CHAPTER 7 ENERGY CHANGES

Question 1

What is an exothermic reaction

Answer 1

One that gives out heat energy to the surroundings so the temprature of the surroundings increases

Question 2

What is an endothermic reaction

Answer 2

One that takes in energy from the surroundings so the temprature of the surroundings decreases

Question 3

Endothermic reactions include

Answer 3

Thermal decomposistion
Electrolysis
Acid + hydrogen carbonate
Photosynthesis

Question 4

Energy diagram questons
X axis?
Y axis?
What do you have on the two flat lines?
What is the bigger line going to top of curve?
What is the line between two flat lines?

Answer 4

1-progress of reaction
2-energy
3-products and reactants
4.-activation energy
5.- energy change

Question 5

What does making and breaking bonds do

Answer 5

Release energy

Question 6

What does the overall energy change =

Answer 6

Energy used to break bonds - energy released on making new bonds

Question 7

What type of reaction is it if there is more energy released on making new bonds than energy used breaking bonds

Answer 7

Exothermic and overall energy change is negative

Question 8

What type of reaction is it if there is more energy required to break the bonds than making new ones

Answer 8

Endothermic and overall energy change would be positive

Question 9

How to find overall energy change bigger question

Answer 9

Reactants
X no of bonds by bond energy(will be given) plus to to other reactant who did the same thing
Then do same thing with reactants
Then must minus reactants then products for example 629 - 732 = -103

Question 10

Aim of temprature rise rp

Answer 10

To investigate how changing the mass of zinc affects the temprature rise in this reaction

Question 11

Method step by step of temprature rise rp

Answer 11

1.-Use a measuring cylinder to put 25 cm3 of 1.0 mol/dm3 copper sulfate solution into a
polystyrene cup.

2.-Weigh out 0.5 g of zinc powder in a weighing boat – remember to set weighing scale to zero when adding zinc

3.-Record the temperature of the copper thermometer sulfate solution in a suitable table.

4.-Now tip the zinc into the copper sulfate solution, put the lid on the cup and stir well with the thermometer. Enclose the thermometer in the hole in the lid

5.-Keep stirring until the temperature reaches a maximum. Record the highest temperature and find the temperature rise.

6.-Empty the polystyrene or use another polysstyerne cup. If you use the same one You may need to rinse further

7.-You are going to repeat this with 1.0, 1.5, 2.0 and 2.5 g of zinc.