To observe whether different materials are soluble or insoluble in water 
• Think about the materials like salt, sugar, chalk powder, sand, kerosene oil, vinegar, lime juice and cooking oil.
• Identify whether they are soluble or insoluble in water.
• Record your observations in the table given below. 

Soluble and insoluble materials

S. No.	Materials	Soluble or insoluble
1.	Salt	Soluble
2.	Chalk powder	Insoluble and settles down
3.	Kerosene oil	Insoluble and forms separate layer
4.	Sugar
5.	Sand
6.	Vinegar
7.	Lime juice
8.	Cooking oil

 

(i) The substances which are used in making different objects are called materials.

(ii) Man-made materials are not found in nature but have been made by man on combining two or more natural materials.

(iii) Naturally occurring materials are naturally occurring substances which have been used by man directly for his needs and requirements.

(iv) Placing similar things together is called grouping.

(v) Grouping of different materials on the basis of their size, shape, colour, smell, use, etc., is known as classification of materials.

(vi) Substances which disappear completely upon mixing into water are called water-soluble and those which do not are called water-insoluble. Salt is soluble in water whereas sand is insoluble.

2. Properties of materials :

(i) A material which is difficult to compress or scratch is said to be hard.

(ii) Materials that are shiny, or their freshly cut surfaces are shiny are called lustrous materials and their shine is called lustre.

(iii) Metal is a hard, shiny, solid material which is able to be shaped and can conduct electricity and heat.

(iv) The materials through which things can be seen clearly and light can pass through them are said to be transparent.

(v) The materials through which objects can be seen but not clearly and light can pass partially through them are said to be translucent.

(vi) The materials through which we are not able to see or light cannot pass through them to be opaque.

(vii) An object having an uneven or irregular surface, not smooth or levelled or polished is said to be rough. Ex: Sandpaper.

(viii) Those objects that do not have any bumps or ridges such as silk are smooth.

(ix) Non-metals are commonly soft, broken into pieces on being beaten e.g., carbon, sulphur, oxygen.

(x) A homogeneous mixture of two or more substances such as a mixture of sugar and water is called a solution.