Week 8/9

Question 1

What does the occurrence of temperature change indicate?

Answer 1

That energy has changed form

Question 2

What evidence will chemical change usually produce?

Answer 2

A gas produced
A precipitate is formed
A permanent colour change
An apparent change in mass
A temperature change

Question 3

What may be needed for a reaction to occur or what may be produced as a result of the reaction?

Answer 3

Energy

Question 4

What happens to the bonds when a reactions occurs?

Answer 4

Some bonds are broken and some are formed.

Question 5

If less energy is stored in the products then was present in the reactants, then what happens?

Answer 5

The surplus energy is released as heat.

Question 6

What do all molecules contain? Where is it contained?

Answer 6

Stored chemical energy
Contained within the bonds that are between the atoms that are within the molecules and within the the bonding between the molecules themselves.

Question 7

What is the stored chemical energy called and what is its symbol?

Answer 7

Enthalpy or heat content

H

Question 8

Formula for the change in enthalpy?

Answer 8

△H = H products - H reactants

*△H = change in enthalpy

Question 9

What happens in an endothermic reaction?

Answer 9

△H is +
E products > E reactants
Heat energy added to the reactants (absorbed)

Question 10

What happens in exothermic reactions?

Answer 10

△H is -
E reactants > E products
Heat energy released by reactants

Question 11

What will often happens to the surrounding temperature during an exothermic reaction?

Answer 11

It increases

Question 12

Eg of endothermic reactions?

Answer 12

Photosynthesis, evaporation of water, backing bread

Question 13

Eg of exothermic reactions?

Answer 13

Lighting Bunsen burner, rust, formation of snow in clouds

Question 14

Define redox reaction?

Answer 14

A chemical reaction that involves the transfer of electrons either by gaining or losing them

Question 15

What is involved in oxidation?

Answer 15

Gain of oxygen
Loss of hydrogen
LOSS OF ELECTRONS

Question 16

What is involved in reduction?

Answer 16

Loss of oxygen
Gain of hydrogen
GAIN OF ELECTRONS

Question 17

Acronym for oxidation and reduction?

Answer 17

OIL RIG

Oxidation Is Loss Reduction Is Gain

Question 18

Define the reactivity/activity series?

Answer 18

Ranks metals on their desire to lose electrons
The MORE reactive element wants to form IONS
K wants to lose electrons
Au wants to lose electrons

Question 19

Define soluble?

Answer 19

A substance that is able to be dissolved, especially in water

Question 20

Define insoluble?

Answer 20

A substance that is unable to be dissolved

Question 21

Define precipitate?

Answer 21

When a substance is deposited in solid form from a solution

Question 22

Define ionic compound?

Answer 22

A chemical compound that is held together by electrostatic forces called ionic bonds

Question 23

Define cation?

Answer 23

Positively charged ions

Question 24

Define anion?

Answer 24

Negatively charged ions

Question 25

Describe what happens when a substance dissolves?

Answer 25

The substance will begin to break down into its molecules once in the liquid. It will separate into its ions which are not able to be seen by the naked eye.

Question 26

Define monatomic?

Answer 26

Consisting of one atom

Question 27

Define polyatomic?

Answer 27

Consisting of two or more atoms

Question 28

Define combustion?

Answer 28

Rapid chemical combination of a substance with oxygen, involving the production of heat and light.

Question 29

Define rate of reaction?

Answer 29

The speed at which a chemical reaction proceeds

Question 30

List the five ways that the rate of a chemical reaction can be controlled?

Answer 30

``` Temperature Concentration Agitation Surface area Catalyst ```

Question 31

Effect of temperature on the rate of a chemical reaction?

Answer 31

Increasing the temperature will normally increase the rate of the reaction

Question 32

Effect of concentration on the rate of a chemical reaction?

Answer 32

Increasing the concentration of the reactants will increase the rate of the reaction.

Question 33

Effect of surface area of reactants on the rate of a chemical reaction?

Answer 33

If the reactants is crushed up the rate of reaction will increase

Question 34

Effect of catalysts on the rate of a chemical reaction?

Answer 34

If a catalyst is added then the reaction rate will be sped up

Question 35

Describe what enzymes do?

Answer 35

They hold reactants molecules together until they rearrange to form products. Eg amylase

Question 36

Why are enzymes so important in digestion?

Answer 36

They break down the starches and complex carbohydrates into simple sugars for easy absorption into the body