Topic 12 : Energetics Flashcards
1
Q
exothermic reactions
A
- transfers heat energy to surroundings
- increase in temp of surroundings
- energy of the reactants is higher than energy of products
2
Q
endothermic reactions
A
- takes in heat energy from surroundings
- decrease in temp of surroundings
- energy of the reactants is lower
than energy of products
3
Q
ΔH : enthalpy change
A
energy of products - energy of reactants
4
Q
activation energy
A
minimum energy needed to start a reaction
5
Q
breaking bonds ( BENDO )
A
- energy must be supplied to break existing bonds
- this takes heat energy in from surroundings and leads to decrease in temp
- ENDOTHERMIC
6
Q
making bonds ( MEXO )
A
- when new bonds are made energy is released
- this release heat energy to surroundings and leads to increase in temp
- EXOTHERMIC
7
Q
endothermic reaction in terms of bonds
A
- energy required to break bonds is greater than the energy released when new bonds are made
8
Q
exothermic reaction in terms of bonds
A
energy released when new bonds are made greater than the energy required to break bonds
9
Q
energy change
A
energy of ( bond breaking - bond making )
10
Q
when do energy changes take place
A
- salts dissolve in water
- neutralisation reactions
- precipitation reactions
- displacement resctions
11
Q
how to measure a temperature change
A
- put polystyrene cup in a beaker of cotton wool
- this insulates the mixture and reduces heat loss
- add known volume of first reagent to cup and measure initial temp
- add measured volume of 2nd reagent and stir it
- measure max/min temp and calculate temp increase/decrease
12
Q
A
