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Elements, Compounds & MixturesIntroductory Chemistry

States of MatterProperties of Solids, Liquids & GasesChanges of State cycleParticle Theory

Eternal QuestionsPeople have long asked:

What is the world made of?

Le Penseur (The Thinker) - Auguste Rodin

Particle TheoryScientists have come to realize that the matter of the world is made from a few fundamental building blocks of nature.

The word"fundamental"is key here. By fundamental building blocks we mean objects that are simple and structure-less-- not made of anything smaller.

The particle theory says;

that all matter consists of many, very small particles The particles are constantly moving (they have kinetic energy) or in a continual state of motion.The higher the temperature, the faster the particles moveThe differences between solids, liquids and gases can be explained by this theory.

Properties of SolidsIn a solid, particles of matter are packed closely together and are not free to move about within the substance.

Motion for the particles in a solid is confined to very small vibrations of the atoms around their fixed positions; therefore, solids have a fixed shape that is difficult to change. Solids also have a definite volume; that is, they keep their size no matter how you try to change them.

Properties of LiquidsThe particles in a liquid are attracted to each other; however, liquid particles have more space between them, so they are not fixed in position.

The attraction between the particles in a liquid keeps the volume of the liquid constant.

Liquids will flow and fill the lowest portion of a container, taking on the shape of the container but not changing in volume.The limited amount of space between particles means that liquids have only very limited compressibility.

Properties of GasesGas particles have a great deal of space between them and if unconfined, the particles of a gas will spread out indefinitely; if confined, the gas will expand to fill its container.

When a gas is put under pressure by reducing the volume of the container, the space between particles is reduced, and the pressure exerted by their collisions increases.

If the volume of the container is held constant, but the temperature of the gas increases, then the pressure will also increase.

Gas has no definite volume and no definite shape.

Changing State Diagram

Getting SmallerAtomsThe Periodic TableAtomic Number (Z)Groups & PeriodsNoble GasesMetals, Non-Metals, Metalloids

AtomsBy convention there is colour,By convention sweetness,By convention bitterness,But in reality there are atoms and space.- Democritus (c. 400 BCE)

Everything in the world is made up of small parts.

Atoms?There are about 100 types of atoms.

Each different type is called an element.

Each element has a symbol and a name.

For example the 8th smallest element is called Oxygen.Its symbol is O

ElementsElements are only made up of one type of atom.

Everything else is made up of combinations of different atoms.

Whats in an atom?An atom is made up of three parts.

All of the mass is concentrated in the nucleus in the middle. The nucleus makes up almost all of the mass of the atom.

The nucleus is made up of positively charged protons and neutrons of no charge.

The number of protons tell us which element it is.

This has 7 protons so it is Nitrogen.

ElectronsOutside the nucleus there are rings of electrons.

There are the same number of electrons as protons but with the opposite charge (negative).

Electrons dont really weigh anything.

So..In reality, the electrons are very far from the nucleus.

If the nucleus was the size of a sugar cube in the centre of the MCG, the electrons would be as distant as the outermost seats.

If the nucleus was the size of a soccer ball, the electrons would be 20 kilometres away.

RutherfordA New Zealander found this out by firing radiation at a thin piece of gold.

He discovered that most of an atom is EMPTY SPACE.

YOU are made of atoms.

YOU ARE MOSTLY EMPTY SPACE.

Since, all of the atoms from Earth are from extinct stars

YOU ARE MOSTLY EMPTY SPACE AND THE BIT THAT IS HERE IS FROM AN EXTINCT STAR

IN FACT, IF YOU SQUISHED OUT ALL OF THE EMPTY SPACE FROM ALL OF THE PEOPLE ON EARTH, THE AMOUNT THAT WEIGHS ANYTHING (THE NUCLEI) WOULD BE THE SIZE OF A GRAIN OF RICE.

FREAKY.

AtomsAn atom is the smallest particle of a chemical element that can exist.

An atom consists of a nucleus at the centre, surrounded by a cloud of one or more electrons.

The nucleus is made up of protons and neutrons

Protons are positively charged particles

Neutrons have no charge (are neutral)

Inside the Atom

Is mostly empty space!

The Periodic Table

Dmitri Mendeleev (1834 1907)

Atomic Number - HistoryThe first attempts at constructing a Periodic Table listed atoms in order of their atomic weight each atom was thus given an atomic number.

In 1911, Ernest Rutherford, Niels Bohr and Antonius van der Broek suggested that this could be improved by ordering them based upon the charge of their nucleus.

In 1920, Rutherford discovered protons which were shown to match exactly with the atomic number.

The symbol for atomic number, Z, comes from the German word Atomzahl, meaning atomic number.

