Chemistry Key Words Year 9

Atom

Smallest particle of an element

Boiling point

The temperature at which a liquid changes to a gas

Carbon dioxide test

Bubble gas through limewater, limewater turns cloudy if carbon dioxide is present.

Chemical reaction

A process where new substances are formed

Chemical symbol

A one or two letter code that represents an element ( e.g. O for oxygen). First letter must be capital, second letter is lower case e.g. He

Chemical formula

Shows the type and number of atoms joined together in a molecule e.g. H2O

Chlorine test

Hold damp litmus paper in the gas. It turns white (bleached) if chlorine is present.

Chromatography

A method to separate mixtures and help identify substances.

Compound

A substance made up of two or more elements chemically combined

Distillation

A method of seperating mixtures using differences in boiling points

Element

A substance made of only one type of atom

Filtration

A process to separate an insoluble solid from a liquid.

Formulation

A mixture designed as a useful product with carefully measured amounts of each substance

Group

A column on the periodic table

Hydrogen test

Hold a lit splint in the gas. It causes a squeaky pop sound if hydrogen is present

Impure substances

contain two or more elements or compounds not chemically combined

Melting point

The temperature at which a solid becomes a liquid

mixture

Two or more substances not chemically combined

Mobile phase

The solvent in chromatography

Molecule

Two or more atoms chemically bonded

Oxygen test

Hold a glowing splint in the gas. It relights if oxygen is present.

Periodic table

A chart that shows all known elements

Physical process

A change that doesn't form a new substance, e.g. melting

Pure substance

A single element or compound, not mixed with anything else.

Rf value

A way of identifying a substance after chromatography. Calculated using the formula:

Rf = distance moved by substance/ distance moved by solvent

Separation technique

A method used to separate mixtures into individual substances e.g. distillation, chromatography, filtration.

Solute

solid that dissolves in a solvent

Solution

A solute dissolved in a solvent

Solvent

A substance that dissolves a solute to from a solution.

Stationary phase

The part in chromatography that does not move.

Symbol equation

A way of describing a chemical reaction using chemical symbols and formulae

Word equation

A way of describing a chemical reaction using the names of the substances.

Crystallisation

Used to separate solids from solution

calculation for Rf value

Distance moved by substance/ Distance moved by solvent

what is a hydrocarbon

a compound with only hydrogen and carbon

Name and alkane with only 3 carbon atoms

Propane

What is the general formula for an alkane

CnH2n+2

What does combustion mean

Something reacting with oxygen

What process is used to separate crude oil into similar chain lengths

fractional distillation

what property of the chains is used to separate crude oil into similar chain lengths

boiling point

Name 3 fractions of crude oil

petrol, diesel , bitchemen

what is the trend in the boiling points of alkanes as the molecules get longer

they increase

what is the name of C4H10

butane

Are alkanes saturated or unsaturated

saturated

what is the definition of a formulation

a mixture designed for a specific thing

what is the definition of a compound

2 or more elements chemically bonded together

Fuels usually react with oxygen to produce carbon dioxide, but sometimes a different oxide of carbon is made

Name this different oxide of carbon and explain why it is produced

carbon monoxide is produced because the combustion was incomplete because there was not enough oxygen

What is the process of breaking down long hydrocarbons into smaller ones

cracking

Balance the equation for one possible reaction of dodecane

C12H26 → C6H14 + C2H4

C12H26→ C6H14 + 3CH4

Suggest why changing dodecane into smaller molecules is useful

Because we use smaller molecules so they are in demand. Smaller molecules are more useful. Smaller molecules are more flamable.

Balance this equation:

MgO + HBr → MgBr₂ + H₂O

Mg + 2HBr → MgBr₂+H₂O

Boiling point for short chains

Low

Boiling point for long chains

High

Flammability for short chains

High

Flammability for long chains

Low

Viscosity for short chains

Low

Viscosity for long chains

High

2 types of cracking

Catalytic and Steam cracking

what do you need for catalytic cracking

high temperature, catalyst

what do you need for steam cracking

Very high temperature and steam

Are alkenes saturated or unsaturated

unsaturated

General formula for alkene

C_nH_2n