Module 3

Question 1

Identify signs of a chemical change

Answer 1

Signs of Chemical Change:
- Evolution of a gas
- Formation of a precipitate
- Colour change
- Significant temperature change
- Production of an odour
- Dissolution of a solid

Question 2

Define synthesis

Answer 2

Synthesis is when at least 2 substances combine to form a new substance

Question 3

Define decomposition

Answer 3

Decomposition is when a reactant is broken down into at least 2 products

Question 4

Identify forms of decomposition

Answer 4

Forms of Decomposition:
- Thermal decomposition – heat energy
- Electrolysis – electrical energy
- Decomposition by light energy

Question 5

Define combustion

Answer 5

Combustion is the process of burning a fuel - usually a hydrocarbon - in the presence of oxygen, releasing thermal energy

Question 6

Identify the chemical equation of combustion

Answer 6

Chemical Equation of Combustion: Hydrocarbon + Oxygen Gas → Carbon Dioxide + Water

Question 7

Define complete combustion

Answer 7

Complete Combustion occurs when oxygen is plentiful and produces carbon dioxide

Question 8

Define incomplete combustion

Answer 8

Incomplete Combustion occurs when oxygen is limited and produces carbon monoxide

Question 9

True or False. When the amount of oxygen is less than 50% of the required amount for the reaction to combust completely, methane can be produced from larger hydrocarbons

Answer 9

True

Question 10

Define precipitation reaction

Answer 10

Precipitation Reaction is the process of mixing 2 transparent ionic solutions to form a precipitate

Question 11

Define spectator ions

Answer 11

Spectator Ions are ions that are not involved in the formation of a precipitate – eliminated in net ionic equations – aqueous for reactants and products

Question 12

Neutral Species Equation →…

Answer 12

Neutral Species Equation → Complete Ionic Equation → Net Ionic Equation

Question 13

Define the SNAAP Rule

Answer 13

SNAAP Rule – All of the initials are soluble; never form a precipitate
- Sodium
- Nitrate
- Ammonium
- Acetate
- Potassium

Question 14

Define neutralisation equation

Answer 14

Neutralisation Reaction is a reaction between an acid and base of equal magnitude on the pH scale

Question 15

Identify the chemical equation for neutralisation

Answer 15

Acid + Base → Salt + Water

Question 16

Identify the chemical equations for acid + metal carbonate

Answer 16

Acid + Metal Carbonate → Salt + Water + Carbon Dioxide

Acid + Metal Hydrogen Carbonate → Salt + Water + Carbon Dioxide

Question 17

Identify the chemical name for limewater

Answer 17

Calcium Hydroxide

Question 18

Define limewater test

Answer 18

Limewater Test detects the presence of carbon dioxide gas

Question 19

Define pop test

Answer 19

Pop Test detects the presence of hydrogen gas

Question 20

Identify a toxic food source for the Indigenous population

Answer 20

The fruit of the cycad

Question 21

Outline the process of how the Indigenous population removed the toxins from the cycad

Answer 21

The poison within the fruit was removed through:
- Leaching: The kernels are cut open, grounded, and soaked in water – the toxins are soluble in water
- Fermentation: The kernels are stored in a moist environment for months till fermentation
- Straining: The kernels are put in dilly bags and placed over running water to strain the toxins
- Heated and Dried: Increases solubility of toxins and denatures toxic proteins

Question 22

Identify the chemical reaction for metal + water

Answer 22

Metal + Water → Metal oxide + Hydrogen Gas

Question 23

Identify the chemical reaction for metal + aqueous acid

Answer 23

Metal + (Dilute) Acid → Salt + Hydrogen Gas

Question 24

Outline when metal and metal ions react

Answer 24

Metal only reacts with metal ions if the metal is more reactive, displacing the ions

Question 25

Define activity series of metals

Answer 25

Activity Series of Metals is a ranking of reactivity of metals in a descending order

Question 26

The reactivity of metals can be explained by which periodic trends?

Answer 26

Interdependence of Reactivity of Metals and Trends within the Periodic Table: - Atomic Radius - Ionisation energy - Electronegativity

Question 27

Define redox reaction

Answer 27

Redox Reaction is a reaction where oxidation and reduction occurs simultaneously in each individual half equation – involves the transfer of electrons

Question 28

Define oxidising agent

Answer 28

Oxidising Agent is a chemical that oxidises other chemicals; itself is reduced

Question 29

Define reducing agent

Answer 29

Reducing Agent is a chemical that reduces other chemicals; itself is oxidised

Question 30

Identify the rules of oxidation number

Answer 30

Rules of Oxidation Number: - The oxidation number of an element is zero - The oxidation number of a simple ion is the charge - Hydrogen has an oxidation number of +1 when it forms compounds with non-metals except in metal hydrides – the oxidation number of hydrogen is −1 - Oxygen usually has an oxidation number of −2 except in compounds with fluorine, where oxygen has a positive oxidation number. In peroxides, oxygen has an oxidation number of −1 - The sum of the oxidation numbers in a neutral compound is zero

Question 31

Define galvanic cell

Answer 31

Galvanic Cell is a type of electrochemical cell in which chemical energy is converted into electrical energy

Question 32

Define anode

Answer 32

Anode is the electrode where oxidation occurs at the anode; electrons leave the electrode

Question 33

Define cathode

Answer 33

Cathode is the electrode where reduction occurs at the cathode; electrons enter the electrode

Question 34

Identify the purpose of the salt bridge

Answer 34

The salt bridge – internal circuit – maintains electrical neutrality by: - Cations from the salt bridge move towards the cathode - Anions from the salt bridge move towards the anode

Question 35

Calculate the voltage produced by a galvanic cell

Answer 35

The voltage (E0) = E0 of the cathode - E0 of the anode

Question 36

State the collision theory

Answer 36

Collision Theory states for a reaction to occur, the reactant particles must: - Make contact (collide) with each other - Collide with sufficient energy to break bonds within the reactants - Collide with the correct orientation to break the bonds within the reactants to allow the formation of new products

Question 37

Define activation energy

Answer 37

Activation Energy is the minimum energy that a collision must possess for a reaction to occur

Question 38

Calculate the rate of reaction

Answer 38

Rate of Reaction = ΔConcentration / Time

Question 39

Outline the factors for the rate of reaction

Answer 39

The rate of reaction is affected by: - Temperature – increases the proportion of molecules that have energy exceeding the activation energy - Surface Area – increases the exposed area for collisions - Concentration – increases the amount of molecules - Use of a catalyst – reduces the activation energy

Question 40

Define enthalpy

Answer 40

Enthalpy (ΔH) is the total energy possessed by a substance