Describing Reactions

Question 1

Chemical Reaction

Answer 1

a change in which atoms are rearranged to create new
substances, usually irreversible.

Question 2

Physical Change

Answer 2

a change that is reversible, in which new substances are not made. E.g. boiling, dissolving.

Question 3

Combustion

Answer 3

Another name for burning. This is when a fuel reacts with oxygen to release energy (Light/heat).

Question 4

Complete combustion

Answer 4

• Lots of oxygen
• Only water and carbon dioxide are produced
• Produces more energy

Question 5

Incomplete combustion

Answer 5

• Little or no oxygen
• Water, carbon monoxide and carbon (soot) are produced

Question 6

Complete Combustion Equation

Answer 6

Methane + Oxygen -> Carbon dioxide + Water
CH4 + O2 -> CO2 + H2O

Question 7

Incomplete Combustion Equation

Answer 7

Methane + (some) Oxygen -> Carbon Monoxide + Water
CH4 + O2 -> CO + H2O

Question 8

Oxidation

Answer 8

When a substance gains oxygen in a reaction.

Question 9

Reduction

Answer 9

When a substance loses oxygen.

Question 10

Can oxidation and reduction happen at the same time?

Answer 10

Yes

Question 11

Things needed to make fire?

Answer 11

Oxygen, heat and fuel.

Question 12

Displacement Reaction

Answer 12

a more reactive element takes the place of a less reactive element in a compound.

Question 13

Thermal Decomposition

Answer 13

A reaction where a substance is broken down using heat.

Question 14

Effervescence

Answer 14

Changing colour and giving off gas.

Question 15

Exothermic

Answer 15

A reaction where energy is released to the surroundings. The change in temperature is always positive.

Question 16

Endothermic

Answer 16

A reaction where energy is taken in by the surroundings. The change in temperature is always negative.

Question 17

What starts the breaking of bonds?

Answer 17

Activation energy

Question 18

Breaking bonds requires…

Answer 18

Energy

Question 19

Making bonds gives out…

Answer 19

Energy

Question 20

Rate of Reaction

Answer 20

Tells you how fast or slow a chemical reaction is happening.

Question 21

The higher the rate of reaction, the ……
the reaction is happening

Answer 21

Faster

Question 22

Reactions don’t happen unless the substances are…

Answer 22

In contact.

The particles of the reactants need to get together so that they can react.

Question 23

Collision Theory

Answer 23

In order for a reaction to occur, particles must collide and colliding particles must have enough energy to break existing bonds.

Question 24

Activation Energy

Answer 24

The minimum amount of energy needed to start a reaction.

Question 25

How to increase reaction rate?

Answer 25

• Make collisions happen more often (increasing concentration,
  surface area, temperature).
• Increase the proportion of collisions that have enough energy (adding a catalyst or increasing temperature).