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.
Dissolves in Water
Experiment
Take 4-5 glasses or bowls, spoons, water and things given in the table. Take some water in each glass. Try to dissolved one thing in one glass. Write your observations.
| Things | Does it dissolve | What happens after keeping for 2 minutes |
|---|---|---|
| Salt | Yes | No change |
| Soil | No | Soil sits on bottom |
| Chalk powder | No | Chalk powder sits on bottom |
| 1 spoon milk | Yes | No change |
| Oil | No | A layer of oil is formed on top |
Soluble Insoluble
Some items dissolve in water, while some items do not dissolve in water. When you mix something in water and the item disappears after sometime, we say that it has dissolved in water. Let us take following examples.
What happens when you put a spoonful of salt or sugar in water and stir the water? Salt or sugar disappears in water. This means that salt or sugar dissolves in water. If an object dissolves in water, we say it is soluble in water. Salt and sugar are soluble in water.
Chalk powder or soil does not dissolve in water. They are insoluble in water. When and object does not dissolve in water, we say it is insoluble in water.
Miscible Immiscible
Some liquids get mixed with water, while some others do not mix with water. For example, milk gets mixed with water. But oil does not mix with water. In this case, we say that milk is miscible in water. Oil is immiscible in water.
Evaporation
Where did the water go?
One day Ayesha's mother put some water to boil on the stove for making tea. She got busy with something and forgot about it. When she remembered and came to check, she found very little water left in the pan.
Think where did the water go?
Answer: The water turned into vapour because of heat.
You have washed your handkerchief and you want to dry it quickly? What all can you do?
Answer: I will put the handkerchief in bright sunlight. If it is the rainy season, then I will put the handkerchief under a fan.
Water is found in three states of matter. The three states of matter are solid, liquid and gas. Water in liquid form is called water. Water in solid form is called ice. Water in gaseous form is called vapour.
When water is heated, some of it changes into vapour. This process is called vapourisation. So, whenever you boil water, some of it turns into vapour.
When water is left in open, some it changes into vapour on normal temperature. This process is called evaporation. Change of water into vapour without boiling is called evaporation. Evaporation happens on all temperatures.
When you keep washed clothes on clothesline, they dry because of evaporation. When a floor is mopped, it becomes dry after some time. This happens because of evaporation. Wind helps in making evaporation faster. That is why, a handkerchief dries faster when it is kept under the fan.
What things do you put in water to make tea? Which of those things dissolves in water?
Answer: I put tea leaves, milk and sugar in water to make tea. Sugar and milk dissolve in water. Tea leaves do not dissolve in water.
You have been given some mishri pieces (lumps of sugar). Suggest some ways to dissolve them quickly.
Answer: I will stir the mixture to dissolve mishri pieces quickly. For making it quicker, I will use warm water.
This shows that things dissolve in warm water quickly than in cold water. This means that a rise in temperature speeds up dissolution.