CHEMISTRY [1 Mark Question Answer]

carbon dioxide + water → glucose + oxygen

food + oxygen → carbon dioxide + water vapour + energy

The thin layer of zinc on iron (galvanized iron) does not rust because zinc metal does not corrode on exposure to damp air.

Animals need oxygen for respiration. Oxygen is given out as a by-product during photosynthesis by plants. So animals depend on plants for respiration.

LPG (Liquified Petroleum Gas) is preferred to other fuels as it release more heat energy and less carbon dioxide.
CNG (Compressed natural Gas) is a clean fuel and gives out significantly fewer pollutants.

The chilled water cools the surface of the vessel. As a result, water vapour in the air condenses on the cold surface of the vessel and drops of water are seen.

Electroplating is a method to prevent rusting of iron by coating iron objects by thin layer of tin or chromium metal. Tin and chromium metals are resistant to corrosion.

Galvanization is the process of depositing a thin layer of zinc metal on the surface of iron objects to prevent rusting of iron. Zinc metal does not corrode on exposure to damp air.

Respiration and photosynthesis

When carbon dioxide is passed through lime water, the lime water turns milky.

Air is a mixture (of gases, water vapour, dust particles, etc)

The main components of air are nitrogen (78%) and oxygen (21%). It also contains small amounts of carbon dioxide, water
vapour, inert gases and dust particles.

The blanket of air that envelopes the earth is called atmosphere.