year 8 substances

 WHAT IS AN ELEMENT?

 An ELEMENT is a substance made

up of only one type of atom

 An element can NOT be broken

down

 Examples: oxygen, carbon, gold ATOMS, MOLECULES AND LATTICES

 Atoms in chemical elements can be

arranged in three ways:

1. Single atoms

 E.G. helium, neon

2. Molecules – groups of two or more

non-metal atoms bonded together.

 E.G. oxygen, hydrogen

3. Lattices – 3D arrangement of

particles in a regular pattern

 E.G. carbon, gold

 PROPERTIES OF ELEMENTS

 Each element has a unique set of properties

 Some examples of properties include its: atomic number,

atomic mass, state (at room temperature), colour,

conductivity, density, melting/boiling point

Density

Conductivity

Horizontal rows  periods

Vertical columns  groups

COMPOUNDS

 WHAT IS A COMPOUND?

A COMPOUND is a substance made

up of two or more different atoms

joined (bonded) together

 A compound CAN be broken down

Examples: water, salt, glucose

 Compounds are usually different from the elements they

are made up of

Salt (sodium chloride, NaCl) is a compound made up

of two elements: sodium (a silvery metal) and

chlorine (a green, poisonous gas)!

MINERALS

& ORES

 A naturally occurring

WHAT ARE inorganic solid with definite

MINERALS? chemical composition and an

ordered arrangement

(crystalline structure).

 WHAT ARE MINERALS?

Minerals are pure

substances made up of the

same element or same

compound

Minerals are particular

combinations and

arrangements of atoms

that can be identified by

their physical properties

 Minerals are

naturally occurring:

 Minerals are are not

made by humans

 Most created long ago

during the formation of

earth

Minerals are inorganic:

 Inorganic means they do

not come from living

matter

 Inorganic also means they

do not contain carbons

bonded to hydrogens

Minerals have definite

chemical composition:

 Minerals are

usually compounds

and are made up

of a fixed ratio of

elements

Minerals have an ordered arrangement:

 Minerals are crystal

lattices. This means

they have a regular 3D

arrangement of their

atoms

MINERAL

 Naturally occurring solid substance

 Own chemical composition, crystalline structure

and properties

 Examples: quartz, graphite, calcite

ORE

 Concentrations of minerals in a rock that are

high enough to be extracted for a profit

 Examples: iron ore, gold ore

Appearance of minerals

There are six main physical features of minerals:

1. Colour

2. Hardness

3. Lustre

4. Streak

5. Cleavage

6. Magnetism

 Hardness is how resistant the mineral is to Hardness

scratches

 Mohs Hardness Scale: 1 is the softest

mineral and 10 is the hardest

Lustre

 Lustre is how the mineral interacts with

light to produce a certain appearance.

 There are many different terms that can

be used!

Streak

Colour of a mineral when it is powdered.

Often it is different to the colour of the mineral in its natural state.

 Cleavage

 Cleavage is how a mineral

breaks and what patterns it

makes.

 If we can see a regular shape

when the mineral breaks it

has cleavage.

 If we can see an irregular

shape when the mineral

breaks it has fractures.

 Magnetism

Is the mineral magnetic?

Describing Minerals

COLOUR Light colour, dark colour, colourless, green, purple…

Metallic, earthy, greasy, silky, brilliant, glassy (vitreous),

LUSTRE

pearly, dull, waxy…

STREAK Does it leave a streak? What colour is the streak?

HARDNESS 1-10 on Mohs Hardness Scale

Breaks along cleavage planes to give smooth faces, cleavage

CLEAVAGE

angle is 90 degrees, poor cleavages…

MAGNETISM Magnetic or not magnetic

MIXTURES:

 Many of the substances we use everyday are

not simply elements or compounds but are

mixtures of elements and compounds

Any substance made up of two or more

ingredients is a mixture

WHAT IS A

MIXTURE?

Example: Air is a mixture of oxygen and nitrogen, with water vapour and carbon dioxide.GASEOUS MIXTURE:

Any two gases can be easily mixed because the

particles of a gas are separated by large

distances

Solids can be mixed into gases - Ash particles

from a chimney

Liquids can be mixed into gases - Mist or fog

and clouds (mixture of water droplets)

LIQUID MIXTURES

 MICIBLE: Liquids that can be mixed together - water and food

 IMMISCIBLE: Liquids that do not mix - oil and water

 Gases can be mixed into liquids- Carbon dioxide dissolving in soft drinks

 Solids can be dissolved into liquids to form solutions

 COLLOID: the solid does not dissolve,

but the particles are very small - MILK

 SUSPENSION: if the solid particles are

bigger - Sand in water