Matter and materials

Properties of matterStrengthThermal and electrical conductivityMagnetic propertiesSolubilityMalleability and ductilityDensityMP and BPAtom that bonds consists ofKinds of bondsForces between bonds

Macroscopic - Observed with sensesMicroscopic Not observed with senses

A mixture is when two or more substances are combined, but each of the substances keep its original properties.Mixtures

Properties of mixturesThe substances keep their original properties.

The substances dont have to be mixed in a fixed ratio.

The mixture can be separated with simple methods.

Two mixturesThe substances are all in one phaseEg airYou cannot identify the different components of the mixture.There are more than one phase.Eg sand and waterSuspension solids that float in liquids. Eg muddy waterEmulsion steady mix of insoluble substances in a liquid.Eg milk, mayonnaise

HomogenousHeterogenous

Because mixtures retain the original properties, we can separate the different substances by physical methodsSeparation methods

Homogenous separation Evaporation

Distillation

Fractional distillation

Chromatography

Centrifugation

Evaporation

Distillation

Taken from regentsprep.orgChromatography

Taken from faqs.orgCentrifuge

Heterogenous separationFiltration

Separating funnel

Decanting

Sorting

Sieving

Separating funnel

Filtration

Taken from codeunit.co.zaSorting

Taken from sbs.utexas.eduSieving

Pure substances are made of only one substance or a compound. Pure substance

Pure substancesAn element only consists of the same atoms.An element cant be separated into simpler substances.Elements are categorised as metals, non-metals and semi-metals.A compound consist of two or more different elements bonded together. Can only be separated by chemical methods.Compounds properties differ from the individual elements.Joined in fixed ratios.Chemical reactions occur during formation.ElementsCompounds

Periodic table

FormulaeH2O is the formula of water

H2O

2 hydrogen atoms 1 oxygen atom

CaO, CaSO4, Ca(OH)2, NH4NO3, CO2, NH3

Diatomic molecules

Ionic bonds

OHH

Ionic bondsGroup 1, 2, 6, 7

Transition metals give off 1, 2, or 3 electrons

Mono-atomic anion ide

Polyatomic ion/radical

Physical differencesMetallic lustreElectrical conductorsThermal conductorsOpaqueMalleable and ductileSolids @ room temperature, except HgHigh MP and BPDull (except graphite & diamonds)Poor electrical and thermal conductorsSome solids = opaque, gases are translucentSolids = brittleLow MP and BPMetalsNon-metals

Semi-metalsGenerally have properties of metals, but a few non-metal properties as well.Ability to conduct electricity increases with heat. (in contrast with metals)

Properties of semi-metalsShiny or dull

Conduct heat and electricity better than non-metals, but weaker that metals

When heated, they can conduct electricity better.

Electrical conductors, Semi-conductors and insulatorsMetals conductors

Non-metals insulators

Semi-metals poor conductors, called semi-conductors

Thermal conductors or insulatorsThermal conduction is the flow of heat from a high temperature to a low temperature.

Metals thermal conductors

Non-metals thermal insulators. All materials that trap air = poor conductors, because air is a poor conductor.

Magnetic and non-magnetic materialsFerromagnetic elements strongly attracted to magnetsFe, Ni, Co, Alnico, ceramic (insulating magnets), magnetite

Phases of matterAnd the kinetic molecular theory

The three phases of matter

SOLIDS

Solids keep its shape and can only be dented, broken or bent.HardHigh densityNo compressibilityFixed volume

Made up of small particlesVibrate onlyVery small spaces between particlesStrong attractive forces causes specific shapeNo diffusionHave crystalline structureHave a specific melting point

Liquid

MeltingSolidification

LIQUIDS

No fixed formNot hardHigh densityNo compressibilityFlowsFixed volume

Particles move in ordered fashionCollisions occurDiffusion occurSmaller spaces between particles than with gasesExerts pressure in all directionsWeak force between particlesSpecific freezing point and boiling point

Gas

EvaporationCondensation

GASES

No fixed formNot hardLow densityEasily compressibleFlowsNo fixed volume

Particles move fastGreater collisionBig open spacesWeak/no forces between particlesInvoluntary motionDiffusion occursExerts pressure in all directions

Kinetic model of matter

Motion of particles

Diffusion

is the movement of particles from a high concentration to a low concentration.

