TWC 0.04 – Recap

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  • Atoms can join together as molecules by forming covalent bonds.
  • Covalent bonds are formed when atoms share an electron.
  • Another way for atoms to bond is through ionic bonding.
  • Ionic bonding occurs when one atom steals an electron from another atom.
  • Electrons have a negative charge, so when one is stolen, the thieving atom acquires a negative charge and is called an anion.
  • The atom that is stolen from acquires a positive charge and is called a cation.
  • Rainfall encounters carbon dioxide and dissolves it, which makes the water acidic.
  • Acidic water is able to dissolve mineral salts as it percolates through the bedrock.
  • Some water is collected from underground aquifers — this kind of water usually contains a high amount of dissolved mineral salts and is referred to as ‘hard water’.
  • Other water is collected from reservoirs — this kind of water usually has a much lower mineral content because it has had less contact with mineral salts. It is referred to as ‘soft water’.


New Words


Polar molecule  A molecule that has an uneven distribution of electrons between the covalently bonded atoms

Cohesion  The measure of how much molecules of the same type are attracted to each other

Adhesion  The measure of how much two substances or surfaces are attracted to each other

Heat capacity  Also known as ‘specific heat’; the amount of heat it takes to raise 1 gram of a substance by 1 degree C without changing its physical state

Hard water  Water that is alkaline and contains a high level of dissolved calcium and magnesium mineral salts


End 0.04

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