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1. Driving of a a vehicle on a surface

2. Applying brakes to stop a moving vehicle

3. Skating

4. Walking on the road

5. Writing on notebook/ blackboard

6. Flying of aeroplanes

7. Drilling a nail into wall

8. Sliding on a garden slide

9. Lighting a matchstick

10. Dusting a foot mat/ carpet by beating it with a stick 

When we measure speed of light in two different media, relative refractive index of medium 2 with respect to medium 1 is defined as the ratio of speed of light in medium 1 to speed of light in medium 2.

n₂₁= speed of light in 1st medium / speed of light in second medium

Calcium sulphate with half a molecule of water per molecule of the salt (hemi-hydrate) is called plaster of paris (plaster of paris).

It is prepared by heating gypsum (CaSO₄.2H₂O) at 120°C in rotary kilns, where it gets partially dehydrated.

Plaster of paris is a white powder, which when mixed with water sets into a hard mass as crystals of gypsum are produced with evolution of heat. Hence it is used in setting of plaster for fixing broken bones. It is also used in making several decorative items, toys and chemical plugging 

Settling down of heavier insoluble particles/ solids from a mixture is called sedimentation. Like mud settles from muddy water.

Decantation is pouring out of upper clear layer of liquid into another container to separate two immiscible liquids. Like draining oil from a mixture of oil and water after allowing the two to separate and form distinct layers

Filtration is the process of separating insoluble impurities from a solution. When a solution is passed through a filter, particles with pore size bigger than that of the filter are retained while others pass through. Like filtering mud from muddy water

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● Chlorine is used in bleaching powder and liquid bleach, which are used for cleaning purposes.

● Chlorine is also very efficient disinfectant, hence added in public water to kill disease causing pathogens.

● Noble gases such as neon, argon, krypton are used in different types of lights.

● Diamond is used in industries for cutting of glass, etc.

● Coal , another form of carbon, is used as a fuel.

● Nitrogen is used in manufacturing of ammonia.

● Oxygen cylinders are used for breathing in emergency cases.

● iodine is used as tincture iodine