S1.1: The Particle Nature Of Matter

Polyatomic ions

ions that are made of more than one atom

State symbols

solid (s), liquid (l), gas (g), and aqueous (aq)

Mole

the SI base unit used to measure the amount of a substance

Mixture

A combination of two or more substances that are not chemically combined in a fixed ratio and thus can be separated via physical methods and also retains individual identities of the element/compounds that makes it

Pure substance

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

Elements

A molecule composed of one kind of atom; cannot be broken into simpler units by chemical reactions.

Compounds

two or more elements chemically combined in fixed ratios

Heterogeneous mixture

A mixture that is not uniform in composition; components are not evenly distributed throughout the mixture with visible phase barrier

Homogeneous mixture

A mixture in which substances are evenly distributed throughout the mixture with uniform composition

Atoms

Smallest unit of matter, with a nucleus consisting of protons and neutrons and electrons orbiting the nucleus

Molecules

Groups of two or more atoms held together by chemical bonds

Ions

Atom or molecule with a net electric charge due to loss or gain of one or more electron

Avogardo's constant

6.02 x 10^23 particles

Significant Figure Rules

1. non-zeros are always significant; 2. zeros between two other sig figs are significant; 3. all final zeros after the decimal point are significant; 4. zeros used solely for spacing the decimal point are not significant unless a decimal point is present

Filtration

Removes an insoluble solid from a liquid/ solution

1. Mixture is poured through a filter paper held in a funnel.

2. Residue remains in the filter paper and does not pass through

3. Filtrate is able to pass through the pores of the paper and collected in the beaker

Solvation

Separates a heterogenous mixture of two solids based on differences in solubility.

1. one of the substances is soluble in a solvent, but the other solid is insoluble.

2. the solvent molecules (often water) surround the soluble molecules and dissolve the solid into a solution.

3. insoluble solid separated by filtration.

4. soluble substance separated from the solution by evaporation.

Evaporation

Separates a mixture which has a solute dissolved in a solvent

1. Heat solution in evaporation dish

2. Solvent evaporates leaving the solute behind

Distillation

Separates liquids based on their volatility

1. Place water ethanol mixture in round

   bottom flask

2. Heat mixture ethanol evaporates first (lower boiling point)

3. ethanol rises up the distillation column and

   passes through the condenser

4. ethanol cools and condense back to a liquid

   to be collected in a flask

Chromatography

Separates a mixture of solutes in a solvent

1. Dissolve solute mixture in a solvent (mobile phase)

2. Place drops of solution on chromatography paper (stationary phase)

3. Place chromatography paper so that bottom is suspended in solvent

4. Solvent moves up through stationary phase

5. Different solutes move through the stationary phase at different rates depending

   on their solubility and affinity for the stationary phase

Recrystallisation

Removes impurities that are mixed in with a solid

1. impure mixture dissolved in a hot solvent to

   make a saturated solution

2. solution is cooled causing the solubility of the dissolved solids to decrease

3. The desired product forms crystals leaving

4. The impurities in the solution which is then filtered to obtain the pure product.

Kinetic Molecular Theory

• Matter is made up of small particles

• All particles have kinetic energy

• Kinetic energy is proportional to the temperature of the substance

• Collisions between particles are elastic ∴ no loss in kinetic energy

Equation for density

Density = Mass / Volume

where:

• Density is measured in units (kg/m³) or (g/cm³)

• Mass is the amount of matter in an object, measured in units (kg) or (g)

• Volume is the amount of space occupied by an object, measured in units (m³) or (cm³)

States of matter

solid, liquid, gas, plasma

Liquid vs aqueous

liquid is the melted physical state of a substance (as apposed to solid or gas)

aqueous means dissolved in water

Features of a solid

• cannot be compressed

• particles are very close together

• strong forces of attraction

• fixed shape

• fixed volume.

• cannot flow

Features of a liquid

• cannot be compressed.

• particles are quite close together

• weaker forces of attraction

• not fixed shape (shape of bottom of container)

• fixed volume

• can flow

• particles move more freely

Features of a gas

• can be compressed

• particles are far apart

• Weakest forces of attraction

• not a fixed shape

• not a fixed volume (same shape as the container)

• volume depends on the temperature and the pressure

Changes in states of matter

Condensation, Evaporation, Sublimation, Melting, Freezing

Evaporation vs boiling

Evaporation occurs at the surface of the liquid and can occur at any temperatures, turning liquid into gas. Boiling occurs at a specific temperature, a change of state form liquid to gas throughout the liquid (so bubbles formed within the liquid)

Exothermic reaction

a chemical reaction in which heat is released to the surroundings

Endothermic reaction

A reaction that absorbs energy

Endothermic vs. Exothermic

Endo: Heat absorbed H>0

Exo: Heat released H

Temperature

A measure of the average kinetic energy of motion of the particles of a substance.

Celsius scale

Based on the freezing and boiling points of water

Kelvin (K) scale

The temperature scale that assigns 0 K to the coldest temperature possible, absolute zero (-273 C), the temperature at which molecular motion stops. The size of the kelvin is identical to that of the Celsius degree.
Directly proportional to the average kinetic energy of the particles in the substance.

Celcius to Kelvin

K=C+273

Directly proportional relationship

as one amount increases, another amount increases at the same rate. (when x doubles, y doubles)

Inversely proportional relationship

a change in one quantity causes a change by the same factor, in the opposite direction, of another quantity. (when x doubles, y halves)

Heating and cooling curves

Sloped line: Heat is transformed into kinetic and potential energy. Average kinetic energy increases as temperature increases

Horizontal line: Energy input used to overcome intermolecular forces and change the state. Heat is therefore only transformed into potential energy. Average kinetic energy of the particles does not change and therefore the temperature remains constant

Assumptions of Ideal Gases

1. no interaction between gas molecules

2. collisions of gaseous molecules are perfectly elastic

3. gas particles move in continuous, rapid, random motion

4. no forces of attraction between gas particles

5. temperature of gases depend on average kinetic energy

pressure

the amount of force exerted per unit area of a surface

Volume

The amount of space an object takes up

kilopascals to pascals

x1000

Convert between the units of meters cubed, (m3) decimeters cubed (dm3), and centimeters cubed (dm3)

1 cubic metre (m^3)= 1000 cubic decimetre (dm3)

1 cubic metre(m^3)= 1,000,000 cubic centimetre (dm3)

Mole formula

moles = mass/molar mass

empirical formula

a formula with the lowest whole-number ratio of elements in a compound