Chemistry Glossary

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A

  • Atom and Molecule: difference

Atomol.jpg

Atoms are the smallest part of an element that can take part in a chemical reaction; molecules are the smallest particle of either an element or compound that can exist independently and at the same time keep the properties of the original substance, e.g. the smallest unit of water is the water molecule, which i made up of two atoms of hydrogen and one of oxygen

  • Avogadro's Number (Symbol: NA )

This is the number of entities (atoms, molecules, etc ) in one Mole of a substance.
One NA is currently taken as being 6.022 ×1023 per mole


B


C

  • Chemical bonds

There are two main types of chemical bonding, covalent and ionic, and two more specialised types, metallic and hydrogen bonding

Many chemicals have a characteristic colour and this can help with it's classification or analysis. A special analytical tool that uses colour to determine a chemical, or measure a rate of reaction is called a Spectrometer

  • Chemical matter

Three types, compound, mixture or element.

  • Chemistry

Chemistry is the scientific study of substances.


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I

  • Isotopes

Atoms of a given element which have the same number of protons and electrons and the same chemical properties, but have a different number of neutrons in their nuclei, and consequently different atomic masses. Isotopes may be either stable or radioactive.


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M

  • Mass

Mass is the amount of substance of an object or body. It is measured in grams (or its multiples.)


N


O

  • Organic compounds

All compounds that contain carbon. All other compounds are inorganic


P

  • PH a measure of the acidity or alkalinity of a solution.
  • Polymers

Cellulose molecule which is a natural Polymer

Polymers are long--chain molecules in which a group of atoms are prepeated. They can be natural e., cellulose, DNA, fats, proteins and starches - or they can be artificial eg., nylon, polystyrene, polthene, PVC and in fact all by products of plastics


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R

This is a measure of how much the path of a ray of light is bent when moving from one medium it is passing through, to another. This is very important in chemistry, as an analytical tool, as some chemicals are Optically active


S

  • States of matter

Solid, liquid or gas

  • Sub-atomic particles

Chemical properties of elements depend on the structure of their atoms which are made up of three sub-atomic particles. Protons, which are positively charged, neutrons (neutral-no charge) and electrons which are negatively charged. Protons and neutrons are situated in the nucleus of the atom and the elctrons orbit the nucleus. The number of protons in the nucleus of the element determines the atomic number used in the periodic table.

  • Sublimation

Occurs when chemical matter changes directly from the solid to a gas without first melting into a liquid. Iodine is an example.


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V

  • Valency

Propery of atoms or groups, equal to the number of atoms of hydrogen that the atom or group will combine with or displace in forming compounds


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