__EXCERISE__

__Short-Answer Questions__

**1. Define volume. Write its SI unit.**

**Volume of an object is the space occupied by it. It's S.I unit is m³.**

__Answer__-

**2. What is meant by the density of a body? Write the SI unit of density.**

**The density of a material is defined as its mass per unit volume. The S.I unit of Density is kg/ m³.**

__Answer__-

**3. What is the relative density of a substance? What is its SI unit?**

**The relative density of a substance is defined as the ratio of the density of a substance to that of water. It's has no unit.**

__Answer__-

**4. What is the weight of a body? What is the SI unit of weight?**

**The weight of a body is the force with which it is attracted by gravity. S.I unit of Weight is newton (N).**

__Answer__-

**5. What is the relation between mass and weight?**

**Weight = constant x mass**

__Answer__-

**6. What is the relative density of water?**

**Relative density of water is 1.**

__Answer__-__Long-Answer Questions__:

**1. Draw an irregular shape on a graph paper and explain how you would calculate its area.**

**Irregular shape is placed on the graph paper and outline is drawn.**

__Answer__-

__Calculate__-The number of complete squares within the outline = 17

The number of squares with half or more within the outline = 14

The total number of squares = 31

The area of each square = 1 cm³

The area of the irregular shape = 31 cm³

**2. How would you measure the volume of an irregular solid?**

**We need a measuring cylinder, a small stone which can move easily inside the cylinder, some string and water. Take some water in the cylinder, as in Figure . Read the level of water on the scale marked on the wall of the cylinder. Then tie the string around the stone, and lower it gently into the water till it is completely submerged, as in Figure . Read the level of water again. The difference between the two readings gives the volume of the stone. For the Case shown in Figure**

__Answer__-The initial reading = 20 ml

The final reading = 24 ml

The volumeof the stone= 24 ml- 20 ml

= 4 ml = 4 cm³

**3. How would you determine the density of a cube?**

**To determine the density of a cube , we need to find out mass of the cube using physical balance and volume by using formula.**

__Answer__-Density of a cubex= Mass of a cube ÷ Volume of a cube.

**4. Distinguish between the density and relative density of a substance.**

**The density of a material is defined as its mass per unit volume. The S.I unit of Density is kg/ m³**

__Answer__-

**Objective Questions**

__Choose the correct option__.

**1. Which of the following is not a unit of volume?**

(a) cc

(b) mL

**(c) m² **

(d) L

**2. A density of 1 g/cc can be expressed as**

**(b) 1000 kg/m³**

**3. The weight of an object of mass 1 kg is**

**(a) 9.8 N.**

(b) 1 N

(c) 98 N

(d) 0.98 N

**4. Which of the following would sink in water**?

(a) Kerosene (800 kg/m³)

(b) Ice (916 kg/m³)

(c) Cork (200 kg/m³)

**(d) Mercury (13600 kg/m³)**

**5. Which of the following changes with the place where it is measured?**

(a) Mass

**(b) Weight**

(c) Volume

(d) Area

__Fill in the blanks__.

1. The capacity of a container is the

__of the liquid it can hold.__

**volume**2. The unit of capacity is the same as

**volume**3. A substance of relative density greater than 1 is

__than water.__

**heavier**4. The mass of a body is the amount of

__in the body.__

**matter**5. The greater the mass of a body, the

__is its weight.__

**more**

__Write True or False__.

1. The area of a piece of cardboard of irregular shape can be found by using a string and a scale.

**False**

2. The relative density of a substance has the same numerical value as its density in SI units.

**False**

3. A substance with a relative density of less than 1 is lighter than water.

**True**

4. The greater the mass of a body, the greater is its volume.

**False**

5. The density of water is 1000 kg/m³.

**True**

6. Ice is lighter than water.

**True**

7. Weight is a force.

**True**

__Numericals__:

**1. Find the mass of an ice cube of edge 2 cm. The density of ice is 9000 kg/m³.**

__Answer__-

Density = 9000 kg/ m³ = 9 g/ cm³

Volume = 2x2x2 = 8 cm³

Density = Mass ÷ Volume

Mass = Density x Volume

= 9 g/ cm³ x 8 cm³ = 72 g

**2. A beaker weighs 120 g when empty and 200 g when filled with kerosene. Find the volume of the beaker. The density of kerosene is 800 kg/m³.**

__Answer__-

Density = 800 kg / m³ = 0.8 g/ cm³

Mass of kerosene = 200 g - 120 g = 80 g

Volume = Mass ÷ Density

= 80 g ÷ 0.8 g/ cm³ = 100 cm³

**3. A metal ball weighs 1.8 kg. The volume of the ball is 250 cc. Find the density of the metal**.

__Answer__-

Given Mass = 1.8 kg = 1800 g

Volume = 250 cm³

Density = Mass ÷ Volume

= 1800 g ÷ 250 cm³

. = 7. 2 g / cm³ = 7200 kg / m³

**4. A metallic object of irregular shape displaces 21 mL of water when it is immersed in a measuring cylinder containing water. If its mass is 56.7 g, what is the density of the metal?**

__Answers__:

Volume of metal = 21 ml = 21 cm³

Mass = 56.7 g

Density = Mass ÷ Volume

. = 56.7 g ÷ 21 cm³

= 2.7 g/ cm³