AQA Combined Science - Chemistry

atom

the smallest part of a chemical element that can still be recognised as an element

element

contains only one type of atom

compound

two or more different types of elements chemically bonded together

mixture

two or more elements or compounds not chemically bonded together

filtration

separate an insoluble solid from a liquid

evaporation

isolate a soluble solid from a solution

distillation

isolate a pure liquid from a mixture

fractional distillation

separate mixtures with similar boiling points

paper chromatography

separate dyes in ink

protons

mass 1, charge +1

neutrons

mass 1, no charge

electrons

mass negligible, charge -1

JJ Thompson

discovered the electron

Ernest Rutherford

discovered that atoms contain a tiny 'massive' nucleus

Neils Bohr

discovered that electrons orbited the nucleus in certain fixed energy levels called shells

ion

a charged particle caused by the loss/ gain of electrons

isotope

atoms that have same number of protons but different numbers of neutrons.

outer shell

contains the same number of electrons as the group number

group 8

unreactive because they have a full outer shell

Mendeleev's periodic table

ordered by atomic weight with gaps for undiscovered elements

modern periodic table

ordered by atomic number and grouped by property

group 1

also called alkai metals

group 1 ions

has a 1+ charge

group 1 trends

reactivity increases down the group, melting point decreases down the group

group 7

also called halogens

halide ion

has a 1- charge

group 7 trends

reactivity decreases down the group, melting point increases down the group

group 1 reactivity

The outer shell electron is further away from the nucleus, so the electrostatic attraction is weaker. This makes it easier to remove.

group 7 reactivity

The outer shell is further away from the nucleus, so the electrostatic attraction is weaker. This makes it harder to gain an electron

properties of solids

have a fixed shape and cannot be compressed

properties of liquids

have a fixed volume but can flow and change their shape

properties of gasses

have no fixed shape or volume and can be compressed easily

solid particles

vibrate in fixed positions

liquid particles

slide past each other but are still touching

gas particles

move very quickly in all directions

heating particles

causes particles to vibrate more

phase changes

during phase changes the temperature remains constant

covalent bonding

The attraction between two atoms that share one or more pairs of electrons

ionic bonding

The electrostatic force of attraction between a positively charged ion and a negatively charged ion

metallic bonding

positive nuclei surrounded by a sea of delocalised electrons

non-metal ions

have negative charges

metal ions

have positive charges

metal and non-metal

ionic bonding

metals

metallic bonding

non-metals

covalent bonding

outer shell

requires 8 electrons to be energetically stable

properties of ionic lattices

high melting points and conduct electricity when dissolved or molten

properties of giant covalent compounds

high melting points, insoluble in water, do not conduct electricity

properties of metals

high melting points, conducts electricity, shiny

high melting point

a lot of energy is required to break several strong bonds

low melting point

not much energy require to break weak van der waals forces

conductivity

a charged particle is free to move and transport a current

graphene

a single sheet of inter-locking hexagonal carbon atoms

fullerene

A large cage like structure made up of hexagonal rings of carbon atoms

prefix nano

1 x 10^-9

alloy

a mixture of two or more elements one of which is a metal

Mr / RFM

mass of 1 mole of a compound

mole

6.02x10^23 molecules

moles (mol) =

mass (g) / Mr (g/mol)

mass (g)

Moles (mol) x Mr (g/mol)

chemical coefficients

give the ratio of reactants and products in a chemical reaction

Ar

atomic mass of an element found on the periodic table

calculating Mr

add together the Ar of all the atoms in the chemical formula

limiting reagent

the reagent that gets used up first in a reaction

conc (g/dm^3) =

amount of solute (g) / volume of solution (dm^3)

conc (mol/dm^3) =

amount of solvent (mol) / volume of solution (dm^3)

cm^3 to dm^3

divide by 1000

dm^3 to cm^3

multiply by 1000

titration

method used to measure accurately the volumes of solution that react together

ore

a rock that contains enough metal to make it economically worthwhile to extract

reactivity series

a list of elements in order of their reactivity

displacement

where a more reactive element takes the place of a less reactive element in a compound

use of displacement

to extract a pure metal from a compound

OIL RIG

oxidation is loss, reduction is gain

oxidation

when a substance reacts to lose electrons

reduction

when a substance reacts to gain electrons

metal extraction

hydrogen and carbon are used to extract metals by displacement

electrolysis

the method used to extract metals more reactive than carbon

acid

a substance that dissociates to form H+ ions

acid + metal

a salt and hydrogen

acid + base

a salt and water

acid + alkali

a salt and water

acid + metal carbonate

a salt, water and carbon dioxide.

sulphuric acid

produces sulphates

hydrochloric acid

produces chlorides

nitric acid

produces nitrates

base

a substance that can neutralise an acid

alkali

a base that is soluble in water

acidic pH

<7

basic pH

>7

strong acid

fully dissociates in water

concentrated acid

a high concentration of H+ ions

pure wate pH

7

pH

a measure of H+ concentration

[H+]=

1 x 10^-pH

cathode

negative electrode

anode

positive electrode

anion

negatively charged ion

cation

positively charged ion

anion movement

move towards the anode