# Energy Changes and Measuring Temperature

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• Created by: joshd
• Created on: 01-04-14 20:43
What does a graph that shows an exothermic reaction show?
The products are at a lower energy than the reactants. The difference in height represents the energy given out in the reaction. The initial rise in the line represents the energy needed to break the old bonds.
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What does a graph that shows an endothermic reaction show?
The products are at a higher energy than the reactants. The difference in height represents the energy taken in during the reaction.
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How can you measure temperature changes? (4 reactions) (1)
-Dissolving salts in water - Neutralisation reactions (where an acid and base react together)
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How can you measure temperature changes? (4 reactions) (2)
-Displacement reactions (where a more reactive element takes the place of a less reactive element). -Precipitation reactions (where two solutions react to produce an insoluble precipitate)
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How can you measure the amount of energy produced by a chemical reaction in solution?
By taking the temperature of the reactants (making sure they're the same), mixing them in a polystyrene cup and measuring the temperature of the solution at the end of the reaction.
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What is the biggest problem with temperature measurements?
The amount of heat lost to the surroundings.
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How can you reduce the loss of heat a bit?
By putting the polystyrene cup into a beaker of cotton wool to give more insulation, and putting a lid on the cup to reduce energy lost by evaporation.
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Describe the method of the example of neutralising hydrochloric acid with sodium hydroxide. (1)
1 Add 25cm3 of dilute hydrochloric acid to a polystyrene cup, and record the temperature of the acid. 2 Put 25cm3 of dilute sodium hydroxide in a measuring cylinder and record its temperature.
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Describe the method of the example of neutralising hydrochloric acid with sodium hydroxide. (2)
3 Making sure they're the same temperature, add the alkali to the acid and stir. 4 Take the temperature of the mixture every 30 seconds, and record the highest temperature it reaches.
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## Other cards in this set

### Card 2

#### Front

What does a graph that shows an endothermic reaction show?

#### Back

The products are at a higher energy than the reactants. The difference in height represents the energy taken in during the reaction.

### Card 3

#### Front

How can you measure temperature changes? (4 reactions) (1)

### Card 4

#### Front

How can you measure temperature changes? (4 reactions) (2)

### Card 5

#### Front

How can you measure the amount of energy produced by a chemical reaction in solution?