Topic 1 - Chemistry

Question 1

Focus 1
What is matter?

Answer 1

Matter is anything that has mass and takes up space (volume).
All matter is made up of various types of particles called atoms.
Density can be measured using Mass/Volume or g/mL.

Question 2

Focus 1
What is an atom?

Answer 2

An atom is the most basic unit of matter; the smallest individual unit of a chemical element.
Atoms are represented on the periodic table by their atomic number (no. of electrons or protons), mass number (no. of protons and neutrons), and their element symbol.

Question 3

Focus 1
What are all atoms composed of?

Answer 3

Atoms are made of three different subatomic particles:
Protons
Neutrons
Electrons

Question 4

Focus 2
What is the periodic table?

Answer 4

The Periodic Table is a format which organises all of the elements based on their chemical properties. It is useful for determining and predicting chemical reactions.
Each element is represented by a symbol, for example Hydrogen is represented by “H” and Sodium is represented by “Na”.

Question 5

Focus 2
Describe the organisation of elements in the periodic table using their atomic number.

Answer 5

The elements are organised based on their atomic number, which is their number of protons (+) or electrons (-).
Each row of elements is called a period, and the atomic number increases as you move along the period.
Each column of elements is called a group, and elements that share a group have the same number of electrons in their outer shell.

Question 6

Focus 2
How can the periodic table be used to predict chemical reactions?

Answer 6

Valence electrons determine how reactive an element is: therefore elements in the same group are similarly reactive.
For example, elements in Group 1 are extremely reactive because they only have one valence electron. Elements in Group 8 are non reactive because their electron shells are full (they have no valence electrons) which means they are stable.
The creation of the periodic table was a pivotal point in science due to its ability to categorise elements and predict chemical reactions.

Question 7

Focus 2
Relate the physical and chemical properties of some common elements based in Group 1 of the Periodic Table.

Answer 7

Group 1 - Alkali metals
1 valence electron (+1 cations)
Highly reactive elements; reactivity increases as you move down the group
React very rapidly with water, producing an alkaline solution and hydrogen gas
Shiny and soft enough to cut with a knife
High conductivity

Question 8

Focus 2
Relate the physical and chemical properties of some common elements based in Group 2 of the Periodic Table.

Answer 8

Group 2 - Alkaline earth metals
2 valence electrons (+2 cations)
Reactive elements (not as reactive as alkali metals); reactivity increases as you move down the group
Shiny and soft (not as metallic as alkali metals)
High conductivity

Question 9

Focus 2
Relate the physical and chemical properties of some common elements based in Groups 3 - 12 of the Periodic Table.

Answer 9

Group 3 - 12 - Transition metals
Ductile and malleable
Generally have high densities
Good conductors of heat and electricity
Most have 2 valence electrons; it is assumed that a transition metal has 2 valence electrons unless otherwise specified
Form brightly coloured compounds

Question 10

Focus 2
Relate the physical and chemical properties of some common elements based in Group 17 of the Periodic Table.

Answer 10

Group 17 - Halogens
Exist as diatomic molecules - they have 2 atoms in each molecule
Highly reactive; reactivity increases as you move down the group
Generally react with alkali metals to produce salts

Question 11

Focus 2
Relate the physical and chemical properties of some common elements based in Group 18 of the Periodic Table.

Answer 11

Group 18 - Noble gases
Exist as individual atoms - monatomic molecules
0 valence electrons - almost completely non reactive
Colourless and odourless

Question 12

Focus 3
Describe the tendency of metallic elements to lose their valence shell electrons to form stable positive cations.

Answer 12

Metallic elements (Group 1, 2, & 3) lose their valence electrons to become stable (have full electron shells); stable atoms are very unreactive
Amount of protons (+) is more than the amount of electrons (-); the element is now a positively charged ion (+)
Positively charged ions are called cations

Question 13

Focus 3
Describe the tendency of non-metallic elements to gain valence shell electrons to form stable negative anions.

Answer 13

Non-metals (Group 5, 6, & 7) gain valence electrons to become stable (have full electron shells); stable atoms are very unreactive
Amount of electrons (-) is more than the amount of protons (+); the element is now a negatively charged ion (-)
Negatively charged ions are called ions

Question 14

Focus 3
How are ionic bonds formed?

Answer 14

Ionic bonding is the transfer of electrons between atoms.
Ionic bonding occurs between a metal and non-metal to produce an ionic compound.
Ions bond to form ionic compounds because they are attracted to each other (opposite charges)
Metal cations (+) are attracted to non-metal anions (-)
Ionic compounds are called “salts”.
Transition metals (located between Group 2 & 3) can have multiple valencies. Roman numerals are used to indicate the valency in a compound name.

Question 15

Focus 3
What are polyatomic ions?

