Lakhmir Singh Physics IS MATTER AROUND US PURE Solutions

Chapter 2 - Is Matter Around Us Pure ? Exercise 57

Question 1 State whether the following statement is true or false:

Milk is a pure substance.

Solution 1 False

Question 2 Name three mixtures found in nature.

Solution 2 Milk, Paint, Glass

Question 3 Which of the following is a mixture?

Salt, Air, Water, Alum, Sugar

Solution 3 Air is a mixture.

Question 4 Name one metal and one non-metal which exist as liquids at room temperature.

Solution 4 Mercury is a liquid metal and bromine is a liquid non-metal

Question 5 Name a metal which is soft and a non- metal which is hard.

Solution 5 Sodium metal is soft and diamond is an extremely hard non-metal.

Question 6 Name a non-metal which is a good conductor of electricity.

Solution 6 Diamond is a non-metal which is good conductor of electricity.

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

Solution 7 Mercury

Question 8 Name one solid, one liquid and gaseous non - metal.

Solution 8 Carbon is a solid non-metal, bromine is a liquid non-metal and chlorine is a gaseous non-metal.

Question 9 Name the property:

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

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

Solution 9

(a). Malleability

(b). Ductility

Question 10 Which type of elements, metal or non- metals, show the property of brittleness ?

Solution 10

Non-metals show brittleness.

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

Solution 11 This means that metals can be drawn into thin sheets and can also be drawn into wires.

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

Solution 12 This means that non-metals break into pieces when they are hammered.

Question 13 What is meant by saying that metals are sonorous ?

Solution 13 This means that metals make a ringing sound when we strike them.

Question 14 What is meant by saying that metals are lustrous ?

Solution 14 This means that metals are shiny in nature.

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

Solution 15 Mixtures.

Chapter 2 - Is Matter Around Us Pure ? Exercise 57

Question 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.

Solution 16 The given statement best describes a compound.

Question 17 Name one element, one compound and one mixture.

Solution 17 Copper is an element, water is a compound and air is a mixture.

Question 18 What is the major difference between a solution and an ordinary mixture?

Solution 18 Mixtures are generally heterogeneous in which there is a boundary separation between different substituents.

Solutions are homogeneous mixtures in which no separation is visible between different materials.

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

Solution 19 Metalloids

Question 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 elements which are sonorous are called ________ .

Solution 20

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

(b).Brine is a mixture whereas alcohol is a compound.

(c).Brass is an alloy which is considered a mixture.

(d).The three important metalloids are boron ,silicon and germanium.

(e).The elements which are sonorous are called metals.

Question 21 Classify the following into elements and compounds:

(i) H2O (ii) He (iii) Cl2 (iv) CO (v) Co

Solution 21 (i). H2O - Compound

(ii). He - Element

(iii). Cl2 - Element

(iv). CO - Compound

(v). Co - Element

Question 22 Classify the following as elements or compound:

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

Solution 22 Elements - Iron, Sulphur, Sodium and Carbon

Compounds - Iron sulphide, Chalk, Washing Soda and Urea

Question 23 What elements do the following compounds contain ?

Sugar, Common salt

Solution 23 Sugar contains carbon, hydrogen and oxygen.

Common salt contains sodium and chlorine.

Question 24 What are pure substances ? Give two examples of pure substances.

Solution 24 A pure substance is one which is made up of only one kind of atoms or molecules. Examples - Oxygen and sugar.

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

Solution 25 Two types of pure substances -

(i). Pure substance made up of same kind of atoms.

Example - Sulphur

(ii). Pure substance made up of same kind of molecules.

Example - Water

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