Punjab PSEB Matric Science key terms

A substance that produces hydrogen ions (H⁺) when dissolved in water, tastes sour, turns blue litmus red, and reacts with a base to give salt and water.

A substance that produces hydroxide ions (OH⁻) in water, feels soapy, turns red litmus blue, and neutralises an acid to form salt and water.

A dye or mixture whose colour changes when the acidity or alkalinity of a solution changes; litmus, methyl orange and phenolphthalein are common examples used in school laboratories.

The reaction between an acid and a base in which they cancel each other's effect, always producing a salt and water; the heat released makes it exothermic.

A list of metals arranged in decreasing order of their tendency to lose electrons and form positive ions, used to predict displacement reactions and the extraction of metals from ores.

A uniform mixture of a metal with one or more other elements, made to improve hardness, strength or resistance to corrosion; brass and steel are everyday examples.

A family of carbon compounds having the same functional group and similar chemical properties, in which successive members differ by one CH₂ unit, for example the alkanes.

An atom or group of atoms attached to a carbon chain that gives the compound its characteristic chemical reactions, such as –OH in alcohols or –COOH in carboxylic acids.

The process by which green plants use sunlight, water and carbon dioxide, in the presence of chlorophyll, to make glucose and release oxygen.

The breakdown of food inside living cells to release energy, with oxygen (aerobic) or without it (anaerobic), giving carbon dioxide and water as the usual end products.

Tiny openings on the surface of leaves, guarded by two guard cells, through which carbon dioxide enters and oxygen and water vapour leave the plant.

The plant tissue made of hollow, dead tubes that carries water and dissolved minerals from the roots upward to the leaves.

The plant tissue with living conducting cells that transports food made in the leaves, mainly sucrose, to growing parts and storage organs.

A quick, automatic response to a stimulus that does not need conscious thought, such as withdrawing the hand from a hot object; it is coordinated by the spinal cord.

A chemical messenger released by a gland or a plant cell that travels in the blood or sap and controls growth, metabolism or reproduction.

The transfer of pollen grains from the anther of a flower to the stigma of the same or another flower, brought about by wind, water or animals.

The passing on of characters from parents to offspring through genes carried on chromosomes, which is why children resemble their parents.

The slow, gradual change in the inherited characters of a population over many generations, brought about by natural selection and producing new species from earlier ones.

The bouncing back of light when it strikes a polished surface, following the laws that the angle of incidence equals the angle of reflection and all rays lie in one plane.

The bending of light as it passes from one transparent medium into another of different optical density, caused by a change in the speed of light.

The ratio of the speed of light in vacuum to its speed in a given medium; a larger value means the medium bends light more strongly.

The point on the principal axis where rays parallel to the axis meet after reflection from a concave mirror or refraction through a convex lens.

The ability of the eye's ciliary muscles to change the focal length of the lens so that objects at different distances are focused clearly on the retina.

Short-sightedness, in which a person sees nearby objects clearly but distant ones blurred because the image forms in front of the retina; corrected with a concave lens.

The splitting of white light into its component colours when it passes through a prism or water drop, because different colours bend by different amounts.

The rate of flow of electric charge through a conductor, measured in amperes; one ampere is one coulomb of charge passing a point each second.

At constant temperature, the current through a metallic conductor is directly proportional to the potential difference across its ends, so V = IR.

The property of a conductor that opposes the flow of electric current, equal to the potential difference divided by the current and measured in ohms.

The rate at which electrical energy is consumed or delivered in a circuit, equal to voltage multiplied by current, and measured in watts.

The region around a magnet or a current-carrying wire where a magnetic force can be detected, shown by field lines running from north to south outside a magnet.

The production of an electric current in a coil when the magnetic field linked with it changes, the principle behind electric generators and transformers.

All the living organisms of an area together with the non-living surroundings they interact with, such as soil, water and sunlight, forming a self-regulating unit.

A series of organisms in which each one eats the one before it, showing how energy and matter pass from producers to consumers and finally to decomposers.

Each step in a food chain, such as producer, primary consumer or secondary consumer; only about ten per cent of energy passes to the next level.

The increase in concentration of harmful substances such as pesticides at each higher trophic level, because these chemicals are not broken down or excreted.

A layer of ozone gas in the upper atmosphere that absorbs most of the sun's harmful ultraviolet radiation and protects living things on Earth.

The trapping of heat near Earth's surface by gases such as carbon dioxide and methane, which lets sunlight in but slows the escape of infrared radiation.

Using natural resources in a way that meets present needs without destroying them for future generations, balancing growth with conservation.

Collecting and storing rainwater from roofs or catchments for later use and to recharge groundwater, instead of letting it run off wastefully.