Motion of particles

Kinetic model of matter

1. All matter consist of small particles2. Particles are in constant motion3. Spaces between the particles4. Constant collisions between particles and container5. Temperature is a measure of the kinetic energy of the particles6. Forces between particles7. Phase changes occur when energy changes occur

Phase changes

1. Condensation

4. Evaporation

3. Melting

2. Solidification

1. Condensation

Prior to condensation:* particles slow down* not far apart* less violent collisions

Phase change follows:* Spaces decrease* Forces increase* more orderly arrangement

2. Solidification

Prior to solidification:* particles move very slowly* particles very close to each other* only vibrates

Phase change follows:* very small spaces between particles* forces between particles become very strong* orderly arrangement

3. Melting

Prior to melting:* particles move fast* particles further apart

Phase change follows:* spaces increase* forces decrease* less orderly arrangement

4. Evaporation

Prior to evaporation* particles move very fast* particles very far apart* violent collisions due to high speed

Phase change follows:* spaces between particles are big* forces negligible* disorderly arrangement

Evaporation vs. boiling

EVAPORATION

Occurs @ temp below B.P.

Occurs only on surface

Slow

Causes cooling heat absorbed from environment

BOILING

Occurs @ B.P.

Occurs throughout the liquid

Quicker

Temp remains constant during boiling

Heating curve of water

Heating curve of water

Atomic structureAtomic models

The electrical nature of matter

Michael Faraday

Electrical current through salt solutions

Amount of Q = amount of atoms reacting

Dalton's atomic theory

Michael Faraday

Amount of Q = amount of atoms reacting

Thomsons atomic model

Charge and mass of electrons of all substances are the same.

Thus, electrons in all substances must be the same.

Substances differ because electrons are arranged differently.

-----

Rutherfords atomic model

Bombard thin gold foil with -particles (heavyweight kind of radioactivity).

Fluorecent zinc sulphide screen opposite foil = -particle detector. fluorecent zinc sulphide screen

-particles gold foil

Radioactive source

Rutherford continued

Observations

Most of the -particles showed no diversion. Some were deflected

Some were reflected

ConclusionsElectrons occupy the greatest volume of the atom.

Positive particles are grouped together in the nucleus very heavy, but small.

Atom

++++++++++++++ (+2)

Assumptions

The positive charges are all together in a small volume in the nucleus.

The nucleus is surrounded by a space that contains the e- (v. Small mass) e- are responsible for the great volume of an atom.

Mass is concentrated in the nucleus.

Later investigations predicted that the nucleus ispositively charged. # Protons = # electrons. e- dont move like bees around a hive, e- would collapse into nucleus.

Bohrs atomic model

Electrons move in orbits

Electrons with the same energy move around in the same orbit

Electrons in orbits further away from nucleus have a higher energy

Planetary atomic model

e- move in energy levels

e- with same E values, move in same E levels

Valence orbitals have higher energy than those close to the nucleus

Energy levels closer to the nucleus are filled first with e-

Each energy level can only take a specific amount of e-

e- in orbits close to the nucleus are lower in energy level than orbits further away

If e- are in lowest possible energy level ground state

When e- absorb energy it rises in energy level.

This (excited) state is unstable and e- fall back to lower energy levels

Line spectra

Electrons in the ground state absorb energy. Electrons are now excited, and move to a higher energy level.

This electron is now unstable.

It falls back to its ground state, radiating extra energy as light.

The separate coloured lines of light show electrons only have certain energy. Electrons energy is thus quantised.

