Page 2 - Lesson Notes

Solubility:-

Solubility of a substance generally means the ability of the substance to dissolve in
water. Materials can be classified based on their solubility in water. They are of two
groups (considering solid materials)

Soluble in water- Few substances (called solute)are dissolved in water(act as
solvent), they are said to be soluble in water like sugar, common salt.
Insoluble in water- Some materials are not dissolved in water, they are called
insoluble substances. E.g, sand, chalk powder,

For liquids, they are classified into two groups.

Miscible liquids- Liquids which mix together completely, are known as miscible
liquids. As for examples lemon juice, milk, glycerine mix with water.
Immiscible liquids- Liquids which do not mix with one another are called
immiscible liquids. Eg. kerosene oil, cooking oil etc with water.

Like solids and liquid, some gases are also soluble in water. Example- Oxygen, carbon
dioxide etc.

Density and Floatation

Density- Density of a substance is the mass per unit volume.

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The mass of 1 g of water with volume 1cm , has a density of 1g/cm .
A substance which is denser than water sinks into it, whereas a substance which is less
denser than water, floats on it.

That is why a piece of wood, dry leaves float on water and a stone or an iron nail sinks
into water.

Physical State:-

Materials can exsist in three physical states. They are solids, liquids and gases.

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