Atomic Structure

Atoms are made of three different sub atomic-particles:

Protons (p)

Neutrons (n)

Electrons (e)

Protons and neutrons are known as nucleons, as they are tightly packed together at the centre of the atom, forming the nucleus. Electrons move rapidly around the nucleus. 

Protons:

- Carries one positive electric charge (+1)

- Has a relative mass symbol of 1 

Neutrons

- Carries no electric charge

- Has a relative mass of 1

Electrons:

- Carries one negative electric charge (-1)

- Has a relative mass of 1/1840 (negligible)

All atoms are electrically neutral. An atom contains an equal number of positively charged protons and negatively charged electrons. They cancel out exactly.

The number of protons in a number is called the proton number or the atomic number. The atomic number is represented by the symbol Z. Also, the atomic number shows how many electrons are in an atom too. 

The total number of protons and neutrons in an atom is called the nucleon number or the mass number. The mass number is represented by the symbol A. The mass of an atom depends on the number of protons and nucleons in the atom's nucleus. The mass of an electron is negligible.

The atomic and mass numbers can be included when representing an element in symbols. The atomic number is in subscript (below), left of the symbol. The mass number is in superscript (above), left of the symbol. For convenience, the element can be represented using only the mass number. E.g.: Sodium-23 or ²³Na. 

Nucleon number > No. of protons and neutrons (relative atomic mass)

Atomic number > No. of protons/ No. of electrons

Ions > Formed when e-s are lost/ gained

Kinetic Particle Theory

Why are gases able to be compressed but not liquids or solids?

The molecules in a gas are far apart from each other in a random arrangement  unlike liquids where the molecules are packed together but not in a orderly arrangement, which can still move around a bit, and solids, where the molecules are closely packed into an orderly arrangement and they can only vibrate in their fixed positions, therefore gas molecules can move freely and can be compressed into the spaces between them.

Why do gases and liquids take the shape of their containers but not solids?

The molecules in a solid are closely packed in an orderly arrangement, thus allowing them to only vibrate in their fixed positions. However, the molecules in a liquid and solid still allow movement for the molecules and so they can take the shape of their containers.

How do particles look in solid vs liquid vs gaseous? Observe its distances and kinetic energy.

The particles in a solid are packed closely together, so there is very little kinetic energy. The particles in a liquid are packed together but not in an orderly arrangement, so there is more kinetic energy than a solid. The particles in a gas are far apart from each other, so there is the most kinetic energy.

Kinetic Particle Theory

Substances can exist as different physical states, and change from one physical states to another. At different states, the particles have different kinetic energy. Compared to solids, liquids have particles with greater kinetic energy.

A solid has high density. A liquid has a higher density than gas but a lower density than solid. A gas has low density.

A Solid:

Cannot be compressed

Has a fixed volume

Has a fixed shape

High Density

A Liquid:

Cannot be compressed

Has a fixed volume

Has no fixed shape

Higher Density than Gas, but lower than Solid

Therefore, a solid's particles are packed together closely in an orderly arrangement. They are held to together by forces of attraction. They are able to vibrate about their fixed positions but are not free to mover amongst each other.

A liquid's particles are packed to together quite close together but not in an orderly arrangement. They are held together by forces of attraction. They have more energy than solids. They are able to move by rolling and gliding.

A gas' particles are far apart from each other in a random arrangement. 

Kinetic Particle Theory

1) States of Matter

Solid- Fixed Shape, Fixed Volume, Cannot be compressed

Liquid- Not Fixed Shape, Fixed Volume, Cannot be compressed

Gas- Not Fixed Shape, Not fixed Volume, Can be compressed

2) Kinetic Particle Theory

The Kinetic Particle Theory states that all matter is made up of tiny particles and that these particles are in constant, random motion. Moving particles have kinetic energy, thus the name kinetic particle theory.

The Kinetic Particle Theory:

1) Describes the states of matter

2) Explains the differences in the properties of solids, liquids and gases

3) Explains the change of state 

Example:

Air is made up of tiny dust particles that move around. The dust seen in a beam of light is the result of air particles moving and bumping into dust. Air particles are too small to be seen by the naked eye, therefore we can only see the due moving.

Separation

Decanting:
The simplest way to separate a dense, soluble solid from a liquid is to just pour the liquid away.
E.g.: Removing pebbles from water.