Each element has its own unique line spectrum.

Line spectra occur when gases are heated of an electric current is passed through it.

Wave mechanical atomic model

Bohrs atomic model explains the structure of hydrogen, but not those of atoms with more than one electron.

The discovery of wave properties of electrons gave us a more acceptable model.

e- have both particle and wave properties.

Schrodinger stated that moving e- form a 3D wave space that surrounds the nucleus, called an orbital.

Neutron

J. Chadwick discovered a particle with a mass nearly equal to the proton.

Neutral charges, called neutrons.

Atomic mass and diameter

Atoms are extremely small with small masses.

Diameters are also extremely small. Most of the volume of an atom is empty space, the nucleus accounts for most of the mass of an atom at the centre.

ELEMENTAVG ATOMIC MASS

Hydrogen1,673 55 X 10 -27

Carbon1,994 36 X 10 -26

Oxygen2,656 59 X 10 -26

Uranium3,952 33 X 10 -25

Relative atomic mass

Hydrogen is the lightest atom and is chosen as the standard for an atomic mass scale.This mass is equal to 1.Using proportion to find the atomic masses of other elements relative to a mass of 1.

1,673 55 X 10 -27 kg of Hydrogen = 1 on the Hydrogen scaleSo, 2,656 59 X 10 -26 of oxygen = 1x2,656 59 X 10 -26 kg 1,673 55 X 10 -27 kg = 15, 87 on the Hydrogen scale

Structure of the atom

The atom consists of very many small subatomic particles. In chemistry we work with protons, neutrons and electrons.Protons and neutrons are in the nucleus at the centre.Electrons occupy a large region around the nucleus and are 1836 times lighter.When electrons and protons are equal in number, the atom is neutral.When an electron is removed, the atom will be positively charged. An ion is an atom that has a charge on it. Cations are positively charged atoms.Anions are negatively atoms.

Isotopes

Same element, different masses and amount of neutrons.

Nuclide = isotopic nuclei.

Isotopes

Carbon (atomic # 6) has three natural isotopes with atomic weights of 12, 13 and 14.

isotope#p#n========== C-1266 C-1367 C-1468

Tin (Sn, atomic # 50) has ten natural isotopes with atomic masses of 112, 114, 115, 116, 117, 118, 119, 120, 122 and 124. How many protons and neutrons do these isotopes have?

Radioactive or Stable?

Radioactivity is a nuclear phenomenon: it comes as a result of a particular structure in a nucleus.

A radioactive atom is considered unstable. All unstable atoms emit radioactivity (usually by ejecting nuclear particles) in order to reach a stable configuration. This is the process of radioactive decay

So, not all atoms will be radioactive, just a small proportion of isotopes with unstable nuclei. The bulk of isotopes are stable, or non-radioactive.

Stable and Radioactive Isotopes

Carbon (atomic # 6) has three natural isotopes with atomic weights of 12, 13 and 14.

isotope#p#n========== C-1266 C-1367

C-14 is a radioactive isotope; C-12 and C-13 are stable.

Over time the proportion of C-12/C-14 and C-13/C-14 will increase until there is no C-14. (unless some process makes new C-14...)

C-1468

Radioactivity Inside You

Concerned about radioactivity in nature?

To keep things in perspective, consider that 0.01% of all potassium is radioactive K-40.

Potassium is an essential element in the human body. If your body is about 1% K, this means a 70 kg (150 pound) person contains around 1x1021 atoms (thats one billion trillion atoms)of radioactive K-40.

Energy levels in an atom

Energy of an atom is quantized, meaning your electrons all have discrete amounts of energy.Electrons are thus limited to a specific energy level,Which you learned in grade 8 was an orbital.

These main energy levels are indicated by n, and1, 2, or 3 following it.

eg. n = 1

Energy levels in an atom

Each of these main energy levels are then sub-divided into sub-energy levels, which are indicated by the numbers s, p, d and f.

s