Exothermic reactions release energy to the surroundings
Endothermic reactions absorb energy fromsurroundings
Exothetmic reactions include combustion, oxidation and neutralisation
Endothermic reactions include thermal decomposition
An example of exothermic would be self heating cans and hand warmers
An example of endothermic is sports injury packs
Exothermic reactions causes surroundings to increase in temp
Endothermic reactions cause surroundings to decrease in temp
Bond breaking absorbsenergy
Bond making releases energy
BB < BM is exothermic
BB > BM is endothermic
Chemical reactions can only occur when reacting particles collide with each other
Delta h is the difference in energy levels between the products and reactants
Negative delta h is exothermic
Positive delta h is endothermic
Simple cells can be made by connecting 2 different metals in contact with an electrolyte
Hydrogen fuel cells at negative electrode
2H2 + 4OH- -> 4H2O + 4e-
Hydrogen fuel cells at positive electrode
O2 + 2H2O + 4e- -> 4OH-
Hydrogen fuel cell overall equation
2H2 + O2 -> 2H2O
The voltage produced by a cell is dependent upon the type of electron and electrolyte
Type of electron
Different metals will react differently with the same electrolyte
electrolyte used
Different ions in solution with react differently with the metal electrodes used
How many cells you use
A battery is formed by connecting two or more cells together in series . The voltage of the individual cells combine together so there is a bigger overall voltage
RP - temperature change
1)put 30 cm3 of hydrochloric acid in a polystyrene cup
2)stand the cup in a beaker
3) measure the temp of the acid
4)measure 5cm3 of sodium hydroxide and pour into the cup
5)put the lid on and stir the solution with the thermometer
6) record the temp then the temp stops changing
7)repeat steps 4-6 until a total of 40 cm 3 of sodium hydroxide has been added
