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AQA Chemistry Unit 2 ­ Key Points
1.1 Chemical bonding
Elements react together to form compounds by gaining or losing electrons or by sharing
The elements in Group 1 react with the elements in Group 7. As they react, atoms of Group
1 elements can each…

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2.3 Giant covalent structures
Some covalently bonded substances
have giant structures. These substances have high melting points and boiling points.
Graphite contains giant layers of covalently bonded carbon atoms. However, there are no
covalent bonds between the layers. This means they can slide over each other, making
graphite soft and…

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We can calculate empirical formulae given the masses or percentage composition of elements
present. (higher)

3.4 Equations and calculations
Balanced symbol equations tell us the number of moles of substances involved in a chemical
We can use balanced symbol equations to calculate the masses of reactants and products in…

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4.3 The effect of temperature
Reactions happen more quickly as the temperature increases.
Increasing the temperature increases the rate of reaction because particles collide more
frequently and more energetically. More of the collisions results in a reaction because a
higher proportion of particles have energy greater than the activation energy.…

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An alkali is a soluble hydroxide. Alkalis produce OH- ions when we add them to water.
We can use the pH scale to show how acidic or alkaline a solution is.

5.2 Making salts from metals or bases
When we react an acid with a base a neutralisation reaction occurs.…

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