AIM : To prove that some solids are soluble in water.
Material required : (i) A rack of test tubes (ii)water (iii)common salt (iv)sugar (v)washing soda (vi)chalk powder and sand.

Method :  Add a pinch of chalk powder in the first test tube, a pinch of sugar in second test tube, a pinch of common salt in the third test tube, a pinch of sand in the fourth test tube and a pinch of washing soda in the fifth test tube. Pour water into each test tube such that half of each test tube is filled with water. Shake each test tube vigorously and replace in the rack. You will notice that sugar, common salt and washing soda disappear in water, and hence are soluble substances. Sand and chalk powder do not dissolve in water, and hence are insoluble substances. 

Some liquids like vinegar, lemon juice etc. completely mix with water. These liquids are said to be miscible in water. Some others like oil do not mix with water and form a separate layer when kept aside for some time. These liquid are immiscible in water. Some gases are soluble in water whereas others are not. Water, usually, has small quantities of some gases dissolved in it. For example, oxygen gas dissolved in water is very important for the survival of animals and plants that live in water. 

(iv)    Objects may float or sink in water :
Insoluble solids separate out from water. Some of these materials that do not mix with water, float to the surface of water. Others may sink to the bottom of the tumbler.

Some substances like oil, wood etc. float on water while substances like stone, metal piece etc sink in it.

Some objects float in water while others sink in it

AIM : To find out substance which sink/float in water.
Material required : (i) a small stone (ii) a small piece of wood (iii)a coin (iv)a leaf (v)a brass screw 
(vi) a small piece of ice (vii)a glass bowl filled with water. 
Method : Take a glass bowl filled with water. In the water, drop the above mentioned substances one by one and observe what happens. We will notice that the stone, the key, the coin and the brass screw sink in water. Thus, they can be grouped as substances heavier than water.

Fig. Material which sink or float in water

We will notice that the wax, the plastic ball, the wood, the leaf and ice float on the surface of water. Thus, they can be grouped as substances lighter than water. We can repeat the activity by dropping the above substances in kerosene oil or any other liquid and find out which float or sink in it.

(v)    Transparency : 
Those substances or materials, through which things can be seen, are called transparent. Light passes completely through these materials. Glass, water, air and some plastics are examples of transparent materials.
On the other hand, there are some materials through which we are not able to see i.e. light does not pass  through them. These materials are called opaque. Wood, cardboard and metals, are example of opaque materials. 

The materials through which light passes partially and objects can be seen but not clearly, are known as translucent. We can therefore group materials as opaque, transparent and translucent.

Looking through opaque, transparent or translucent material

Our palm is also translucent. When we put palm on torch then partially  light passes through the hand. It prooves that our palm is also translucent.

Does torch light pass through your palm?


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