Chemical Reactions

• Alkali metal


  A metal element in Group 1 of the periodic table; alkali metals are highly reactive and explode in water; examples include sodium, potassium and lithium
• Aqueous solution


  A mixture in which something is dissolved in water; a solution in which water is the solvent
• Balanced


  Used to describe a chemical equation in which there are equal numbers of atoms of each element on either side of the equation (following the law of conservation of matter)
• Ball-and-stick model


  A physical model or illustration in which atoms are represented by balls and the chemical bonds between them are represented by sticks
• Charge


  A property of matter that explains electricity and electrical forces; a particle can have a positive charge, a negative charge or no charge (neutral)
• Chemical bond


  A strong attractive force that holds atoms together in a molecule or lattice
• Chemical change


  The rearrangement of atoms to form one or more new substances; another name for a chemical reaction
• Chemical equation


  A representation in words, symbols or diagrams of how atoms are rearranged by a chemical reaction
• Chemical formula


  A symbol that describes the chemical composition of a molecule or lattice; for molecules, each element symbol is followed by a subscript giving the number of atoms of that element (though 1 is never written); for lattices, the subscripts give the proportion of elements
• Chemical reaction


  The rearrangement of atoms to form one or more new substances; the number of each type of atom remains the same
• Chemical symbol


  One or two letters used to represent an element; the first letter is upper case and the second letter is lower case; for example, H (hydrogen), Ca (calcium), Na (sodium)
• Coefficient


  A number placed before a formula in a chemical equation to make sure the equation is balanced; not to be confused with a subscript
• Combustion


  A chemical reaction in which a fuel reacts with oxygen and releases heat
• Compound


  A substance containing atoms of two or more elements joined together by chemical bonds
• Dihydrogen monoxide


  The chemical name for water (H2O), because a water molecule contains two (di-) hydrogen atoms bonded to one (mon-) oxygen atom
• Electrical charge


  A property of matter that explains electricity and electrical forces; a particle can have a positive charge, a negative charge or no charge (neutral)
• Electrode


  A piece of metal used to pass an electric current to or from a battery, living thing or other material
• Gauze mat


  A metal wire mesh that is placed on a tripod to support beakers or flasks while they are heated
• Lattice


  A repeating arrangement of atoms in a metal or ions in an ionic compound
• Law of conservation of matter


  The rule that during all chemical reactions the total number of atoms of each element remains the same
• Mixture


  A combination of two or more substances in which no new substances are formed; the components of a mixture can be separated again using physical methods; contrasted with pure substances (elements and compounds)
• Molecule


  A group of atoms bonded together; the smallest unit of many chemical compounds; examples include oxygen (O2) and water (H2O) molecules
• Physical change


  A change in matter that doesn't affect its chemical composition, such as breaking, mixing and changing state
• Pollutant


  A substance released into the environment that causes harm to humans or wildlife
• Product


  A substance formed by a chemical reaction; in a chemical equation, the products are located to the right of the arrow
• Proportion


  The amount of one thing relative to the amount of another thing
• Ratio


  The amount of one thing relative to the amount of another thing; for example, hydrogen combines with oxygen in the ratio of two-to-one (2:1) to form water, H2O
• Reactant


  A substance that reacts to form one or more new substances; in a chemical equation, the reactants are located to the left of the arrow
• Reactive


  Tending to take part in chemical reactions
• Solution


  A type of mixture formed when one substance dissolves in another
• State symbol


  A symbol used in a chemical equation to indicate the state of matter of a substance; for example, solid (s), liquid (l), gas (g) or aqueous solution (aq)
• Structural equation


  A type of chemical equation that shows how the atoms are rearranged; for example, by using a ball-and-stick model
• Subscript


  A small number used within a chemical formula to indicate how many atoms of an element are present; for example, in H2O there are two hydrogen atoms but only one oxygen atom (the 1 is not written); not to be confused with a coefficient
• Symbol equation


  A type of chemical equation that uses chemical formulas to represent the substances involved in a reaction
• Unbalanced


  Used to describe a chemical equation in which there are unequal numbers of atoms of one or more elements on either side of the equation; these equations must be balanced so that they follow the law of conservation of matter
• Word equation


  A type of chemical equation that uses names to represent the substances involved in a reaction
• Physical change


  Usually reversible, does not change chemical formula
• Chemical reaction


  Irreversible, changes chemical formula
• Indications of chemical reaction

  • Heat
  • Production of gas
  • Formation of a precipitate
  • Color change
• Precipitate


  Substance from 2 clear liquids forming 1 solid chunky substance