Atomic NumberIn modern chemistry, the atomic number of an atom is designated by the letter Z.

The atomic number of an element matches the number of protons within the nucleus.

For example:

Groups & PeriodsThe periodic table has rows called periods - and columns called groups - and each of these specific characteristics.

Elements in the same group share similar chemical characteristics.

Elements in the same period have the same number of orbitals (layers of electrons circling the nucleus).

Noble Gases

The happy elements in Group 18

Noble gases have full outer shells of electrons so they are not chemically reactive, they are inert.

Helium has 2 electrons in its outer shell, Neon has 8

Metals, Non-Metals, Metalloids..Differences across the table.

MetalsMetals have several features in common:

They are solid at room temperature, except for mercury which is a liquid.

They can be polished to produce a high shine orlustre.

They are goodconductorsof electricity and heat.

They can all be beaten or bent into a variety of shapes. We say they aremalleable.

They can be made into a wire. We say they areductile.

They usually melt at high temperatures. Mercury, which melts at 40 C, is one exception.

Non-metalsOnly 22 of the elements are non-metals. At room temperature, eleven of them are gases, ten are solid and one is liquid. The solid non-metals have most of the following features in common:

They cannot be polished to give a shine like metals; they are usually dull or glassy.

They arebrittle, which means they shatter when they are hit.

They cannot be bent into shape.

They are usually poor conductors of electricity and heat.

They usually melt at relatively low temperatures.

Many of the non-metals are gases at room temperature.

MetalloidsSome of the elements in the non-metal group look like metals. One example is silicon.

While it can be polished like a metal, silicon is a poor conductor of heat and electricity and cannot be bent or made into wire.

Elements that have some features of both metals and non-metals are called metalloids.

There are eight metalloids altogether: boron, silicon, germanium, arsenic, antimony, tellurium, polonium andastatine.

Uses for Metals Based on their PropertiesCopper is ductile & conducts electricity very well, hence its use in electrical wiring.

Iron is strong & malleable, which makes it perfect for large construction. When combined with other metal & non-metal elements (called an alloy) it becomes an ideal construction material.

Steel is an alloy of carbon & iron.

The lustre of metals has also seen their use in many forms of jewellery.

Uses for Non-Metals based on their propertiesNon-metals also have extensive uses. Solid carbon, when exposed to extreme pressure, creates diamonds.

Neon gas is inert so it doesnt react it just glows red/orange in a vacuum discharge tube, creating the ubiquitous Neon Signs.

Silicon is used in integrated circuits because of its low conductivity to electricity & heat (silicon is called a semiconductor). This property enabled modern computers to exist.

Compounds & Mixtures

SortingAll substances can be organised into one of three categories;

Elements contain only one type of atom. Few things around us exist purely as elements.

Compounds (short for Compound Molecules) are made up of two or more elements bonded tightly together. They are usually very different from the elements that make them up.

Mixtures are made up of two or more elements, two or more compounds, or a combination of both.

MoleculesMoleculeis the general term used to describe any atoms that are connected bychemical bonds

Every combination of atoms is a molecule.

Simple:

Complex: Ridiculous:

Molecules can be atoms of just one Element

CompoundsWhen molecules include different atoms (elements) they are called compound molecules or just compounds.

CompoundsA compound molecule is a molecule made of atoms from different elements.

All compounds are molecules, but not all molecules are compounds.

Hydrogengas (H2) is a molecule, but not a compound because it is made of only one element.

Water (H2O) can be called a compound molecule because it is made of hydrogen (H) and oxygen (O) atoms

Mixturesa mixture:consists of two or more different elements and/or compounds physically intermingled,

can be separated into its components by physical means, and

- often retains many of the properties of its components.

Draw these!

Mixtures do not have official scientific names for example, air is just called air.

Compounds are named according to the different elements they are made of..

For example; carbon dioxide, iron oxide, sodium chloride.

Molecular FormulaeCompounds and molecules also have a formula - an abbreviated way of writing what they are made of.

Water: H20

Carbon Dioxide: CO2

Carbon monoxide: CO

Salt (sodium chloride): NaCl

This is why we ask you to learn the symbols for the first 20 elements! So in future years you can identify compound molecules

Similarities & DifferencesMixtureCompoundCompositionVariable composition you can vary the amount of each substance in a mixture.Definite composition you cannot vary the amount of each element in a compound.Joined or notThe different substances are not chemically joined together.The different elements are chemically joined together.PropertiesEach substance in the mixture keeps its own properties.The compound has properties different from the elements it contains.SeparationEach substance is easily separated from the mixture.It can only be separated into its elements using chemical reactions.ExamplesAir, sea water, most rocks.Water, carbon dioxide, magnesium oxide, sodium chloride.

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