7. Chemical Reactions (with IGCSE objectives) Incomplete

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7. Chemical reactions

7.1 Rate (speed) of reaction


·      Describe the effect of concentration, particle size, catalysts (including enzymes) and temperature on the rate (speed) of reactions.



·      Describe a practical method for investigating the rate (speed) of a reaction involving gas evolution.



·      Describe the application of the above factors to the danger of explosive combustion with fine powders (e.g. flour mills) and gases (e.g. mines).



Note: Candidates should be encouraged to use the term rate rather than speed.







·      Devise a suitable method for investigating the effect of a given variable on the rate (speed) of a reaction.


·      Interpret data obtained from experiments concerned with rate (speed) of reaction.


·      Describe and explain the effects of temperature and concentration in terms of collisions between reacting particles.



·      Describe the role of light in photochemical reactions and the effect of light on the rate (speed) of these reactions.



·      Describe the use of silver salts in photography as a process of reduction of silver ions to silver; and photosynthesis as the reaction between carbon dioxide and water in the presence of chlorophyll and sunlight (energy) to produce glucose and oxygen.














7.2 Reversible reactions


·      Describe the idea that some chemical reactions can be reversed by changing the reaction conditions.

Limited to the effects ofheat on hydrated salts, including hydrated copper (II) sulfate and hydrated cobalt(II) chloride.


CuSO4.5H2O(s) <---> CuSO4(s) + 5H2O(l)


When you heat blue crystals of copper (II) sulphate, they break down into anhydrous (no water) copper (II) sulphate, a white powder.

It releases energy so it’s endothermic.

The reaction is easy to reverse by adding water; the


Marta Paiva de Sousa


Incomplete chapter 7

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