C6 - Energy changes in chemical reactions

Question 1

In chemical reactions energy cannot be

Answer 1

created or destroyed only transferred

Question 2

Depending on energy transfer chemical reactions are either

Answer 2

exothermic or endothermic

Question 3

Exothermic reactions get

Answer 3

hotter as energy from reacting chemicals is transferred to the surrounding which increases temperature. The energy given out can be used to keep the reaction going so they don’t stop until they run out of reactants.

Question 4

examples of exothermic reactions

Answer 4

Combustion of fuels
Acid-base neutralization
Displacement reactions
Respiration in cells

Question 5

Endothermic reactions

Answer 5

get colder as the energy from surroundings are transferred to reacting chemicals causing temperature of surroundings to decrease. Endothermic reactions need a constant energy supply to keep the reaction going.

Question 6

examples of endothermic reactions

Answer 6

Thermal decomposition
Photosynthesis
Cooking

Question 7

In exothermic reactions chemical energy stored in reactants gets converted to heat energy so

Answer 7

the products have less chemical energy than the reactants and the difference is the heat released.

Question 8

In endothermic reactions heat energy gets converted to chemical energy so

Answer 8

the products have more chemical energy than the reactants.

Question 9

2 requirements for a reaction to take place successfully

Answer 9

1. reacting particles must collide

2. collisions must have more than enough activation energy

Question 10

A molecule of ethane and a molecule of iodine react. What needs to happen for the reaction to occur.

Answer 10

The ethane and iodine molecules must collide.

They must collide with more energy than the activation energy.