OCR GCSE Combined Science B key terms

An unspecialised cell that can divide to produce more stem cells and differentiate into specialised cells.

A mesh tube placed inside an artery to help keep it open.

A transformer that decreases the output potential difference compared with the input potential difference.

A transformer that increases the output potential difference compared with the input potential difference.

Free from living microorganisms.

A surgical contraceptive method that blocks or cuts the sperm ducts or oviducts and is intended to be permanent.

The resistance of a material to bending or changing shape under an applied force.

A change in conditions that can be detected by a receptor.

The relative amounts, in moles, of reactants and products in a chemical reaction, represented by the coefficients in its balanced equation.

A small pore in the plant epidermis, usually on a leaf, whose opening is controlled by two guard cells.

Pores in the surface of a leaf through which gases, including carbon dioxide and oxygen, diffuse.

The total distance a vehicle travels during thinking and braking: stopping distance = thinking distance + braking distance.

The ability of a material to resist breaking under an applied force.

An acid that is completely ionised in aqueous solution.

A structure within a cell, such as a nucleus, mitochondrion or ribosome.

The variable isolated on one side of an equation, expressed in terms of the other quantities.

The change of state directly from solid to gas, without becoming a liquid.

A small number written after an element symbol in a chemical formula, showing how many atoms of that element are represented. An omitted subscript means one.

Replacing a variable in an expression or equation with its numerical value.

A substance used in a reaction; in a yeast respiration investigation, this can be the sugar supplied to the yeast.

A collision between reacting particles that results in a reaction because it has sufficient energy.

A gas, SO₂, produced when sulfur impurities in fuels burn in oxygen.

The total area of all the outside faces or surfaces of a three-dimensional object.

The surface area of an object divided by its volume. Smaller pieces of the same solid have a larger surface area to volume ratio.

A comparison of the surface area available for exchange with the volume that must be supplied: $\text{surface area}:\text{volume}$.

Everything outside the reacting chemical system that can exchange energy with it, including the surrounding solution, container and air.

A junction between neurones, with a small gap across which neurotransmitters carry the signal.