Explore topic-wise InterviewSolutions in .

Objects around us are made of a large variety of materials.

Some materials change their state from solid to liquid, liquid to gas on being heated, and from gas to liquid, liquid to solid on being cool.

Some materials sink in water and some materials can float on water.

Some materials in one shape will sink in water but float on water when they are in another shape.

The materials that can dissolve are said to be insoluble.

The materials that do not dissolve are said to be insoluble.

Some materials change their state from solid to liquid, liquid to gas on being heated, and from gas to liquid, liquid to solid on being cool.

Based on their properties, we use different materials for different purposes. Materials can exist in three important states; solids, liquids, and gases.

The wooden nail will sink to the bottom.

Substances which dissolve in water are said to be soluble substances.

Material: The substance used to make things is called material Ex: Wood, Metal, rock, cotton, etc.

1. Why is the ship not sinking in water though it is made up of iron? 

2. Does iron float in salty water? 

3. Why did such a huge body like ship not sink in sea? 

4. What is the secret of ships floating in the sea?

5. What is the science behind this floating?

The process of separating colours from a mixture of colours is called chromatography.

1. During winnowing, only husk and light particles can be separated from grains. 

2. But small stones and clay pieces will remain in the grains heap as they are heavy. 

3. To remove these stones and other particles, we have to pick them by hand and separate them. 

4. Hence handpicking is necessary after winnowing.

Distillation is used to remove impurities from water.

We use chromatography to separate colours or pigments from their mixtures. 

Ex: 1. 

To separate colours from ink. 

2. To separate colouring pigments from the leaf extract, etc.

Soluble: That can be dissolved in water or any other liquid.

a) Winnowing 

b) Sieving 

c) Handpicking 

d) Filteration 

e) Decantation

Separation: Divide into parts or groups.

Chromatography: A process of separating the component of the mixture by selective absorption of various compounds as identIfiable bands.

1. Tea leaves are separated from tea using a strainer. 

2. The size of the tea leaves is more when compared to the size of the holes in the Strainer. This property helped in the separation of tea leaves from the tea.

Distillation: The process used to remove impurities from liquids by boiling

A solvent Is a liquid that dissolves other substances in it. Water can dissolve more substances than any other solvents. So it is called Universal Solvent.

Crystallization: The process used to separate dissolved solid substances from a liquid by transforming them into crystals.

a) 

1) No. Filteration is used to remove the insoluble substances only. But salt is soluble in water. 

2) So, filtration is not used to obtain pure water from seawater. 

b) 

1) Yes. The decantation method is used to . separate an insoluble substance (cheese) in liquid (milk). 

2) So, it can be removed from curdled milk. 

c) 

1) No. Filtration is used to remove the insoluble substances only. But sugar is soluble in tea it cannot be removed by filtration.

Farmers separate grains which are bigger in size from the smaller ones by sieving. The bigger grains are then used as seeds or sold at a higher price.

Filtration: The process used to separate solids from liquids or gases using a filter medium (Filter paper, Cloth, etc. witch has minute pores) that allows the fluid to pass through but not the solid.

1. We cannot make a cricket baH with mud or glass. 

2. If that ball is struck with the bat it breaks into pieces. 

3. This ball cannot withstand hard strokes.

Sieving: The method used to separate fine particles from large particles in a mixture by using a sieve.

1. No. We cannot make a chair with glass or mud. 

2. Both are brittle materials and can be broken easily.

1. Yes. We can separate mud from muddy water using a sieve. 

2. Mud water can be filtered with filter paper. The pores of the sieve (filter paper) are very small.

Decantation: The separation of the clear upper liquid from the sediment (the separation of mixtures of immiscible liquids or of a liquid and a solid mixture)

The Correct answer is B) Colours.

Correct option is: Cotton

Statements (b), (d) and (e) are not correct. 

(b) Metals are good conductor of electricity and also good conductor of heat. 

(d) Oxides of non-metals are acidic in nature and oxides of metals are basic in nature. 

(e) A more reactive metal replaces a less reactive metal from its salt solution in water.

The tablet is not made of iron metal, instead it contains a salt of iron.

The bulb will not glow as wood is not a good conductor of electricity.

(a) iron 

(b) conductor

Hint: Write the activity based on the fact that when an iron nail is put in a beaker containing copper sulphate solution, iron replaces copper from the solution, since it is more reactive. Copper metal and iron sulphate are the products which are obtained as a result of the chemical reaction.

Correct option is: Water

The green material is a mixture of copper hydroxide and copper carbonate formed due to reaction of copper with moist air (water, oxygen and carbon dioxide).

Correct option is: Natural

Correct option is: Man-made

Correct option is: Plastic bags

1. In the hard water of a well or a tube well, soap does not give lather but forms a scum.

2. As a result soap loses its cleansing property. So soap cannot be used in hard water.

1. The important ingredients of a toothpaste are calcium carbonate and calcium hydrogen phosphate. 

2. They remove the dirt on teeth. These ingredients also polish the teeth. 

3. A certain proportion of fluoride in the tooth paste helps prevent tooth decay. 

4. It is essential for the enamel covering of teeth.

Aluminium is used to make thin foils for packaging medicines, chocolates and food items. This is because it provides a complete barrier to light, oxygen, moisture and bacteria.

1. In the hard water, (of a well or a tube-well), soap does not give lather but forms a scum. 

2. As a result, soap loses its cleansing property. So with help of soap we will come to know that it is a hard water.