energy changes (paper 1)

Question 1

exothermic reaction

Answer 1

a reaction that transfers energy to the surroundings

it gives out heat

Question 2

activation energy

Answer 2

the bit of energy needed to get the reaction started
(the minimum amount of energy needed to start a reaction)

Question 3

in an exothermic reaction is the energy of the products lower than the energy of the reactants ?

Answer 3

yes so energy is released to the surroundings

Question 4

examples of exothermic reactions

Answer 4

combustion
hand warmer
neutralisation
oxidation

Question 5

endothermic reactions

Answer 5

a reaction that takes in energy from the surroundings

it takes in heat (gets colder)

Question 6

in an endothermic reaction is the energy of the reactants lower than the energy of the products

Answer 6

yes so the energy is taken into the reaction from the surroundings

Question 7

examples of endothermic reactions

Answer 7

thermal decomposition
photosynthesis
respiration

Question 8

steps for bond energy calculations

Answer 8

1. highlight the bonds broken and bonds made
2. workout the energy for bonds broken
3. workout the energy for bonds made
4. workout the energy change for the reaction

energy change = bonds broken - bonds made

Question 9

temperature change practical method

Answer 9

1. measure 30cm cubed of dilute hydrochloric acid and put it into the polystyrene cup
2. stand the cup inside the beaker as this will make it more stable
3. use the thermometer to measure the starting temp of the acid and record your result
4. measure 5cm cubed of sodium hydroxide solution
5. pour the sodium hydroxide into the cup and fit the lid and gently stir the solution with the thermometer through the hole
6. look carefully at the temp rise on the thermometer
7. when the temperature stops increasing record the highest temp reached in the table
8. repeat these steps and add 5cm cubed of sodium hydroxide to the cup each time

then plot the results on a graph

Question 10

what does the reaction profile of an exothermic reaction look like

Answer 10

the products are at a lower energy than the reactants

the reactants have more energy than the products

the difference between the reactants and the products is the energy released and the difference between the reactants and the hump is the activation energy

Question 11

what does the reaction profile of an endothermic reaction look like

Answer 11

the products are at a higher energy than the reactants

the reactants are at a lower energy than the products