Principles of Chemistry - Paper 1

Structure and Movement of Solids

particles are close together, touching, in regular arrangement, vibrate around fixed positions

Structure and Movement of Liquids

particles are touching, irregular arrangement, move randomly

Structure and Movement of Gases

particles are far apart, irregular arrangement, move quickly and randomly

Interconversions between the States of Matter

Melting

Particles gain kinetic energy, move faster, further apart

Boiling

Particles gain kinetic energy, move faster, more particles have enough kinetic energy to overcome intermolecular forces and move further apart.

Condensing

Particles lose kinetic energy, move close together and more slowly.

Freezing

Particles lose kinetic energy, move more slowly and become regularly arranged.

Dilution

process of reducing the concentration of a given solute in its solution, using water

Diffusion

spreading out of particles from a high to low concentration until there is an equal concentration

Solute

substance that dissolves in solvent

Solvent

liquid solute dissolves in

Solution

liquid formed when solute dissolves in solvent

Saturated Solution

solution which contains as much dissolved solid as possible at a particular temperature

Element

substance that only contains one type of atom, cannot be split into anything simpler by chemical means

Compound

two or more elements chemically combined in fixed proportion

Mixture

various substances physiclly combined in any proportion with no chemical reaction

Pure Vs. Impure Substance

Pure: fixed melting and boiling point

Mixture: melt and boil over range of temperatures

Separation Techniques

• filtration

• crystallisation

• simple distillation

• fractional distillation

• chromatography

Filtration

• separate insoluble solid from liquid

Crystallisation

• separate solute from solution

Simple Distillation

• separate components of solution

Fractional Distilation

• separate mixture of liquids

Paper Chromatography

• separate components of mixtures (coloured inks: mixture of dyes)

• same type of paper, same solvent

Rf Value

distance moved by spot/ distance moved by solvent front

Investigation using Paper Chromatography

• put spots of each ink on pencil line

• pour some solvent into bottom of beaker

• place paper in beaker so spots are above level of solvent

• leave until solvent has risen up paper

Atom

smallest piece of element that can still be recognised as that element

Molecule

two or more atoms chemically bonded

Atomic Number

number of protons in atom’s nucleus

Mass Number

total number of protons and neutrons in atom’s nucleus

Isotope

atoms of same element/ same number of protons

dufferent number of neutrons/ different mass number

Relative Atomic Mass

• average mass of atom compared to mass of carbon-12

Electrical Conductivity and Acid-Base Character - Metals

• conduct electricity

• have oxides which are basic, reacting with acids to give a salt and water

Electrical Conductivity and Acid-Base Character - Non-Metals

• do not conduct electricity (except for graphite)

• have oxides which are acidic or neutral

Noble Gases

• do not react

• full outer shell of electrons

Mole

unit for amount of substance

Determining Formula of Metal Oxide by Combustion

• weight 2.4g magnesium ribbon

• heat strongly in crucible untill all forms magnesium oxide

• keep lid on to stop MgO escaping but keep small gap so air can enter

• reweigh crucible + lid + MgO

• reheat and reweigh to constant mass

Determining Formula of Metal Oxide by Reduction

• measure mass of empty boiling tube

• place metal oxide in and measure mass

• pass methane over copper (II) oxide and burn off excess gas

• heat copper (II) oxide strongly using bunsen burner

• heat until metal oxide completely changes colour

• measure mass of tube remaining metal powder

Ionic Bonding in terms of Electrostatic Attraction

strong electrostatic forces of attraction between oppositely charged ions

Why do GIL have high b.p.?

• strong ionic bonds

• between oppsositely charged ions

• require a lot of energy to break bonds

Electrical Conductivity of Ionic Compounds

• solid → strong ionic bonds between many ions in fixed position, ions not free to move

• molten/ dissolved in water → ions are free to move

What is a Covalent Bond?

strong electrostatic forces of attraction between nuclei of atoms that make up bond and shared pairs of electrons

Diamond Properties

• hard

• high m.p.

• does not conduct electricity

Why is diamond hard?

• has tetrahedral lattice structure/ each atom is bonded to 4 other atoms

• not arranged in layers

Why does diamond not conduct electricity

• no delocalised eletrons

• all electrons held firmly in covalent bonds

Properties of Graphite

• soft

• high m.p.

• conducts electricity

Why is graphite soft?

• structure is in layers

• weak forces of attraction between layers

• slide over one another easily

• each atom is bonded to 3 other atoms

Why can graphite conduct electricity?

• one delocalsied electron per carbon atom

• free to move

Why do GCL have high m.p.?

• strong covalent bonds

• many

• require a lot of energy to break bonds