C7 Energy Changes

Question 1

What is the word that describes a reaction that takes in energy

Answer 1

Endothermic

Question 2

What is the word that describes a reaction that takes out energy

Answer 2

Exothermic

Question 3

Three examples of exothermic reactions

Answer 3

Neutralisation. Displacement. Combustion.

Question 4

Three examples of endothermic reactions

Answer 4

Thermal decomposition. Electrolisis. Acid+Hydrogen Carbonate

Question 5

Explain the experiment of measuring energy transfer in simple terms

Answer 5

Measure the initial temperature of the reagents, mix them in a polystyrene cup and measure the temperature of the solution at the end of the reaction to find how much energy has been transferred either in or out the reagents.

Question 6

How can you control the amount of energy lost to the surroundings when measuring energy trabsfer in a polystyrene cup

Answer 6

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

Question 7

Describe what an exothermic reaction looks like through a reaction profile

Answer 7

The products are at a lower energy than the reactants as the reaction has released energy. There is a loop which goes up at first then goes down below the reactants. The loop goes up at first because this is the amount of energy needed to start the reaction called activation energy.

Question 8

What is the activation energy

Answer 8

The minimum amount of energy the reactants need to collide with eachtoher and react

Question 9

What does a difference in height in a reaction profile show

Answer 9

The overall energy change dueing the reaction

Question 10

Describe what a endothermic reaction looks like through a reaction profile

Answer 10

The products are at a higher energy than the reactants. The loop goes much higher than the reactants which are at the bottom of the graph and then loops slightly at the end which is where fhe products lay.

Question 11

What type of reaction is bond breaking, why

Answer 11

Endothermic reaction, the enrgy used to break the bonds is greater than the energy released by forming them

Question 12

What type of reaction is bond forming, why

Answer 12

Exothermic reaction, the energy released by forming bonds is greater than the energy used to break them

Question 13

What is the overall energy change

Answer 13

The sum of energies needed to bresk bonds in the reactant - the energy released when the new bonds are formed in the products