioxide turns lime water milky and air also turns lime water milky, though very, very slowly.

(iii) Heat and light, etc. are neither given out nor absorbed when air is prepared by mixing the required proportions of oxygen, nitrogen, carbon di oxide, argon, water vapour, very slowly.

(30) Name two solid, two liquid, and two gaseous elements at room temperature.

Answer: Two solid: Sodium, Carbon.

Two liquid: Mercury, Bromine

Two gases: Hydrogen and Oxygen.

(31) Explain why, hydrogen and oxygen are considered elements whereas water is not considered an element.

Ans. Hydrogen and Oxygen is considered as element because hydrogen and oxygen can be split up into two or more simpler substances by the usual methods of carrying out chemical reaction by applying heat, light or electricity but water is not considered as element because it can not be split up into two or more substances.

(32) What are three groups into which all the elements can be divided? Name two elements belonging to each group.

Answer:

(33) State two physical properties on the basis of which metals can be distinguished from non metals.

Answer: Metals are malleable and ductile. That is, metals can be hammered into thin sheets and drawn into thin wires. Whereas, Non-metals are brittle. They are neither malleable nor ductile.

Metals are good conductor of heat and electricity whereas, Non metals are bad conductors of heat and electricity  whereas, Non metals are bad conductors of heat and electricity.

(34) Compare the properties of metals and non metals with respect to (i) malleability (ii) ductility and (iii) electrical conductivity.

Ans.

malleability Metals are malleable. Non metals are not malleable.
ductility Metals are ductile Non metals are not ductile
electrical conductivity Metals are good conductor of electricity Non metals are not good conductor of heat of electricity.

(35) State any two properties for believing that aluminum is a metal.

Answer: Aluminum metal is quite malleable and can be converted into thin sheets called aluminium foils.

(36) Give reasons why:

(a) copper metal is used for making electric wires.

(b) graphite is used for making electrode in a dry cell.

Answer: (a) Copper metal is used for making electric wires because it is good conductor of electricity.

(b) This is graphite is used for making electrode in a dry cell.

(37) How would you confirm that a colorless liquid given to you is pure water?

Answer: A very easy solution is to take a sample of colourless liquid and put on stove if it starts boiling exactly at 100 ºC then it is pure water. Any other colourless liquid such as vinegar always have different boiling point. Also observe carefully that after some time whole liquid will convert into vapour without leaving any residue.

(38) Choose the solutions from among the following mixtures:

Soil, Sea water, Air, Coal, Soda water

Answer: Soil, Sea-Water, Air, Soda water.

(39) Is air a mixture or a compound ? Give three reasons for your answer.

Answer: Mixture.

The three reasons are point out below:-

(i) Air can be separated into its constituents like oxygen, nitrogen, etc, by the physical process of fractional distillation.

(ii) Air shows the properties of all the gases present in it. For example, oxygen supports combustion and air also supports combustion; carbon  dioxide turns lime water milky and air also turns lime water milky, though very, very slowly.

(iii) Heat and light, etc. are neither given out nor absorbed when air is prepared by mixing the required proportions of oxygen, nitrogen, carbon di oxide, argon, water vapour, very slowly.

(40) Give two reason for supposing that water is a compound and not a mixture.

Answer: The two reasons are follows:

(i) Water can not be separated into its constituents, hydrogen and oxygen by the physical methods (such as filtration, evaporation, distillation, sublimation, magnet etc.)

(ii) The properties of water are entirely different from those of its constituents, hydrogen and oxygen. For example, water is a liquid whereas hydrogen and oxygen are gases; water does not burn whereas hydrogen burns; water does not support combustion whereas oxygen supports combustion.

(41) Define a compound.  Give two points of evidence to show that sodium chloride is a compound.

Answer: A compound is a substance made up of two or more elements chemically combined in a fixed proportion by mass.

Two points of evidence that sodium chloride is a compound:-

(i) A compound cannot be separated into its constituents by physical processes.

