C7

Question 1

Activation energy

Answer 1

The minimum energy needed for a reaction to take place

Question 2

Bond energy

Answer 2

The energy required to break a specific chemical bond

Question 3

Endothermic reaction

Answer 3

A reaction that takes energy from the surroundings

Question 4

Exothermic reaction

Answer 4

A reaction that transfers energy to the surroundings

Question 5

Reaction profile

Answer 5

Diagrams that show the relative energies of the reactants and products in a reaction

Question 6

Aim of investigating temperature changes required practical

Answer 6

To investigate the variables that affect temperature changes in reacting solutions

Question 7

Equipment for required practical (investigating temperature changes)

Answer 7

Polystyrene cup, thermometer, 250 cm3 glass beaker, measuring cylinder, top pan balance

Question 8

Method for reacting 2 solutions (acid and alkali)

Answer 8

Place polystryrene cuo inside glass beaker, measure 25cm3 of each liquid, place one of liquids in polystyrene cup, record temp of solution, add second solution and record highest or lowest temperature, change independant variable and repeat experiment

Question 9

Possible harms of RP

Answer 9

may irritate skin or eyes so could wear gloves or goggles

Question 10

What does a reaction profile show

Answer 10

The relative energy of the reactants and products and the energy changes during a reaction.

Question 11

What reaction is it when the reactants have more energy than the products

Answer 11

Exothermic

Question 12

What reaction is it when the reactants have less energy than the products

Answer 12

Endothermic

Question 13

What percentage of reactions are exothermic and endothermic

Answer 13

90% exothermic and 10% endothermic

Question 14

Examples of exothermic reactions

Answer 14

Combustion reactions, most neutralisation

Question 15

Uses of exothermic reactions

Answer 15

Self heating cans and hand warmers

Question 16

Examples of endothermic reactions

Answer 16

Thermal decomposition, the reaction of citric acid and sodium hydrocarbonate

Question 17

Use of endothermic reaction

Answer 17

Instant ice packs to treat a sports injury

Question 18

In a reaction profile for an exothermic reaction, what does the diagram show

Answer 18

The reactants of the chemical equation having more energy than the products (line goes down)

Question 19

In a reaction profile for an endothermic reaction, what does the diagram show

Answer 19

The products to have more energy than the reactants
Diagram goes up to down

Question 20

How do exothermic reacts link to animals?

Answer 20

All warm-blooded animals rely on exothermic reactions in respiration to keep their body temp steady

Question 21

Example of thermal decomposition:

Answer 21

-Decomposition of calcium carbonate.
-When heated, it forms calcium oxide and carbon dioxide
-the calcium carbonate needs to absorb energy from the surroundings to be broken down

Question 22

When can you feel an endothermic reaction?

Answer 22

When you eat a sherbet sweet you can feel the sherbet dissolving in the water in your mouth takes in energy

Question 23

Bond breaking

Answer 23

Energy has to be supplied to break chemical bonds (endothermic)

Question 24

Bond making

Answer 24

Energynis transferred to the surroundings (exothermic)