General Science Previous Year Questions (PYQ) with Answers – Page 88

An emulsion is a colloid in which tiny droplets of one liquid are spread through another liquid with which it does not mix.

Once a satellite is placed in orbit with the right speed, the Earth's gravity keeps it going round without any engine.

A light year is the distance that light travels in empty space in one year, so despite the word "year" it measures length, not time.

When an object is weighed under water, the water pushes up on it with a buoyant force, so it seems lighter than in air; this reduced reading is its apparent weight.

The bulb of a headlight is placed at the principal focus of a concave mirror, so the reflected light leaves as a strong beam of parallel rays that reaches far down the road.

Lactobacillus turns the lactose sugar of milk into lactic acid, which sours the milk and makes it set into curd.

Probiotics are live, helpful microbes taken in food or supplements to improve the balance of bacteria in the gut. The word means "for life", the opposite of antibiotic, "against life".

What looks like a single flower in a sunflower or marigold is really a head made of many tiny flowers, called florets, packed together.

Vitamin K is needed by the liver to make prothrombin and other clotting factors, without which blood does not clot properly.

The juice in the stem of sugarcane is rich in sucrose, the ordinary table sugar we get from it. Sucrose is a disaccharide (C₁₂H₂₂O₁₁) made of one glucose and one fructose unit joined together.

This statement is false: enzymes are mostly proteins, but most proteins are not enzymes. Proteins do many jobs in the body.

Valency is the combining capacity of an atom, and it is decided by the valence electrons it gains, loses or shares to complete its outer shell.

Sulphuric acid has two replaceable hydrogen atoms, so its equivalent mass is 98 ÷ 2 = 49 g, and 49 g in one litre makes exactly one gram-equivalent per litre.

The mass of the solution is 20 g + 180 g = 200 g, and 20 g of salt in 200 g of solution is 10 per cent.

. Cathode rays behave the same whatever gas is in the tube, so the statement that they depend on the gas is not correct.

Chemical reactions involve only the outer, or valence, electrons, so these decide how an element behaves. Atoms combine by losing, gaining or sharing their valence electrons to reach a stable arrangement, usually eight electrons in the outer shell.

Two miscible liquids that form a homogeneous mixture are separated by distillation, which uses the difference in their boiling points.

A compound microscope magnifies more when both its lenses have short focal lengths. In a compound microscope the objective forms a real, enlarged image, and the eyepiece magnifies it further like a simple magnifier.

The field inside a long solenoid is directly proportional to the number of turns per unit length, so doubling n doubles the field.

The two ends of a diameter split the ring into two equal halves of 10 Ω each, and these two halves are connected in parallel.