(ii) The properties of a compound are entirely different from those of its constituents.

(42) Define a mixture. Give two points of evidence to show that sugar solution is a mixture.

Answer: A mixture is a substance which consist of two or more elements or compounds not chemically combined together.

Two evidence to show sugar solution is a mixture are follows:-

(i) Energy (in the form of heat, light etc) is usually neither given out nor absorbed in the preparation of a mixture.

(ii) The composition of a mixture is variable, the constituents can be present in any proportion by mass. A mixture does not have a definite formula.

(43) State two reasons for supposing that brass is a mixture and not a compound.

Answer: Brass is considered a mixture because- (i) It shows the properties of its constituents, copper and zinc .

(ii) It has a variable composition.

(44) List five characteristics by which compound can be distinguished from mixtures.

Answer: (i) A mixture can be separated into its constituents by the physical processes.

(ii) A mixture shows the properties of its constituents.

(iii) Energy is usually neither given out nor absorbed in the preparation of a mixture.

(iv) The composition of a mixture is variable, the constituents can be present in any proportion by Mass. A mixture does not have a definite formula.

(v) A mixture does not have a fixed melting point, boiling point, etc.

(45) Explain why, a solution of salt in water is considered a mixture and not a compound.

Answer: A mixture shows the properties of its constituents.

A mixture can be separated into its constituents into its constituents by the physical processes (like filtration, evaporation, sublimation, distillation, solvents, magnet, etc.)

(46) State one property in which a solution of sugar in water resembles a mixture of sugar and sand, and one property in which it differs from it.

Answer:

(47) You are given two liquids, one a solution and other a compound. How will you distinguish the solution from the compound?

Ans. 1 (i) If the substance can be separated into its constituents by physical methods, it is a mixture.

(ii) If the substance cannot be separated into its constituents by physical method, it is a mixture.

  1. (i) If the substance shows the properties of its constituents it is a mixture.

(ii) If the properties of the substance are entirely different from those of its constituents, it is a compound.

  1. (i) If no heat or light etc. is given out or absorbed during the preparation of the substance it is a mixture.

(ii) If heat or light etc, is given our or absorbed during the preparation of the substance, it is a compound.

(48) Name a non metal:

(a) which is lustrous

(b) which is required for combustion

(c) Whose one of the allotropic forms is a good conductor of electricity. Name the allotrope.

(d) other than carbon which shows allotropy.

(e) which is known to form the largest number of compounds.

Answer: (a) Iodine

(b) Oxygen

(c) Carbon / Graphite

(d) Sulphur

(e) Carbon.

(49) Name a metal:

(a) Which can be easily cut with a knife

(b) which forms amalgams.

(c) which has no fixed shape.

(d) which has a low melting point.

(e) which is yellow in color.

Answer: (a) Sodium

(b) Mercury

(c) Mercury

(d) Sodium

(e) Gold

(50) Which of the following are not compounds?

Chlorine gas, Potassium Chloride, Iron powder, Iron sulphide, Aluminium foil, Iodine vapour, Graphite, Carbon monoxide, Sulphur powder, Diamond.

Answer: Chlorine gas, Iron Powder, Aluminium foil, Iodine vapour, graphite and diamond are not compounds. These are different states of an element.
ie., Cl₂, Fe, Al, I₂ and C atoms’ allotropes.

Long Answer Type Questions:

(51) (a) State the main points of difference between homogeneous and heterogeneous mixtures.

(b) Classify the following materials as homogeneous mixtures and heterogeneous mixtures:

Soda-water, Wood, Air, Soil, Vinegar, Alcohol and water mixture, Petrol and Water mixture, Chalk and water mixture, Sugar and water mixture, Copper sulphate solution.

