Year 8 science revision- CHEMISTRY

Matter

Anything that takes up space, has matter and can be detected by one or more

Density

The amount of mass something has per unit

Mass

The amount of matter in something

Volume

How much space something takes up

Weight

The measured gravitational pull on a mass

Solid particle movement

Particles vibrate and closely packed because it is a fixed structure, and has fixed volume

Liquid particle movement

Particles slide past each other and are connected, have no fixed structure but have fixed volume

Gas particle movement

Move around rapidly, colliding with each other and the sides of the container randomly, and have no fixed structure nor volume

Effect of applying hot thermal energy to a substance

The particles will speed up, as heat will give it energy, and they will spread out, and the substance will enlarge

Effect of adding cold thermal energy to a substance

The particles will slow down, as energy is taken away from them, and they will pack closer together, and the substance will shrink

Density in terms of mass and volume

Density= MASS/VOLUME (mass divided by volume)

Density in terms of the number of particles in a substance’s certain volume

The more closely packed together the particles are, and the more particles there are in a unit, the higher the density

Diffusion

The movement of particles from a higher concentrated area to a lower concentrated area to even out

Element

Simplest chemical forms. Cannot be broken down by non-nuclear reactions

Molecule

Two or more atoms held together by chemical bonds

Compound

Molecules chemically bound together to form a substance

Mixture

Two or more non-chemically bound molecules

Homogeneous mixture

Uniform distribution of molecules

Heterogeneous mixture

Non-uniform distribution of molecules

Atomic number

The number of protons and electrons

Mass number

The number of protons PLUS the number of neutrons

Maximum number of electrons in one shell

2n^2

Number of valence electrons

Ones digit of group number

Number of electron shells

Period number

Physical change

Change in shape, size, state of matter, no new substances formed

Chemical change

Change in colour, smell, temperature, bubbles appearing, irreversible change, new substance formed

Melting

Solid to liquid

Evaporation

Liquid to gas

Condensation

Gas to liquid

Freezing

Liquid to solid

Sublimation

Solid to gas

Deposition

Gas to solid

Reactants

The substances undertaking the chemical reaction

Product

The resulting substance of a chemical reaction

Worded equation

REACTANT+REACTANT——>PRODUCT

Adding heat to a chemical reaction

Speeds up the rate of the reaction due to molecules gaining more energy