Chemistry Key Points

Question 1

Atom

Answer 1

The smallest particle of an element that still retains all the properties of that element

Question 2

Element

Answer 2

A substance that cannot be broken down into simpler substances by chemical reactions

Question 3

Compound

Answer 3

Is formed when two or elements combine chemically

Question 4

A molecule

Answer 4

Two or more atoms chemically combined together. It is the smallest particle of an element or compound that can exist on its own

Question 5

Mixtures

Answer 5

When two or more substances are mingled together but not chemically combined

Question 6

Periodic table

Answer 6

An arrangement of elements in order of increasing atomic mass

Question 7

Alkali reactions with air

Answer 7

Forms oxides

Question 8

Properties of alkali metals

Answer 8

Soft, shiny metals that are stored in oil because they react with air and water

Question 9

Alkaline earth metals

Answer 9

Group 2, less reactive

Question 10

Dilute solution

Answer 10

Little solute in a lot of solvent

Question 11

Concentrated solution

Answer 11

A lot of solute in a little solvent

Question 12

Solvent

Answer 12

The liquid in which the solution is made

Question 13

Solute

Answer 13

Substance that dissolves in the solvent

Question 14

Physical change

Answer 14

A change in which no new substance is formed but the original substance gains new properties

Question 15

Chemical change

Answer 15

A change in which at least one new substance is formed

Question 16

Tests for water

Answer 16

Turns anhydrous copper sulfate blue

Cobalt chloride paper from blue to pink

Question 17

Electrolysis

Answer 17

The chemical breakdown of an electrolyte when an electric current is passed through it

Question 18

How is hard water removed by ion exchange

Answer 18

The ions that cause hardness (ca2 ions) are exchanged for ions that do not cause hardness (usually na ions)

Question 19

The atomic number

Answer 19

The number of protons (or electrons) in an atom of an element

Question 20

Mass number

Answer 20

The number of protons and neutrons in an atom of an element

Question 21

Ion

Answer 21

An electrically charged atom or group of atoms

Question 22

How are positive and negative ions formed

Answer 22

Positive ions are formed by the loss of electrons

Negative ions are formed by the gaining of electrons

Question 23

Ionic bond

Answer 23

Formed by the attractive force between a positive and negative ion

Question 24

How are ionic compounds formed

Answer 24

When elements from the left hand side (+) and right hand side (-) of the periodic table combine

Question 25

Ionic bond

Answer 25

Formed when electrons are transferred between atoms

Question 26

Isotopes

Answer 26

Atoms of the same element that have different mass numbers, due to different amounts numbers of neutrons in the nucleus

Question 27

Indicators

Answer 27

Substances that change colour depending on whether they are in an acidic or alkaline solution

Question 28

Fossil feuls

Answer 28

They are hydrocarbons and release energy when they are burned in oxygen
Fuel + O2 = h2 o + CO2 + energy

Question 29

Polymers

Answer 29

Large chain like molecules that are built up from smaller molecules called monomers
Eg polythene is made up from many ethene molecules
Polythene is easily moulded and used in plastic packaging and squeezy bottles

Question 30

Plastics

Answer 30

Plastics are giant molecules