SILICON-10th Science Learning Cards

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CHAPTER-4

SILICON

Learning card-1

1. Write the Atomic Number Atomic mass of silicon.

Silicon Atomic No 14

Atomic mass 28

2. Write the electronic configuration of silicon.

1S2, 2S2, 2P6, 3S2, 3P2

3. Name the two allotropes of silicon.

Amorphous silicon and crystalline silicon

4. Mention any two difference of crystalline and amorphous silicon

Amorphous Silicon

Crystalline Silicon

1. It is a brown powder

1. It is a dark grey, crystalline solid. It roughly resembles the structure of diamond

2. It does not conduct electricity at low temperature.

2. Slightly conducts electricity.

3. It is more reactive than the crystalline variety

3. It is less reactive than the amorphous variety.

4. When heated in the air, it oxidizes at the surface level and it catches fire.

4. It does not burn in the air even when heated.

5. Define exothermic reaction write balanced equation for silicon reacting with steam.

Chemical reactions which liberates heat energy are called exothermic reaction.

Si + 2H2O ---steam--->SiO2 + 2H2

6. Si+C - Sic this reaction is endothermic. Explain.

In this reaction heat is observed or used for chemical reaction so it is an endothermic.

7. How crystalline silicon is obtained from silica?

Crystalline silicon is obtained by reducing silica with coke. When excess of silica is heated with coke in electric furnace in the absence of air crystalline silicon is obtained.

SiO2 + 2e ---heat---> Si + 2C↑

8. Mention any two uses of silicon compounds.

Two uses of silicon compounds:-

a) Zeolite is used in removal of hardness of water.

b) Silicon carbide is used in cutting and grinding tools

9. State the biological significance & hazards of silicon.

Diatoms, radiolarian and siliceous sponges use biogenic silica as structural material to construct skeleton.

Miners and stone breakers, in asbestos factory, glass factory, and cement factory sometimes suffer from a professional hazards called-silicosis.

10. Gel is used in

a) Modern clock b) Chromatography c) Preparation of glass d) Grinding tools

11. The scientist who proved that sand is a compound

a) Robest koch b) Berzelius c) Madame curie d) Faraday

 

CHAPTER-4

SILICON

Learning card-2

1. Name the different ores of Silicon.

Silica or silicates, garnet, zircon, topaz

2. What is the role of Hydrochloric acid & Hydrofluoric acid in extraction of amorphous silicon?

Hydrochloric acid is used to dissolve magnesium oxide, a basic impurity, Hydrofluoric acid is used to remove un reacted silica, by washing.

3. How the crystalline silicon is extracted from silica? What happens if excess silica is not provided in reaction?

Crystalline silicon is obtained by reducing silica with coke. When excess silica is not provided, it will form silicon carbide or carborundum

4. Write any two differences between allotropes of silicon.

Amorphous silicon

Crystalline silicon

1. It is more reactive than the crystalline variety

2. When heated in the air

it oxidizes at the surface

level & it catches fire

1. It is less reactive than amorphous variety

2. It does not burn in the air even when heated

5. Name the compounds of silicon used in the following :

1) Cutting tools,

2) Ornaments

3) Softening of water

4) Manufacture of glass.

1) Silicon Carbide

2) Zircon

3) Zeolite

4) Sand.

6. Define Exothermic and endothermic reactions with one example for each.

Exothermic: Chemical reactions which liberates heat energy are called exothermic reactions.

Si + 2H2O ---steam--> SiO2 + 2H2 ↑

Endothermic: Chemical reaction which absorbs heat are called endothermic reaction

Si + C –--heat--->SiC

7. What are silicones? Mention its uses.

Silicones are polymers of silicon.

Silicones are used in water proofing treatments, moulding compounds, insulating material and other electrical appliances.

8. 1S2, 2S2, 2P6, 3S2, 3P2 is the electronic configurations of an element

a) Sodium b) Potassium c) Carbon d) silicon

9. Granite is polished by

a) Zeolite b) Silicon carbide c) Zircon d) Topaz

CHAPTER-4

SILICON

Learning card-3

1. Name the scientist who proved sand is compound.

Berzelius.

2. Balance the equations given below.-

1) SiO2 + Mg à Si + MgO

2) Si + H2O à SiO2 + H2

1) SiO2 + 2Mg à Si + 2MgO

2) Si + 2H2O à SiO2 + 2H2

3. Name the silicon compounds which used in the is following:

a) Removable of hardness of water b) Construction of house.

c) Manufacture of glass. d) Insulators

a) Zeolite b) Sand c) Sand d) Silicones.

4. What is doping? Why it is carried out?

Trivalent or pentavalent elements is added into pure crystal of silicon or Germanium to produce semiconductor. The process is called doping.

To enrich the conductivity.

5. How the silicon carbide is obtained? Write the chemical equation.

When a mixture of silicon and coke is heated in electric furnace silicon carbide is formed.

Si + C à Sic

6. The acid used to remove unreacted silica in extraction of amorphous silicon.

a) Hydrochloric Acid. b) Hydrofluoric acid c) Nitric Acid d) Sulphuric acid

7. Which silicon compound is used as ornament.

a) Silicons b) Zeolite c) Zircon d) silicon carbide.

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