Write scientific reasons

A. Graphite is a conductor of electricity.

B. Graphite is not used in ornaments.

C. Limewater turns milky when CO₂ is passed through it.

D. Biogas is an eco-friendly fuel.

A. Graphite is a good conductor of electricity due to the following reasons:

1. In graphite, carbon atoms are arranged in different layers.

2. In each layer, every carbon atom is linked to three neighboring carbon atoms.

3. Thus, the fourth electron of each carbon atom is free to move continuously within the entire layer.

4. Because of the presence of these free electrons in different layers, graphite becomes a god conductor of electricity.

B. Graphite is not used in ornaments due to the following facts:

1. For making ornaments, properties like transparency of substance, reflection of light and hardness should be present.

2. But in graphite, all these properties are absent.

3. It is soft, brittle, black and slippery in nature.

4. Thus, it is not used in making ornaments.

C. When limewater (CaOH)₂ is passed through CO₂, the following reaction takes place:

(CaOH)₂ + CO₂→ CaCO₃ + H₂O

Limewater Calcium

Carbonate

1. In this reaction, when limewater comes in contact with the gas released in the form of an effervescence, it turns milky. This is chemical test for carbon dioxide gas.

2. When limewater turns milky, it is confirmed that the effervescence is of carbon dioxide.

D. Biogas is an ecofriendly fuel:

a. Animal dung, dry leaves, wet garbage get decomposed by anaerobic microbes in a biogas plant.

b. This produces biogas (methane gas).

c. Biogas is a very cheap fuel option which is also used for cooking gas.

d. It is also used for production of an electricity.

e. Biogas contains about 55% to 60% methane and the rest is carbon dioxide.

f. Biogas is a very good manure and is convenient to use.

g. It is a very good manure.