Skip to content
CNMS ICSE - 7 Std
Share
Explore

Answers to textbook exercises

Prepared by: learnloophq@gmail.com

Chapter: 01. Physical Quantities And Measurement

⁠

CONNECT (PAGE 1)

Match the measures of the objects with the most suitable units to measure.
Length of paper: cm
Breadth of suitcase: cm
Weight of milk packet: L (commercially marked by volume)
Length of pen: cm
Weight of oranges: kg
Length of cloth: m
Weight of medicine (tablets): mg
Weight of paper clip: g
⁠

CHECK YOUR PROGRESS (PAGE 6)

Volume of a box of length 5 cm, breadth 3 cm and height 1 cm is
c. 15 cm³
Volume of a cubical box of side 12 cm is
a. 1728 cm³
⁠

REASON CORNER (PAGE 6)

Jasmine used a measuring cylinder to measure the volume of a coin. She recorded her measurement as “about 2 cubic centimetres”. Jasmine’s teacher asked her to make a more accurate estimate. Which of the following is the best way to get a more accurate estimate of the volume of the coin?
c. Measure the total volume of ten similar coins together and divide by 10.
Among the units of volume cm³, m³, litre and millilitre, which is most suitable for measuring the volume of the following?
a. a bathtub: litre
b. a football: cm³
c. a juice bottle: millilitre (or litre)
d. a book: cm³
⁠

REASON CORNER (PAGE 9)

Without using a measuring scale, how will you find out the height of a triangle if you know its area and length of the base?
Height = (2 × Area) / Base (Derived by rearranging the area formula: Area = 1/2 × Base × Height).
What instruments will you use to measure the areas of the following objects?
a. school playground: Measuring tape (to measure length and breadth, then calculate area).
b. your room: Measuring tape.
c. a coin: Vernier calliper (to measure radius, then calculate area) or a graph paper.
d. your notebook: Ruler (to measure length and breadth, then calculate area).
e. your eraser: Ruler or a graph paper.
⁠

MY QUESTION TIME (PAGE 9)

Frame a question on each of the following topics and discuss their answers.
a. Measurement of volume:
Question: Why do we read the lowest level of the meniscus for water but the highest level for mercury when measuring volume in a cylinder?
Answer: Water wets the glass, forming a downward-curving concave meniscus (read at the lowest point). Mercury does not wet the glass, forming an upward-curving convex meniscus (read at the highest point).
b. Measurement of area:
Question: Can we find the exact surface area of an irregular object like a leaf using a graph paper?
Answer: No, we can only obtain an approximate estimation of the surface area by counting the complete and almost complete squares inside the outline.
⁠

SCIENCE TALK (PAGE 13)

How will you measure the density of a liquid other than water? Work in pairs. Discuss and design an activity to do this. Be sure to mention steps to measure the mass and volume of the liquid.
Steps to measure the density of a liquid (e.g., cooking oil):
Measure the mass of the empty measuring cylinder: Place a clean, dry graduated cylinder on a physical balance and record its mass as
⁠
.
Measure the volume of the liquid: Pour a specific volume of the liquid (e.g., 50 mL) into the cylinder and note this volume as
⁠
.
Measure the total mass: Place the cylinder with the liquid back on the balance and record the combined mass as
⁠
.
Calculate the mass of the liquid: Subtract the empty cylinder mass from the total mass:
⁠
.
Calculate the density: Use the formula:
⁠
.
⁠

CHECK YOUR PROGRESS (PAGE 13)

The speed of very slow moving things is usually expressed in
a. cm/s.
Density of air is
b. 1.20 kg/m³
⁠

MY QUESTION TIME (PAGE 14)

Frame a question on each of the following topics and discuss their answers.
a. Measurement of density:
Question: How do chemists use density in practical applications?
Answer: Chemists use density to test the purity of various substances, as pure substances have specific, characteristic densities.
b. Measurement of speed:
Question: If a train travels a distance of 320 km in 4 hours, what is its speed?
Answer: Speed = Distance / Time = 320 km / 4 h = 80 km/h.
⁠

