General Science Previous Year Questions (PYQ) with Answers – Page 22

Radiation carries heat as electromagnetic waves, and these waves travel even through empty space. Heat moves in three ways.

Both carry their own DNA and ribosomes and can make some of their own proteins. Mitochondria, the powerhouses of the cell, and plastids such as chloroplasts each contain a small circular DNA molecule and 70S ribosomes, much like bacteria.

Xylem carries water along with the minerals dissolved in it from the roots up to the stem and leaves. Plants have two kinds of conducting tissue.

Plants need magnesium in fairly large amounts, so it is a macronutrient, not a micronutrient. Plant nutrients are grouped by how much of them a plant needs.

Atomic number 59 is praseodymium, a lanthanide, and the lanthanides and actinides together make up the f-block. A block is named after the sub-shell that the last electron enters.

Pinctada margaritifera is the black lip pearl oyster, a bivalve mollusc of the warm shallow water of the Indo-Pacific, where it fastens itself to coral reefs by strong threads.

Oil does not dissolve in water; it stays as a separate layer or as floating droplets, so the mixture is heterogeneous and the boundary between the two liquids can be seen.

Pisciculture is the rearing of fish in ponds, tanks and other managed waters, the Latin word piscis meaning fish.

Ethyl acetate is an ester, and esters are the family of organic compounds known for a sweet, fruity smell. It is formed when ethanol reacts with acetic acid in the presence of a little concentrated sulphuric acid, a reaction called esterification, and its formula is CH3COOC2H5.

A nuclear reactor splits heavy atoms; it burns no fuel, so it releases no carbon dioxide and needs no equipment to cut such emissions.

In a suspension the particles of the solute are large enough to be seen and do not dissolve; they stay spread through the liquid only while it is stirred and settle to the bottom when it is left standing.

The Golgi apparatus is the main site where glycoproteins and glycolipids are formed. It is a stack of flat, disc-shaped sacs called cisternae, first described by Camillo Golgi in 1898.

In DNA, adenine always pairs with thymine through two hydrogen bonds, and guanine pairs with cytosine through three. This is called complementary base pairing, and it is why one strand of DNA can be used to copy the other.

Electric current is the rate of flow of electric charge, written as I = Q/t, so one ampere flows when one coulomb of charge passes through a cross-section of a conductor in one second.

An iron, toaster, oven, kettle and heater all turn electrical energy into heat when current flows through a coil of high resistance.

A concave lens spreads the light rays slightly before they enter the eye, so the image moves back onto the retina.

Adrenaline is made by the adrenal glands, which sit like caps on top of the two kidneys. It is released in fear, anger or sudden danger, so it is called the "fight or flight" hormone.

Washing soda is sodium carbonate decahydrate: each unit of sodium carbonate holds ten molecules of water of crystallisation. It is made from common salt in steps: baking soda is heated to get anhydrous sodium carbonate, called soda ash, which is then recrystallised from water to give washing soda crystals.

Red has the longest wavelength in visible light, about 700 nm, so the tiny particles of air, fog, smoke and dust scatter it the least.

The reactivity series lists metals from the most reactive to the least reactive, and potassium heads it because it loses its single outer electron most easily.