C5 energy changes

Question 1

Exothermic reaction

Answer 1

Give out energy
Temp of surrounding goes up
Combustion, oxidation, neutralisation 
Self heating cans, hand warmers
Less energy needed to break bonds than make new binds exo overall

Question 2

Endothermic reaction

Answer 2

Takes in energy
Temp of surroundings drops
Thermal decomposition, reaction of critic acid and sodium hydrogencarbonate, photosynthesis
Sports injury packs
More energy needed to break bonds than released on making new bonds endo overall

Question 3

Required practical- investigate the variables that affect temperature changes in reacting solutions such as, acid + carbonates, neutralisations, displacement of metals

Answer 3

I- Concentration of acid (mol/dm3)

D- temp (degrees Celsius)

Question 4

Colliding particles

Answer 4

Collision and no reaction= unsuccessful
Collision and reaction= successful
Have enough energy to react

Question 5

Activation energy

Answer 5

Energy needed to start reaction

Question 6

reaction profile

Answer 6

The relative energies of reactant and product
Activation energy
Overall energy change of a reaction

Question 7

Breaking and making bonds

Answer 7

1. Energy needed to break the bonds in the reactants into separate atoms ( activation energy -endothermic)
2. Separated atoms combine to form the products, energy is releases (exothermic)

Question 8

Bond breaking

Answer 8

Endothermic

Question 9

Bond making

Answer 9

Exothermic

Question 10

Batteries

Answer 10

2 or more cells connected together in series to provide a greater voltage

Question 11

Voltage produced depends on

Answer 11

Type of electrode and electrolyte

Relative reactivities of 2 metals

Question 12

Non rechargeable

Answer 12

Stop when 1 reactant used up
Have to be recycled due to heavy metals= contamination
Alkaline battery

Question 13

Rechargeable batteries

Answer 13

Expensive
Used many times
Recharged as chemical reaction reverses when external electrical current is supplied

Question 14

Fuel cell

Answer 14

Special type of electrical cell
Don’t need recharging/replacing
Have fuel tanks which need refilling with hydrogen
Reacts with oxygen from air
Pollution free
Exothermic reaction produces electrical energy= efficient

Question 15

Advantages of fuel cells

Answer 15

Direct energy transfer 
Fewer transfer stages
Less polluting 
Last longer
Uses oxidation 
Exothermic 
Redox reaction