Lesson 1

• Element: A pure substance that is made up of only one type of atom, e.g., carbon, hydrogen, oxygen
• Compound: A substance that is formed when atoms of two or more different elements are chemically joined together in a definite ratio, e.g., sodium chloride (NaCl - common salt)
• Mixture: In mixtures, different kinds of particles are simply mixed together. For example, Yaqona is a mixture of kava and water and likewise tea is a mixture of tea leaves, sugar and water.
• Pure Chemicals: Chemical substances are often called 'pure' to set them apart from mixtures. In a pure chemical, all the particles are the same, e.g. pure water
• A physical change is a change only in appearance, form or state. It does not form any new substance. It is usually reversible. It does not usually release heat e.g. melting of ice.
• A chemical change is any change that results in the formation of a new substance. It is usually irreversible. It often releases heat e.g. burning of magnesium to produce magnesium oxide.
• 1. Sedimentation

  • Is a process in which insoluble particles can be removed from water or any other liquid. For example, when muddy water is stirred and left for a while, the dirt (impurities) in the water gradually settles down at the bottom of the container.
• 2) Decantation

  • Is pouring a solution from a container, leaving sediments (precipitate) in the bottom of the container. For example, once the dirt has settled down, the water can be poured into another container.
• 3) Filtration

  • Is using a filter to remove solid particles from a liquid by causing the liquid to pass through the filter. For example, mixing yaqona is an example of filtration. The cloth traps the solid (kava) and lets the liquid (yaqona) pass through.
• 4) Centrifugation

  • Uses centrifugal force to separate components of a substance. For example, separating dirt particles from clothes in a washing machine.