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Revision of Topic 1- Chemical Reactions

Revision of Topic 1- Chemical Reactions. 1.Identify a chemical reaction by a change in the appearance of a substance:- - a colour change - bubbles forming – a gas being given off - a solid (precipitate) being formed. 2. Identify a chemical reaction by a detectable energy change could be:-

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Revision of Topic 1- Chemical Reactions

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  1. Revision of Topic 1- Chemical Reactions • 1.Identify a chemical reaction by a change in the appearance of a substance:- • - a colour change • - bubbles forming – a gas being given off • - a solid (precipitate) being formed

  2. 2. Identify a chemical reaction by a detectable energy change could be:- • HEAT being given off – EXOTHERMIC • Heat being taken in – ENDOTHERMIC • Sound being produced • Light being produced

  3. 3. State that all chemical reactions involve the formation of one or more new substances. • Chemical reactions are hard to reverse back to starting materials e.g. table salt is made from chlorine a gas and sodium a metal.

  4. 4. Give examples of chemical reactions which occur in our day to day lives. • E.g. 1) eggs frying • 2) wood burning • 3) a firework taking off • 4) cake baking

  5. 5. State that everything is in the world is made from about 100 elements. • Elements are listed in periodic table • They are the simplest substances possible. (Cannot be broken down to anything simpler)

  6. 6. State that each element has a name and a symbol. • Symbols can be just one letter e.g. H for hydrogen. • Symbols can be two letters e.g. Br for Bromine (One uppercase and one lowercase letter).

  7. 7. State that compounds are formed when elements react together. • When 2 or more elements chemically join together we get a compound. • E.g. sodium + chlorine  sodium chloride • Magnesium + iodine  magnesium iodide

  8. 8. State that mixtures occur when two or more substances come together without reacting. • No chemical reaction involved as substances are easy to reverse – can get starting material back again e.g. salt and sand.

  9. 9. State that a solution is formed when a solute dissolves in a solvent. • Solvent – the liquid in which the solute is dissolved e.g. water • Solute – the substances being dissolved e.g. sugar

  10. There are different types of solutions:- • Dilute solutions where there is little solute in the solution compared to the amount of solvent. • Concentrated solutions where there is a lot of solute dissolved in the solvent compared the amount of solvent. • Saturated – where no more solute can be dissolved.

  11. 10. The compounds with the name ending in –ide contain the two elements indicated • e.g. • (I) sodium + sulphur  sodium sulphide • (II) copper + oxygen  copper oxide

  12. Compounds ending –ite or –ate indicates the additional element oxygen. • Compound ending in -ite have fewer oxygens than compounds ending in -ate. • E.g. • Calcium + sulphur + oxygen --> calcium sulphite • Calcium + sulphur + oxygen --> calcium sulphate • In the above example the formula for lead sulphite is CaSO3 • the formula for lead sulphate is CaSO4

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