General Science Previous Year Questions (PYQ) with Answers – Page 49

Air is optically rarer than water, so light speeds up, not slows down, when it passes from water into air.

In a dicot leaf most stomata are on the lower surface, so coating that surface blocks most of the water loss and the leaf stays fresh the longest.

Photosynthesis gives off oxygen, and oxygen is what aerobic respiration needs to release energy from food. In photosynthesis, green plants use sunlight, carbon dioxide and water to make glucose, and release oxygen, which comes from the splitting of water.

Intercalary meristem lies between mature tissues, at the base of leaves and of internodes. Meristems are tissues whose cells keep dividing.

Cells made by the meristem lose the ability to divide and take on a fixed shape, size and job, and this change is called differentiation.

The oesophagus, like the mouth, is lined by flat squamous epithelium that protects it from wear as food passes. Epithelial tissue covers body surfaces and lines organs, and its cells are named by shape.

Protochordates are marine chordates that have a notochord at some stage but never develop a backbone. The phylum Chordata is split into protochordates and vertebrates.

Jointed legs are the mark of the phylum Arthropoda, to which insects belong; an earthworm has no legs at all.

The enzyme that makes most of the cell's ATP, ATP synthase, sits in the inner mitochondrial membrane along with the electron transport chain.

Its network of membrane tubes and sheets forms channels that carry materials, especially proteins, between parts of the cytoplasm and the nucleus.

Common fertilisers supply nitrogen, phosphorus and potassium (NPK); iron is a micronutrient that is usually not part of them. Plants need nitrogen, phosphorus and potassium in large amounts, so these are called primary macronutrients, and fertilisers such as urea, DAP, MOP and NPK mixtures are made to supply them.

Bauxite, a hydrated aluminium oxide (Al₂O₃·2H₂O), is the main ore from which aluminium is extracted. Bauxite is first purified into alumina (aluminium oxide) by the Bayer process.

A guard tube is filled with anhydrous calcium chloride, which absorbs moisture and keeps the hydrogen chloride gas dry. In the school experiment, hydrogen chloride gas is made by heating sodium chloride with concentrated sulphuric acid, and the gas is passed through a guard tube containing calcium chloride.

Red, green and blue are the primary colours of light because mixing them in different proportions produces all other colours.

An alkali is a base that dissolves in water, so all alkalis are soluble, but not all bases are alkalis; statement 1 has it the wrong way round.

The stinging hairs on nettle leaves inject methanoic acid, also called formic acid, into the skin, which causes the burning pain.

When red and green light are added together, the eye sees yellow. Red, green and blue are the primary colours of light.

A plane mirror forms an image behind the mirror where light only seems to come from, with left and right swapped.

This is the order in which these metals stand in the reactivity series, and it matches how vigorously they release hydrogen from dilute hydrochloric acid.

Acceleration is the change in velocity divided by the time taken, and 10 minutes is one-sixth of an hour.