C5 Energy Changes

Question 1

Required practical 1 : investigating temperature change (method) (neutralisation)

Answer 1

1: in a polystyrene cup (prevent heat loss)in a beaker, add 30cm 3 of sodium hydroxide (NaOH)
2: measure and record temp on thermometer
3: add 5cm 3 of hydrochloric acid, place the lid on and stir
4: mesure and record temp
5: repeat, adding 5cm 3 every time until 40cm 3 has been added
6: plot graph

Question 2

What are the variables for RP 1, investigating temp changes

Answer 2

INDEPENDENT : volume of sodium hydroxide solution
DEPENDENT : maximum temperature reached
CONTROL: volume of hydrochloric acid , concentration of the hydrochloric acid and sodium hydroxide

Question 3

Examples of endothermic reactions

Answer 3

Melting, boiling, decomposition, metal hydrogen carbonates and acid reactions , photosynthesis

Question 4

Examples of Exothermic reactions

Answer 4

Condensing, freezing, oxidation, combustion, neutralisation, hand warmers, self heating cans

Question 5

Exothermic reaction profile

Answer 5

Reactants above products

Question 6

Endothermic reaction profile

Answer 6

Reactants below products

Question 7

What is bond energy?

Answer 7

The amount of energy required to break a bond (or the amount of energy released when a bond is made)

Question 8

Overall energy change calculation

Answer 8

Energy of nond breaking - energy of bond making

Question 9

If the overall energy change is positive, is the reaction exo or endo?

Answer 9

Endothermic (more energy was used to break the bond that was released)