OCR GCSE Combined Science B key terms

A temperature-sensitive resistor whose resistance decreases as its temperature increases. NTC means negative temperature coefficient.

A model in which an atom has a tiny, positively charged central nucleus containing most of its mass, surrounded by electrons.

Particles or electromagnetic waves emitted from an atomic nucleus.

A small molecular unit that joins with other nucleotides to form a DNA strand.

The tiny central region of an atom, containing protons and neutrons and almost all the atom’s mass.

The lens closest to the specimen, which provides the first stage of magnification.

A hormone produced by the ovaries that rebuilds the uterus lining, inhibits FSH release and, at a high level before ovulation, stimulates LH release.

A component whose current is directly proportional to the potential difference across it when its temperature is constant.

The temperature or pH at which a particular enzyme works fastest.

The temperature at which a process has its highest rate under the conditions being investigated.

The approximate scale of a quantity expressed as a power of ten, rather than an exact measurement.

A rock containing enough of a useful metal or metal compound for extraction to be economically worthwhile.

A carbon-based compound. Most organic compounds contain carbon bonded to hydrogen; some simple carbon compounds, such as carbon dioxide, are classified as inorganic.

A single living thing.

A repeated change or movement back and forth about a central position or value.

The net movement of water molecules through a partially permeable membrane from a more dilute solution to a more concentrated solution.

The occupied electron shell furthest from the nucleus. Its electrons are involved in chemical bonding.

The release of gases from inside the Earth, including through volcanic activity.

A result that is unusually different from other results or from the general pattern; also called an anomalous result.

The release of a mature egg from an ovary.

Loss of electrons by a chemical species.

Gases including nitrogen monoxide, NO, and nitrogen dioxide, NO₂. They form when nitrogen is oxidised at high temperatures and the products undergo further oxidation in air.

A gas whose molecules contain three oxygen atoms, $\mathrm{O_3}$. Ozone in the atmosphere absorbs ultraviolet radiation and helps protect life on Earth.

A medicine that reduces pain without removing the underlying cause of the disease.

An error caused by viewing an object, pointer or liquid level at an angle to its scale.

A circuit with separate branches connected between the same two points, allowing current to divide between branches.

The original unstable nucleus that undergoes radioactive decay.