NECO BECE key terms

The process by which green plants use sunlight, water and carbon dioxide to make food (glucose) in their leaves, releasing oxygen as a by-product. It happens mainly in chloroplasts containing chlorophyll.

The green pigment found in chloroplasts of plant cells that absorbs light energy used to drive photosynthesis. It gives leaves their green colour and is essential for food production in plants.

The chemical breakdown of food substances such as glucose in living cells to release energy, carbon dioxide and water. Aerobic respiration needs oxygen; anaerobic respiration occurs without oxygen.

Tiny openings, mostly on the underside of leaves, through which gases such as carbon dioxide and oxygen enter and leave the plant. Water vapour also escapes through them during transpiration.

The loss of water vapour from plant leaves through the stomata. It helps pull water and dissolved minerals upward from the roots and cools the plant on hot days.

The movement of water molecules through a partially permeable membrane from a region of higher water concentration to a region of lower water concentration. It explains how plant roots absorb water.

The spreading of particles of a substance from a region of higher concentration to a region of lower concentration until they are evenly distributed. It needs no energy and occurs in gases and liquids.

The smallest living unit of a living organism. It has a cell membrane and cytoplasm, and may contain a nucleus and other structures that carry out specific life functions.

The removal of waste products of metabolism from the body, such as carbon dioxide through the lungs and urea through the kidneys. It is different from egestion, which removes undigested food.

A bean-shaped organ that filters waste substances such as urea and excess salts and water from the blood, forming urine. Humans normally have two kidneys located in the lower abdomen.

The smallest particle of an element that can take part in a chemical reaction. It consists of a nucleus containing protons and neutrons, surrounded by electrons in shells.

The smallest particle of a substance that can exist on its own, made of two or more atoms chemically joined together. Water, for example, has molecules made of two hydrogen atoms and one oxygen atom.

A pure substance made of only one kind of atom that cannot be split into simpler substances by chemical means. Common examples are oxygen, iron, carbon and sodium.

A pure substance formed when two or more different elements are chemically combined in fixed proportions. Water and common salt are compounds, and their properties differ from those of their elements.

A combination of two or more substances that are not chemically joined, so each keeps its own properties. Mixtures can usually be separated by physical methods such as filtration or evaporation.

A method of separating a solid from a liquid by passing the mixture through a filter paper or other porous material. The solid is trapped as residue while the liquid passes through as filtrate.

The change of a liquid into vapour at the surface, taking place below its boiling point. It is used to recover dissolved solids from a solution by boiling off the liquid.

A substance that contains hydrogen ions and turns blue litmus paper red. Acids react with bases to form salt and water, and with some metals to release hydrogen gas.

A substance that reacts with an acid to form salt and water only, and turns red litmus paper blue. Soluble bases such as sodium hydroxide are called alkalis.

A scale from 0 to 14 that measures how acidic or alkaline a solution is. Values below 7 show acidity, 7 is neutral, and values above 7 show alkalinity.

A push or pull that can change the speed, direction or shape of an object. Force is measured in newtons, and friction, gravity and magnetism are common examples.

The force that opposes motion when two surfaces are in contact and slide against each other. It produces heat, can slow moving objects, and may be reduced by using lubricants.

The force of attraction between objects that have mass, pulling them toward each other. It gives objects weight and makes them fall toward the ground when dropped.

The force with which gravity pulls an object toward the earth, measured in newtons. It changes with the strength of gravity, unlike mass, which stays the same everywhere.

The quantity of matter contained in an object, measured in kilograms or grams. It does not change with location and is different from weight, which depends on gravity.

The mass of a substance per unit volume, often expressed in grams per cubic centimetre. Objects less dense than water float, while denser objects sink.

The force acting normally on a unit area of a surface, measured in pascals or newtons per square metre. It increases when force increases or when the area is reduced.

The capacity to do work, existing in forms such as kinetic, potential, chemical, heat and electrical energy. Energy cannot be created or destroyed but can change from one form to another.

The rate at which work is done or energy is transferred, measured in watts. One watt equals one joule of energy used per second.

A word that names a person, animal, place, thing or idea, such as teacher, goat, Lagos or honesty. Nouns can be common or proper, countable or uncountable, and singular or plural.

A word used in place of a noun to avoid repeating it, such as he, she, it, they, who or themselves. The noun it refers to is called its antecedent.

A word that describes or gives more information about a noun or pronoun, such as tall, three or beautiful. Adjectives usually come before the noun or after a linking verb.

A word that modifies a verb, adjective or another adverb, often telling how, when or where something happens, such as quickly, yesterday or here. Many adverbs end in -ly.

A word that expresses an action, occurrence or state of being, such as run, happen or is. Verbs change form to show tense, number and person in a sentence.

The form of a verb that shows the time an action takes place: past, present or future. For example, walked is past, walk is present and will walk is future.

Agreement between words in a sentence, especially between a subject and its verb in number and person. For example, the boy runs but the boys run.

A figure of speech that compares two different things using the words like or as, such as as brave as a lion. It makes description vivid and clear.

A figure of speech that describes one thing as if it were another, without using like or as, such as the classroom was a zoo. It creates vivid comparison.