A-Z Chemistry definitions for use with A-Level Chemistry

Our database of chemistry definitions provides key information and a summary of many chemistry terms, covering them in enough detail to help you fully understand the terms in preparation for your A-Level Chemistry exams.

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Crystals

Key Information & Summary Crystals are solids in which all of the atoms are arranged in repeating patterns There are 4 types of crystals: metallic, ionic, covalent, and molecular Metallic crystals have metallic bonds Ionic crystals have ionic bonds Covalent crystals have covalent bonds Molecular crystals are held together through intermolecular forces, such as hydrogen ...

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Confidence Limits

Key Information & Summary Confidence limits show how accurate an estimation of the mean is, or is likely to be Confidence intervals show the range in which the true value is likely to fall within Confidence intervals are based on the point estimate, the confidence level required, and the standard error of the point estimate ...

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Conduction

Key Information & Summary Conduction is the transfer of energy from one atom to another through direct contact There are three main types of conduction: ionic conduction, electric conduction, and thermal conduction Solids are the most efficient conductors, with gases being the worst – this is because the particles are much closer together What is ...

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Compound

Key Information & Summary A compound is a substance which is formed from identical molecules made of more than one element which are bonded together Compounds are the result of a chemical reaction and always have a unique chemical composition The quantity of each element in a compound has a fixed ratio Mixtures are not ...

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Complex (Coordination Complex)

Key Information & Summary A complex is a central metal atom bonded to other molecules (called ligands) through dative covalent bonds The number of atoms bonded to the central metal atom is called the coordination number Ligands can be classified as monodentate, bidentate, and polydentate Complexes have very specific naming conventions What is a complex? ...

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Chromatography

Key Information & Summary Chromatography is a technique used to separate mixtures The mixture to be separated is dissolved in a fluid called the mobile phase. This helps to carry the mixture through a stationary phase. Compounds are separated because they will move through the stationary phase at different speeds The main types are thin-layer ...

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Chemical Species

Key Information & Summary A chemical species is a set of molecular entities which are chemically identical and can explore the same molecular energy levels at a set timescale If two conformational isomers interconvert slowly enough to each be detected by different NMR spectra, they would be defined as two different chemical species In supramolecular ...

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Electric Charge

Key Information & Summary Electric charge is a physical property of matter which causes objects to experience a force when it is placed in an electric field Protons carry a positive charge and electrons carry a negative charge An ion is an atom that has either gained or lost electrons Coulombs are the units of ...

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Catalyst

Key Information & Summary A catalyst is a substance which increases the rate of a reaction without being used up itself. They provide an alternative reaction route with a lower activation energy. Catalysts are split into two main types: heterogeneous and homogeneous Autocatalysis is a reaction which can accelerate itself, as one of the products ...

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Calibration

Key Information & Summary Calibration is the act of ensuring that a scientific process or instrument will produce accurate results every time An instrument needs to be properly calibrated before it is used to make sure you obtain accurate results There are two main methods of calibration: the working curve method and the standard addition ...

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