Ans. (a) The main points of difference between homogeneous and heterogeneous mixtures are point out in a tabular form below:-

Homogeneous

Heterogeneous

(i) Those mixtures in which the substances are completely mixed together and are indistinguishable from one another, are called homogeneous mixtures. (i) Those mixtures in which the substances remain separate and one substance is spread throughout the other substance as small particles, droplets or bubbles are called heterogeneous mixtures.
(ii) Some of the examples of homogenous mixture are Sugar solution, Salt solution, Copper sulphate solution, Sea-water Alcohol, Petrol etc. (ii) Some of the examples of Heterogeneous mixtures are: Sugar and sand mixture, Salty and sand mixture, Polluted air, Gunpowder, Milk, Ink, Petroleum, Paint etc.

 

(b) Homogenous Mixtures:- Soda water, Vinegar, Sugar and water mixture, Copper sulphate solution.

Heterogeneous Mixtures:- Wood, Air, Soil, Alcohol and Water mixture, Petrol and water mixture.

(52) (a) What is meant by (i) elements (ii) compounds, and (iii) mixtures? Write down the names of two elements, two compounds and two mixtures.

(b) Classify the following into elements, compounds and mixtures: Marble, Air, Gold, Brass, Sand, Diamond, Graphite, Petroleum, Common salt, Sea-water, Chalk

Answer: (a) (i) Element: An element is a substance which cannot be split up into two or more simpler substances by the usual chemical methods of applying heat, light or electric energy.

(ii) Compounds: A compound is a substance made up of two or more elements chemically combined in a fixed proportion by mass..

(iii) Mixture: A mixture is a substance which consist of two or more elements or compounds not chemically combined together.

Example of Elements: Hydrogen, Oxygen,

Example of compounds: Water, Common Salt.

Example of Mixture: Air, Gunpowder.

(b) Elements: Gold, Diamond, Graphite.

Compounds: Marble, Common salt, Chalk

Mixture: Air, Brass, sand, Petroleum.

(53) (a) What are (i) metals (ii) non-metals (iii) metalloids? Give two examples of metals, non metals and metalloids.

(b) Classify the following into metals, non metals and metalloids.

Silicon, Mercury, Diamond, Sulphur, Iodine, Germanium,  Sodium, Carbon, Magnesium, Copper, Boron, Helium.

Answer: (a) (i) Metal: A metal is an element that is malleable and ductile, and conducts electricity.

(ii) Non metals: A non metal is an element that is neither malleable nor ductile and does not conduct electricity.

(iii) Metalloids: The elements which show some properties of metals and some other properties of non metals are called metalloids.

Examples of Metals: Iron, Copper.

Examples of Non metals: Carbon, Sulphur.

Examples of Metalloids: Boron, Silicon.

(b) Metals: Mercury, Sodium, Magnesium, Copper.

Non Metal: Diamond, Sulphur, Iodine, Carbon, Helium.

Metalloid: Silicon, Germanium, Boron.

(54) (a) What is a mixture? Give two examples of mixtures.

(b) What is meant by (i) Homogeneous mixtures, and (ii) Heterogeneous mixtures? Give two examples of homogeneous mixtures and two of heterogeneous mixtures.

(c) What is the other name of homogenous mixtures?

Answer: (a) A mixture is a substance which consist of two or more elements or compounds not chemically combined together.

Example: Air, Argon.

(b) Homogeneous mixtures: Those mixtures in which the substances are completely mixed together and are indistinguishable from one another are called Homogeneous mixtures.

Heterogeneous mixtures: Those mixtures in which the substances remain separate and one substance is spread throughout the other substance as small particles, droplets or bubbles are called heterogeneous mixtures.

Example of Homogeneous Mixture: Sugar solution, Salt solution.

Example of Heterogeneous Mixture: Sugar and sand mixture, Salt and sand mixture.

(c) The other name of homogeneous mixture are called solution.

(55) (a) What are the three general classes of matter? Give one example of each type.

Answer: (a) The three general classes of matter are Solid, Liquid and Gas.

Solid – Wood.

Liquid – Water.

Gas – Air.


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