Heat energy changes in chemical reactions

Question 1

describe the
-heat energy
-the temperature of the reaction mixture
for endothermic reactions?

Answer 1

-heat energy taken in
-temperature of reaction mixture decreases

Question 2

describe the
-heat energy
-the temperature of the reaction mixture
for exothermic reactions?

Answer 2

-heat energy given out
-temperature of reaction mixture increases

Question 3

which process breaks and forms bonds?

Answer 3

exothermic: bond breaking
endothermic: bond forming

Question 4

Describe how you can see from a reaction profile that a reaction is exothermic. (3)

Answer 4

• energy change is negative.
  -because the products have less energy than the reactants
  -arrow showing the overall change in energy points downwards.

Question 5

Describe how you can see from a reaction profile that a reaction is endothermic.(3)

Answer 5

• energy change is positive.
  -because the products have more energy than the reactants
  -arrow showing the overall change in energy points upwards.

Question 6

why is a catalysts used in chemical reactions?
-refer to activation energy

Answer 6

allows an alternative reaction pathway that has a lower activation energy than the uncatalysed reaction