Y11 Mock Energy Changes

Question 1

exothermic reaction definition

Answer 1

a reaction that transfers energy to the surroundings so the temperature of the surroundings increase

Question 2

endothermic reaction definition

Answer 2

reaction that has taken in energy from surroundings so the temperature of the surroundings decrease

Question 3

steps for bond energy calculations

Answer 3

highlight bonds broken(left) and bonds made (right)
work out energy for bonds broken (no of bonds x bond dissociation energy)
work out energy for bonds made
work out enthalpy change for reaction (bonds broken - bonds made)

Question 4

how to tell a reaction is exothermic or endothermic from energy change value in bond calculation

Answer 4

exothermic if the answer is negative
endothermic if the answer is positive

Question 5

what is shown on an exothermic energy change graph

Answer 5

energy of the products is lower than the energy of the reactants meaning energy is transferred to the surroundings

Question 6

energy in terms of bonds in an exothermic reaction

Answer 6

energy released when new bonds are formed is greater than the energy taken in breaking the existing bonds

Question 7

what does an endothermic energy change graph show

Answer 7

energy of the reactants is lower than energy of the products meaning energy is taken in

Question 8

energy in endothermic reaction in terms of bonds

Answer 8

energy needed to break existing bonds is greater than the energy released when new bonds are formed