C2b Topic 5 - Chemical Reactions Flashcards Preview

Edexcel Chemistry C2 GCSE > C2b Topic 5 - Chemical Reactions > Flashcards

Flashcards in C2b Topic 5 - Chemical Reactions Deck (21)
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1

Energy is released when new bonds are formed - so bond formation is an _____________ process.

Exothermic!

2

In an EXOTHERMIC reaction, the heat energy released in forming bonds in the products is ___________ than the energy used in breaking old bonds in the reactants.

Greater!

3

An EXOTHERMIC reaction is one which overall

GIVES OUT ENERGY to the surroundings in the form of heat, shown by a RISE IN TEMPERATURE.

4

In an ENDOTHERMIC reaction, the energy required to break old bonds in the reactants is ___________ than the heat energy released when new bonds are formed in the products.

Greater!

5

An ENDOTHERMIC reaction is one which overall

TAKES IN ENERGY from the surroundings in the form of heat, shown by a FALL IN TEMPERATURE.

6

In an EXOTHERMIC reaction, energy is

GIVEN OUT

7

In an ENDOTHERMIC reaction, energy is

TAKEN IN

8

Examples of endothermic reactions

1) Photosynthesis uses light energy from the sun to convert carbon dioxide and water into glucose and oxygen.
2) As ammonium nitrate dissolves in water it takes in heat energy from its surroundings.

9

In an EXOTHERMIC REACTION the products are at a ___________ energy than the reactants

Lower!

10

In an ENDOTHERMIC REACTION the products are at a _____________ energy than the reactants

Higher!

11

Rate of reaction depends on four things

1) Temperature
2) Concentration - (or pressure for gasses)
3) Catalyst
4) Surface area of solid - (or size of particles)

12

A catalyst

Is a substance that changes the speed of a reaction, without being used up in the reaction.

13

A catalyst works by

1) Lowering the activation energy
2) This makes it easier for the reaction to happen and increases the rate of reaction
3) This means that a lower temperature can be used without the rate of reaction dropping

14

Why are catalytic converters used in vehicle exhausts

1) Vehicle exhausts can give off poisonous gases like carbon monoxide if petrol doesn't burn properly.
2) A catalytic converter increases the rate at which carbon monoxide and unburnt fuel in exhaust gases react with oxygen to produce carbon dioxide and water.
3) The catalyst has a large surface area and works best at high temperatures to increase the rate of reaction.

15

More collisions increases the

Rate of reaction!

16

Higher temperature increases

Collisions!

17

Higher concentration of pressure increases

Collisions!

18

Larger surface area increases

Collisions!

19

Catalyst increases the number of

SUCCESSFUL collisions!

20

Faster collisions increase the

Rate of reaction! you can only do this by increasing the temperature.

21

Energy must be supplied to break existing bonds - so breaking bonds is an ______________ process.

Endothermic!