Experiments With Water
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.
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 |
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.
Three States of Water
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.