LIFE SKILLS (PAGE 13/14)

A car is travelling at 130 km/h on the Mumbai–Pune highway to reach Pune before 6 p.m. on the same day. It takes 6 h to reach Pune. When do you think the person should start? What is the distance travelled by the car? Make a list of the safety rules that the person needs to follow.
Starting time: The person should start before 12:00 p.m. (noon) to reach before 6 p.m.
Distance travelled: 780 km (Distance = Speed × Time = 130 km/h × 6 h = 780 km).
Safety rules to follow:
Reduce and adjust speed to stay within the legal and safe speed limits of the highway.
Wear seatbelts at all times.
Maintain a safe following distance from other vehicles.
Avoid distractions such as using mobile phones while driving.
Take short breaks to avoid driver fatigue over the 6-hour journey.
⁠

PREPPING FOR PISA (PAGE 14)

What will happen when warm water is added to water at room temperature?
a. Warm water will float as it is less dense than water at room temperature.
There are three beakers A, B and C containing the same amount of water. The temperature of the beakers is 23°C, 41°C and 35°C, respectively. The correct arrangement of the beakers in the descending order of their densities is:
c. A, C, B
⁠

EVACUATION

A. Choose the correct option.

The standard unit of volume in SI system is
c. m³.
How many litres make 1 m³?
c. 1000
If a substance of mass 25 g has a volume of 10 cm³, its density is
a. 2500 kg/m³. (Density = 25 g / 10 cm³ = 2.5 g/cm³ = 2500 kg/m³)
The formula to find the area of a circle with radius r is
a. πr².
Graduated cylinders, graduated beakers, flasks, pipettes and burettes are some of the apparatus used to measure
b. volume.
Equal masses of two substances can have different volumes when they have [HOTS]
d. different densities.

B. Name the following.

the amount of surface covered by an object
Area
the internal volume of a container
Capacity
mass per unit volume of a substance
Density
a metal or glass jar with an overflow outlet
Overflow jar

C. Fill in the blanks.

1 m² is the area of a square with each side of length 1 metre.
1 g/cm³ = 1000 kg/m³.
To measure the volume of an irregular solid which dissolves in water, we use kerosene instead of water.
A piece of stone displaces 25 mL of water. Its volume is 25 cm³.
A measuring container / measuring vessel is used to measure the volume of petrol.

D. Write true (T) or false (F) against the following statements.

Equal volumes of two substances will always have the same mass.
False (F)
1 mL = 100 cm³
False (F)
1 kg of iron contains the same amount of matter as 1 kg of peas.
True (T)
The surface of a liquid poured into a measuring cylinder is always in the form of a convex curve.
False (F)
To measure the density of a substance, its mass and volume should be known.
True (T)

E. Short-answer-type questions.

What do you understand by area? State its SI unit.
Area is the amount of surface covered by an object or a place. Its SI unit is the square metre (m²).
What is volume? Give its SI unit.
Volume is the three-dimensional space occupied by a substance. Its SI unit is the cubic metre (m³).
What are the different units to measure speed? When is each unit used?
The different units to measure speed are:
metre per second (m/s): Used as the standard SI unit of speed.
kilometre per hour (km/h): Used for fast-moving vehicles like cars, trains, and planes.
centimetre per second (cm/s): Used for very slow-moving objects (like snails or glaciers).
What do you mean by meniscus?
Meniscus is the curved boundary surface formed on the top of a liquid when it is poured into a narrow container, such as a measuring cylinder.
Which method is used to measure the volume of irregular solids? What is the principle behind this method?
The method used is the liquid displacement method. The principle is that when an insoluble solid is completely immersed in a liquid, it displaces a volume of the liquid equal to its own volume.
Differentiate between concave meniscus and convex meniscus.
The differences are:
Concave meniscus: Curves downwards. Formed by liquids that wet the sides of the container (e.g., water, kerosene). Reading is taken at the lowest point of the curve.
Convex meniscus: Curves upwards. Formed by liquids that do not wet the container walls (e.g., mercury). Reading is taken at the highest point of the curve.

