NCERT Solutions for Class 4th The World Around Us Chapter 7 Which things float and which sink? — Activity 3
Book page 110–111 Updated on2026-09-19
Q1.
Collect objects, such as a leaf, an iron nail, an empty bowl (katori), a plastic bottle with a lid, pieces of stone, aluminium foil and other things of your choice. Fill a bucket with water. Before dropping the things listed in the table, guess whether things will float or sink. You may try other things too. Then, observe what happens when it is actually dropped in water. You can write ‘F’ for objects that float and ‘S’ for objects that sink.
Items
Before dropping
After dropping
What is your guess?
Why do you think so?
What is your observation?
What could be the reason?
Leaf
F
It is light
F
It is light
Iron nail or pin
Empty steel bowl
A piece of stone
Empty bottle with a closed lid
Bottle full of water with a closed lid
The table as it is printed in the book, with the leaf row already filled in as an example.
Answer
What to do
Fill a bucket with water and keep all the things ready beside it.
First guess for each thing — will it float (F) or sink (S)? Write the guess and the reason.
Now put the things in the water one by one, gently.
Write down what really happened and what you think the reason is.
Set-up: fill a bucket with water and keep these things beside it, one at a time.
The completed table
Items
Before dropping — What is your guess?
Before dropping — Why do you think so?
After dropping — What is your observation?
After dropping — What could be the reason?
Leaf
F
It is light
F
It is light
Iron nail or pin
S
It is made of iron and feels heavy
S
Iron is heavy for its small size, so it goes down
Empty steel bowl
S
Steel is heavy
F
It is empty, and its cup shape holds air inside
A piece of stone
S
It is hard and heavy
S
It is heavy for its small size
Empty bottle with a closed lid
F
It is light and full of air
F
The closed bottle is full of air, so it stays on top
Bottle full of water with a closed lid
S
It is full of water and feels heavy
S
There is no air inside it now, so it goes down
Why it happens: The book says it after the activity — some heavy objects like iron nails sink, while lighter ones like leaves float. But the empty steel bowl is heavy and still floats, so weight alone does not decide it.
Tip: Lower the steel bowl into the water slowly and keep it straight. If it tilts, water goes in and then it sinks.