W

Water vapour     This is water in the form of a gas. Although there is a technical difference between a vapour and a gas but that does not matter at GCSE. When a kettle is boiling, many people call the white clouds "steam". This is not correct.  The true steam is the invisible gas that is right by the mouth of the kettle. The white clouds are actually made of droplets of liquid water that have condensed as the steam met the cooler air.

The scalds from steam are much worse than scalds from liquid water because the energy released as the gas turns into liquid is added to the energy released as a hot substance becomes cooler.

Weathered     Rocks that have been worn away are said to have been weathered. This does not have to be because of the weather! The action of roots, people walking  etc are all weathering justb as much as the effect of wind-borne grit and acid rain.

Weathering     The breakdown of rocks. This does not include the deliberate extraction by mining or quarrying.

Word equation     A way to record the changes that have taken place in a chemical equation. If a word equation is asked for, be careful to use the correct words (eg do you mean chlorine or chloride, sulphide or sulphate etc). Make sure that you include all the substances. Do not use "=" (which would mean that the substances are the same but rather use an arrow to show that the substances have changed.

Some examinations will penalise you if you use a chemical equation (symbols) when they ask for a word equation. Apart from failing to do what you are asked, it is also more difficult to write a correct chemical equation. Sometimes the examiner will allow a perfectly correct chemical equation but penalise anything that is not absolutely right.

As usual, read the question carefully to  make sure that you are answering the question that has been set rather than the answer you WISH had been set.

MORE WORDS AND DEFINITIONS WILL BE ADDED.

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