chemistry topic 5-energy changes

Question 1

how is energy moved around?

Answer 1

in chemical reactions

Question 2

if the products of a reaction store more energy then a reactant what ha happened?

Answer 2

they have taken in energy

Question 3

what happens in an exothermic reaction?

Answer 3

energy is transferred to the surroundings and gives out heat

Question 4

what are everyday uses of exothermic reactions?

Answer 4

-hand warmers
-self heating cans

Question 5

what happens in an endothermic reaction?

Answer 5

heat / energy is taken in

Question 6

how is an endothermic reaction shown?

Answer 6

a fall in temperature

Question 7

what is an everyday use of an endothermic reaction?

Answer 7

-sports injury packs

Question 8

what do reaction profiles show?

Answer 8

energy changes

Question 9

what is activation energy shown?

Answer 9

minimum amount of energy reactants need to collide and react

Question 10

how can you measure the amount of energy released by a chemical?

Answer 10

1. take temperature of reagents
2. mix them in a polystyrene cup
3. measure temperature at the end of the reaction and calculate the difference

Question 11

what does the difference in height in a reaction profile show?

Answer 11

the overall energy change during the reaction

Question 12

what happens during a chemical reaction to bonds?

Answer 12

old bonds broken and new bonds are made

Question 13

is bond breaking exothermic or endothermic?

Answer 13

endothermic

Question 14

is bond forming endothermic or exothermic?

Answer 14

exothermic

Question 15

what is the equation for overall energy change?

Answer 15

energy to _ energy released
break bonds forming bonds

Question 16

what do chemical reactions in a cell produce?

Answer 16

electricity

Question 17

what is and electrochemical cell?

Answer 17

a basic system made up of two different electrodes in contact with an electrolyte

Question 18

why cant some chemical reactions be reversed?

Answer 18

the reacting particles get used up and turned into the products of the reaction

Question 19

what do fuel cells use?

Answer 19

they use fuel and oxygen to to produce electrical energy

Question 20

what are fuel cells?

Answer 20

an electrical cell that is supplied with a fuel and oxygen and uses energy from the reaction between them to produce electrical energy efficiently

Question 21

why are electric batteries not as clean as hydrogen-oxygen cells?

Answer 21

they are made of highly toxic metal compounds