Filtration (Liquid + Solid):
To remove small solid particles from a liquid. The filter paper acts as a sieve and the liquid can pass through the pros of the filter paper but the solid cannot do so.
E.g: Sand, clay, dust, precipitates.
To separate lead (II) sulphate from a reaction mixture:
1) Prepare the lead (II) sulphate.
2) Fold the filter paper.
3) Collect the residue in the folded filter paper.
4) Filter the mixture.

Evaporation to Dryness and Crystallisation:
Distillation- Evaporation and Condensation
Based on the compounds' boiling points.  To separate substances which have been dissolved to form solutions. We evaporate water from the solution.
E.g.: We evaporate salt solution to dryness.
Crystallization
Crystallization makes a solution pure. Solution should be saturated and to obtain the pure substance from its solution. (change of state )
Aqueous (aq)= to solid
However, many substances decompose when they are heated strongly. In crystallisation, water is removed by heating the solution and stops when a hot saturated solution is formed. After it cools to room temperature, the dissolved solid will be formed as pure crystals.
A glass rod can be used to test if a solution is saturated. It is dipped into a solution and removed. If, when cooling, small crystals form on the rod, than the solution is saturated. This is also the solution's saturation point or crystallisation point.
E.g.: Sugar
To obtain copper(II) sulphate crystals from copper(II) sulphate solution.
1) Heat the copper(II) sulphate solution until the solution is saturated.
2) Allow the saturated copper(II) sulphate solution to cool.
3) Filter the copper(II) sulphate crystals and solution to cool.
4) Copper(II) sulphate crystals are obtained.

Filtration (Solid + Solid):
To separate a mixture of two solids if one of them is soluble in a solvent but the other is not. To differentiate between differently-sized substances.
E.g.: Salt and sand
To separate a mixture of common table salt and sand:
1) Pour some distilled water into the mixture of common table salt and sand. Stir and warm the mixture.
2) Pour the warm mixture into a filter funnel lined with filter paper. Collect the filtrate in a conical flask.
3) Wash the residue with a little distilled water to remove all the salt solution from it. The residue is sand.
4) Pour the filtrate into an evaporating dish and evaporate the filtrate to dryness. The white solid left in the evaporating dish is salt.

Magnet:
To separate a mixture of two solids if one of them is magnetic but the other is not.
E.g.: Separate iron from sulphur

Sublimation:
To separate a mixture of two solids if one of them sublimes and the other has a high melting point. One solid sublimes to the gaseous state. If it reaches a cold surface, it will condense.
E.g.: Sublimes: Iodine or ammonium chloride
High melting point: Sand or sodium chloride

Purification and Chromatography

A pure substance:
- Is made up of only one substance
- Is not mixed with another substance
- Can be determined by checking its melting and boiling point, or by using chromatography

- Has an exact and constant melting point.
- Will melt at completely at one temperature, if it is a solid
- The greater the amount of impurities, the lower the melting point
- Has an exact and constant boiling point
- The greater the amount of impurities, the higher the boiling point of the liquid

Chromatography:
It is the technique of using a solvent to separate a mixture into its compounds.
It is used to:
- Separate the components in a sample.
- Identify the number of components in a sample.
- Identify the components present in a sample.
- Determine whether a sample is pure.
It depends on solubility of compounds or substances in a solvent.

1) A spot of food coloring is applied to the chromatography paper.
2) Once the paper is dipped into the solvent, ethanol, it souls up the ethanol.
3) Ethanol dissolves the dye. It continues to travel up the paper, carrying the dyes along.
4) A dye that is not very soluble in ethanol will be carried far along the paper.
5) A dye that is very soluble in ethanol will be carried far along the paper.
6) Colored spots are left in different places on the paper at the end of the experiment.
A pure sample gives only one spot on the paper.

Rƒ+= Distance travelled by the substance ÷ distance travelled by the solvent

Example: The Chalk Experiment
The slower it moves up the chalk, the less soluble it is. (Green)
The faster it moves up the chalk, the more soluble it is. (Red)
As it is highly soluble in water, the red ink prefers to stay in water and will travel up the chalk with the water.
As it is less soluble, the red ink will prefer to stay on the chalk and will not move up as quickly with the water level.

Crude oil

Fractional Distillation of Crude Oil
Petroleum refining is the process of separating the many compounds present in crude petroleum. The principle which is used is that the longer the carbon chain, the higher the temperature at which the compounds will boil. The crude petroleum is heated and changed into a gas. The gases are passed through a distillation column which becomes cooler as the height increases. When a compound in the gaseous state cools below its boiling point, it condenses into a liquid. The liquids may be drawn off the distilling column at various heights.