F. Long-answer-type questions.

Describe an activity to find the area of a rose petal.
Activity to find the area of a rose petal:
Aim: To estimate the surface area of a rose petal using a graph paper.
Materials required: A graph paper (with 1 cm² grids), a rose petal, and a pencil.
Procedure:
Place the rose petal flat on the graph paper and trace its boundary outline with a pencil.
Remove the petal.
Count the number of complete squares enclosed within the outline.
Count the number of squares that are half or more than half complete (almost complete). Ignore any squares that are less than half inside.
Add the number of complete squares and almost complete squares together.
Observation: The total sum represents the approximate surface area in square centimetres (cm²).
How would you measure the volume of an irregular solid which is insoluble in water, using a measuring cylinder?
Steps to measure the volume of an irregular solid:
Procedure:
Fill a graduated cylinder with a suitable amount of water (enough to submerge the solid completely but not overflow).
Note the initial water level reading at the lowest point of the concave meniscus. Let this be
⁠
.
Tie the irregular solid with a piece of fine thread.
Lower the solid gently into the water until it is fully submerged.
Note the new elevated water level reading as
⁠
.
Calculation: The volume of the solid is calculated as:
⁠
. Since
⁠
, the volume difference directly gives the volume of the solid in cubic centimetres.
⁠

Higher Order Thinking Skills (HOTS)

Given below are three boxes containing identical tennis balls. Given that the mass of box A and box B is the same, identify the correct statements regarding their densities.
c. ii and iii (Since Box A and Box B have the same mass and identical outer volume, their overall densities must be equal (ii). Box C is larger and has fewer balls, meaning its density is less than Box A (iii).)
A small stone is immersed in a measuring cylinder and the water level is recorded before and after the stone is immersed. If the mass of the stone is 0.2 kg, then calculate the density of the stone (in g/cm³).
Density = 5 g/cm³ (assuming standard textbook values of water rising from 50 mL to 90 mL):
Mass (
⁠
) =
⁠
⁠
Volume (
⁠
) =
⁠
⁠
⁠
⁠
​(Note: If the water levels on your printed diagram are different, substitute your diagram’s values into:
⁠
)
⁠

Numericals

Find the volume of a stone in cm³, if the water level rises from 18 mL to 29 mL on immersing it in water.
11 cm³ (Volume
⁠
).
The mass of a piece of lead is 232 g and its volume is 20 cm³. Find the density of lead in kgm⁻³.
11600 kgm⁻³ (Density
⁠
).
A substance having a density of 0.8 g/cm³ has a mass of 64 g. What is its volume?
80 cm³ (Volume
⁠
).
The density of zinc is 5.1 g/cm³. Find the mass of the zinc of volume 86 cm³.
438.6 g (Mass
⁠
).
⁠

Integrate • Mathematics

What are the densities of the planets of the solar system? Arrange the values in decreasing order in a bar graph.
Decreasing order of planetary densities (in g/cm³):
Earth: 5.51 g/cm³
Mercury: 5.43 g/cm³
Venus: 5.24 g/cm³
Mars: 3.93 g/cm³
Neptune: 1.64 g/cm³
Jupiter: 1.33 g/cm³
Uranus: 1.27 g/cm³
Saturn: 0.69 g/cm³ ​(To represent this as a bar graph, plot the planets on the horizontal X-axis and their densities from 0 to 6 g/cm³ on the vertical Y-axis, drawing decreasing bars from Earth to Saturn).
Which of these are sold by mass and which are sold by volume? Why?
Classification and reasons:
Gallery
 
Want to print your doc?
This is not the way.
Try clicking the ··· in the right corner or using a keyboard shortcut (
CtrlP
) instead.