Answer 15

Polyatomic ions are created when a number of atoms come together to form a group; the group has a collective positive or negative charge (eg OH-, NO3-, CO32-)

Question 16

Focus 3
Formulas & equations with ionic compounds.

Answer 16

You can’t change the charges of the components; you can only change how many of each one there are
For more complex equations use the “swap and drop” method
List the cation first and the anion second; change the ending of the anion to “ide” (eg sodium chlorine is incorrect - sodium chloride is correct)

Question 17

Focus 3
Systematic naming for ionic compounds.

Answer 17

If the compound name ends in –ide, the anion can be found on the periodic table (non-metal)
If the compound name ends in –ate, it is a polyatomic ion (eg carbonate, nitrate, sulfate, phosphate)
Exception: hydroxide OH- (polyatomic ion) also ends in -ide

Question 18

Focus 4
State the law of conservation of matter.

Answer 18

Matter can’t be created or destroyed
Chemical reactions rearrange atoms to form new substances; no new atoms are created or destroyed.

Question 19

Focus 4
Describe how new compounds are formed.

Answer 19

When two salt solutions are combined, either:
Nothing happens; the ions in the solution remain free and no new compounds are formed
A precipitation reaction occurs; some of the ions join together (bond) to form a new compound that is insoluble (precipitate)

Question 20

Focus 4
Define solubility.

Answer 20

The solubility of a substance is the ability of a substance to dissolve in liquid

Question 21

Focus 4
Define soluble

Answer 21

A substance is soluble if it dissolves in liquid
The liquid is called the solvent and the substance dissolved in the liquid is called the solute which together form a solution

Question 22

Focus 4
Define insoluble.

Answer 22

A substance that does not dissolve in liquid is said to be insoluble

Question 23

Focus 4
Define partially soluble.

Answer 23

Partially soluble compounds dissolve if a small amount of solute is added, but do not dissolve if too much is added.

Question 24

Focus 4
Define precipitate.

Answer 24

A precipitate is the new insoluble compound formed during a precipitation reaction

Question 25

Focus 4 What are soluble ionic compounds?

Answer 25

An ionic compound (salt) can either be soluble or insoluble If a salt is soluble in water (if it dissolves) the metal ions and non-metal ions separate. Metal ions become cations and non-metal ions become anions, and both move freely amongst the water particles. If a salt is insoluble (if it doesn’t dissolve) the metal ions and non-metal ions remain bonded together and don’t become free ions.

Question 26

Focus 4 What happens when two salt solutions are mixed?

Answer 26

If two salt solutions are mixed, two results are generally possible: Nothing happens - the ions in the solution remain free and nothing happens. OR A precipitation reaction occurs - some of the ions join together to form a new compound that is insoluble. The positive metal cation in one salt solution combines with the negative non-metal anion in the other solution and vice versa.

Question 27

Focus 4 Balancing chemical equations in precipitation reactions.

Answer 27

Atoms are not created or destroyed during a chemical reaction; there must be the same amount of atoms on either side of the chemical equation. To balance chemical equations, a coefficient must be added in front of the chemical formulas in an equation (changing the amount of atoms); you can’t change or remove subscripts AB (aq) + XY (aq) → AY + XB. AY and XB are new compounds, and can be either soluble or insoluble. Both compounds may be soluble, both may be insoluble, or only one may be insoluble

Question 28

Focus 5 What is an acid?

Answer 28

Acids are chemical agents that release hydrogen ions when added to water Characteristics include sour taste, react strongly with metals, can burn skin, turn universal indicator yellow - pink

Question 29

Focus 5 What is a base?

Answer 29

Bases (alkalis) are chemical agents that release hydroxide ions when added to water Characteristics include bitter taste, feel slippery, can burn skin, turn universal indicator blue - purple

Question 30

Focus 5 How do you measure the strength of acids or bases?

Answer 30

The strength of an acid or base can be measured using a pH scale The pH scale is a measure of the hydrogen ion concentration The more hydrogen ions a solution has, the more acidic it is The more hydroxide ions a solution has, the more basic it is It spans from 0 - 14 where pH 7 is considered neutral. Neutral substances are neither acidic or alkaline (e.g. pure water)

Question 31

Focus 5 What is a pH indicator?

Answer 31

A pH indicator is a compound that changes colour as the pH of the solution changes (identifying the pH of the solution) Common indicators include universal indicator, litmus, and phenolphthalein.

Question 32

Focus 6 What are neutralisation reactions?

Answer 32

When an acid is added to a base the two solutions react together to neutralise each other if an equal number of hydrogen and hydroxide ions are present. The equation for a neutralisation reaction is Acid + Base → Salt + Water Example: Hydrochloric Acid + Sodium Hydroxide → Sodium Chloride + Water HCl + NaOH → NaCl + H2O Acids can be identified because their formula starts with H. Bases can be identified because their formula starts with OH.