Basic Chemistry for Rusty Scientists

Matter Stuff solids liquids gases

Energy Most text definitions are along the lines of: Energy is the ability to do work!??????? Energy causes change??? The fact is, no one can simply define what Energy is! Really! Energy is a property or characteristic (or trait or aspect?) of matter that makes things happen, or, in the case of stored or potential energy, has the "potential" to make things happen.

Atoms Atoms : the characteristic particle of an element and the basic building block of all matter.

Molecules Molecules: the fundamental unit of an element or compound.

Elements Pure substances composed of only one type of particle ie atoms. There are about 90 naturally occurring elements. T Lereh Periodic table

Elements

Compounds Pure substances composed of 2 or more elements

Some molecules of compounds

Mixtures Substances composed of a variety of elements and/or compounds

Two significant mixtures The Air: – nitrogen – oxygen – carbon dioxide – nitrous oxide – sulphur dioxide – etc, etc Sea Water: water oxygen carbon dioxide sodium chloride magnesium chloride sodium sulphate etc, etc e

Covalent bonding Shared outer electrons shared equally Shared outer electrons shared un equally results in a polar molecule

Ionic bonding Some atoms tend to gain electrons from other atoms gaining a slight –ve charge - negative ions Other atoms tend to lose electrons to other atoms losing a slight –ve charge results in a – positive ions

Water is a polar molecule

Bonds between hydrogen and oxygen within the one molecule are polar covalent bonds Bonds between hydrogen of one molecule and oxygen of another molecule due to the difference of electrical charge are called hydrogen bonds.

Because of its polarity and wedge shape water molecules are particularly good at breaking up the ionic bonds of many substances