C5

Question 1

When is energy conserved?

Question 2

what is an exothermic reaction? eg?
what are the every day uses?

Answer 2

-Exothermic transfer energy to the surroundings usually by heating.This is shown by a rise in temperature
-Eg is combustion burning fuels gives out a lot of energy
-Eg neutralisation reactions
acid+ alkali
-Eg oxidation reactions
-Everyday uses for exothermic are self-heating cans and hand-warmers

Question 3

what is endothermic reactions? eg?
what are everyday uses?

Answer 3

-Endothermic reactions take in energy from the surroundings.This is shown by a fall in temperature
-Eg-Thermal decomposition and reaction between citric acid and sodium hydrogencarbonate
-Everyday uses- sports injury packs

Question 4

PRACTICAL
ENERGY TRANSFER CAN BE MEASURED

4 steps for acid concentration on the energy released in neutralisaiton

Answer 4

1) Measure the amount of energy released by a chemical reaction by taking the temperature of the reagents mixing them in a polystyrene cup and measuring the temperature of the solution at the end of the reaction
2) Biggest problem with energy measurements is the amount of energy lost to the surroundings
3) You can reduce it a bit by putting the polystyrene into a beaker of cotton wool to give more insulation and putting a lid on the cup to reduce energy lost by evaporation
4)This method works for neutralisation reactions or reactions between metals and acids or carbonates and acids
5)You can also use this method to investigate effect different variables have on the amount of energy transferred EG mass or concentration of reactants used

Question 5

what does the exothermic reaction profile show?

what is activation energy?

what does the endothermic reaction profile show?

Answer 5

EXOTHERMIC
-The products are at lower energy then reactants.

-activation- intial rise in energy represents the energy needed to start the reaction
-Its the minimum amount of energy reactants need to collide with each other and react.
-Greater the activation the more energy needed to start the reaction-this has to be supplied

ENDOTHERMIC
-Products are higher at energy than reactants
-difference in height represents overall change during the reaction