Experiments With Water
Floats or Sinks
Question 1: What will happen when you put a puffed puri in a bowl of water? Would it sink or float?
Answer: It will float
Question 2: What will happen when you put a steel plate on water? Would it sink or float? What would happen to a spoon?
Answer: The steel plate will float on water. The spoon will sink in water.
Question 3: Would the cap of a plastic bottle sink or float on water?
Answer: The cap of plastic bottle will sink in water.
Experiment
Take a big pot filled with water. Take things given in the table. Put each item one-by-one in water. Write your observations.
| Things You Put in Water | Floats |
|---|---|
| Empty bowl | Yes |
| Bowl with 6-7 small pebbles in it | No |
| Iron nail | No |
| Matchstick | Yes |
| Empty plastic bottle with lid closed | Yes |
| Bottle half filled with water | Yes |
| Fully filled bottle | No |
| Aluminium foil open and spread out | Yes |
| Aluminium foil rolled into a ball | No |
| Aluminium foil shaped like a bowl | Yes |
| Soap cake | No |
| Soap cake in soap case | Yes |
| Ice cube | Yes |
Some objects float on water, while some others sink in water. Some objects are lighter than water. Such objects float on water. Some objects are heavier than water. Such objects sink in water.
But a ship is heavier than a nail. Yet the nail sinks in water, while the ship floats on water. Why does this happen?
Whenever an object is immersed in water, the object displaces some water. There are two possibilities.
- If the weight of the displaced water is more than the weight of the object, the object floats on water.
- If the weight of the displaced water is less than the weight of the object, the object sinks in water.
A ship displaces is huge amount of water. The ship is lighter than the water displaced by it. That is why, the ship floats on water.
A needle also displaces water. But nail is heavier than the water displaced by it. That is why, a nail sinks in water.
A steel bowl displaces water. The steel bowl is lighter than water displaced by it. That is why, a steel bowl floats on water.
A steel spoon also displaces water. The spoon is heavier than water displaced by it. That is why, a spoon sinks in water.