Measurement of Volume and Density
• The space occupied by an object is called its volume.
• The S.I unit of volume is cubic metre and is denoted by symbol m3.
• Other units of volume are cm3 and mm3, where 1 cm3 = 106 m3 and 1 mm3 = 109 m3.
• The volume of liquids is expressed in litre which is denoted by symbol (l) and milli litre (ml).
• 1 l = 103 m3 = 1000cm3 and 1ml = 1 cm3.
• The volume of an irregular solid is found by the method of displacement of a liquid using a measuring cylinder.
• The density of a substance is defined as mass per unit volume of that substance. For a body of mass M and volume V, its density d is given by .
• The S.I unit of density is kg m3 and its other unit is g cm3.
• 1 g cm3 = 1000 kg m3.
• The density of a substance does not change with size or shape.
• The density of most substance decreases with increase in temperature because the substances expand on heating. However, the density of water decreases when heated from 0oC to 4oC and then increases on heating above 4oC.
• The density of water is maximum at 4oC equal to 1 g cm3 or 1000 kg m3.
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Q1
Find volume of a book of length 30 cm, breadth 22 cm and height 3 cm.
Marks:1Answer:

Q2
How we can measure the density of irregular objects?
Marks:5Answer:
To calculate the density for irregular objects, volume is measured with the help of the following activity:
 Pour the water in the measuring cylinder to a certain level.
 Note the initial level of the water.
 Tie the irregular body such as stone into the water so that it is completely immersed without touching the sides.
 Note the final water level
 The difference between the final and initial levels gives the volume of the stone.
and mass is measured by the physical balance.
Density can then directly be calculated putting the value of mass and volume in the formula of density.

Q3
The level of water in a measuring cylinder is 15.5 ml. When a stone is lowered in it, the level of water becomes 25.8 ml. Find the volume of the stone.
Marks:2Answer:
The level of water in a measuring cylinder is 15.5 ml.
The level of water, when a stone is lowered in it is 25.8 ml.
Now, volume of stone is the difference between the two readings.
In our case, volume of stone = (25.815.5) ml
= 10.3 ml

Q4
What do you understand by the volume of an object? Give the S.I. unit of volume?
Marks:1Answer:
The amount of space occupied by a threedimensional object or a substance is called volume. The S.I unit of measuring volume is cubic metre (m^{3}).

Q5
Define and state the expression for the density of an object.
Marks:1Answer:
The density of a substance defines the amount of mass it contains in each unit of its volume.
The expression for density is given by: