C7 - Energy Changes

Question 1

Exothermic and endothermic reactions in terms of bonds?

Answer 1

Breaking bonds aBsorbs energy,

forRming bonds Releases energy

Question 2

D. Activation energy?

Answer 2

minimum energy required for a reaction to take place

Question 3

What kind of reactions are neutralisation reactions?

Answer 3

exothermic

Question 4

RQ. What equipment do you need to investigate temperature changes?

Answer 4

poly(styrene) cup and thermometer

Question 5

RQ. Method for investigating temperature changes?
safety?
improvements?

Answer 5

• Record initial temperatures of reactants
• mix reactants in cup
• record max/minimum temperatures reached
• Safety = goggles
• improvements= lid for cup, stirring to get even distribution of heat

Question 6

Uses of exothermic reactions? (2)

Answer 6

Chemical hand warmers, self-heating cans

Question 7

3 main endothermic reactions?

Answer 7

Photosynthesis, hydrogen carbonate + acid (sherbet) , dissolving ammonium nitrate in water

Question 8

Equation for reaction in self-heating cans?

Answer 8

calcium oxide + water -> calcium hydroxide

Question 9

Uses of endothermic reactions?

Answer 9

Chemical cold packs

Question 10

How do chemical cold packs work?

Answer 10

They contain ammonium nitrate and water, when ammonium nitrate dissolves, it absorbs energy from surroundings

Question 11

D Bond energy?

Answer 11

Energy needed to break a bond between 2 atoms

Question 12

What units are bond energies measured in?

Answer 12

kJ/mol

Question 13

You can use bond energies to work out…

Answer 13

the energy change for most reactions

Question 14

When new bonds are formed between atoms….

Answer 14

energy is released

Question 15

Energy must be supplied to…

Answer 15

break chemical bonds