Chemistry

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Key Words

Atoms- Smallest part of an element which still behaves as that element
Molecule- A fixed no. of atoms joined by covalent bonds
Element- One substance
Compound- 2 elements chemically combined
Mixture- 2 or more elements not chemically combined
Pure- only one substance present
Protons- Atoms that are positively charged
Electrons- Atoms that are negatively charged
Neutrons- Atoms with no charge
Groups- The columns
Periods- The rows
Ionic Bonding-Strong electrostatic force of attraction between oppositely charged ions 
Diagram: Atom and table 

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Bonds

Ionic- Metal + Non-Metal


Covalent- Non- Metal + Non-Metal


 
Metallic- Metal + Metal 

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Covalent structures

1) Simple:
>Only a small no. of atoms are covalently bonded to form molecules

>Water as a liquid


>Water as a gas

Properties:
1)Low BP + MP (Weak forces)
2)Insoluble with water unless they react (doesn't dissolve)
3)Soluble in organic solvents made from carbons and hydrogens
4)No overall charge on the molecule= don't conduct electricity

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Covalent structures

2)Giant covalent structures
Diamonds:

-Tetrehedral  arangement
-all 4 outer electrons on each c atom
-not a fixed no. of c atoms - huge no. of cov bonds

Properties:
1)Very hard
2)High MP and BP (large no. of cov bonds)
3)Cannot conduct electricity because there are no free electrons
4) Insoluble

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Covalent structures

Graphite:

 

>Hexagon and layer arrangement
>Only 3/4 electons in each c atom are involved
>strong cov bands but weak forced inbetween layers (slide past eachother)

Properties:
1)Slimy feeling
2)High MP + BP
3)Insoluble
4)Can conduct 

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Metallic Bonding

Diagram- Sodium atoms and Sodium ions

Bonded together by a sea of delocalised electrons
Physical Properties;
1)Conduct heat+ elec
2)High BP + MP
3)Strong and Malleable and Ductile
4) Opaque

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Diffusion

Natural mixing of particles in a liquid/gas (no external forces)
E.g.Diagram of ammonia chloride 

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Structure of an element in the periodic table

Diagram:

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Formation of Ions

> formed by a loss/gain of electrons
> If an atom loses elecrtrons a positive ion is formed
> If an atom gains electrons a negative ion is formed
OIL RIG

When drawing an ION:
1) Square brackets
2)Charge 

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Testing salts for Cations

SODIUM HYDROXIDE SOLUTION
Li+ RED

Na+ ORANGE
K+ LILAC
CA 2+ BRICK RED 

Ammonium- Damp red litmus paper- changes blue= alkali
Copper- Blue precipitate
Iron(II)- Green precipitate
Iron(III)-Red/brown precipitate 

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Testing salts for anions

ADDING NITRIC ACID AND SILVER NITRATE SOLUTION

Chloride= White precipitate
Bromide= Cream precipitate
Iodide= Yellow precipitate

ADDING ACID AND THEN TESTING GAS EVOLVED WITH LIMEWATER

This tests for carbonate. The Gas given off is Carbon dioxide it turns limewater cloudy

ADDING BARIUM CHLORIDE

Tests for sulfate ions. Produce a white precipitate if sulfate ions are present 

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Gas Tests

Hydrogen:
Test- Lit splint
Result- Goes out with a squeaky pop
Oxygen:
Test-Glowing splint
Result- Relights
Carbon Dioxide:
Test-Bubble into limewater (calcium hydroxide solution)
Result- Turns milky
Ammonia:
Test- Damp red litmus paper
Result- Blue
Chlorine:
Test-Damp blue litmus paper
Result- Bleached white 

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Hydrocarbons (ALKANES) single bonds

>

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Fractional Distillation of Crude Oil

1) Heat crude oil
2) Pass vapour into fractionating tower
3)Tower is hotter at the bottom than top
4) Fractions have different boiling points
5) Different fractions come off at different heights (Lower BP condense nearer top) 

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Fractions from fractionating tower

Fractional distillation>diagram:

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Cracking

When crude oil is distilled it produces lots of unuseful fractions(long chains)
>Thick, vicous liquids
>Have higher boiling points
>Not very flammable=not good fuels

CATALYTIC CRACKING IS A WAY TO CONVERT LESS USEFUL LONG CHAIN ALKANES INTO MORE USEFUL SHORT CHAIN AND LIGHTER ALKANES. 

Industrial cracking uses a catalyst of silicone dioxide/ aluminium oxide
Heated to a high temp (600-700 deg.)
TYPE OF REACTION: THERMAL DECOMPOSTION 

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Isomers

An isomer has
1) The same molecular formula as another molecule but
2)The atoms are arranged in different ways

E.g)  

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Combustion of alkanes

Complete combustion:
PLENTIFUL SUPPLY OF OXYGEN
Products are water + carbon dioxide
E.g)

Incomplete combustion: TOXIC
LIMITED SUPPLY OF OXYGEN
Products are water and carbon monoxide
E.g)

GAS:

SOLID: 

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Alkenes

Formed from cracking long chain alkanes

 

Test: Add Bromine Water- from orange to colourless 

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Addition Polymerization

Monomer- A small molecule that joins together with many other small molecules to form one large polymer

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Naming Polymers

>

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Thermoplastics and thermosetting plastics

Diagrams>

 

Polyethene is flexible= forces between the polymer molecules are strong enough to be a solid but weak enough to move

Bakelite= Bonds between chains are strong so they cannot move/slip over eachother 

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The effect of concentration

Equation:

Graph sketch

Variables kept the same- Same apparatus, same volume of liquids, same mass of calcium carbonate, same sized marble chips,same temp', started stop watch at same time 

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Collision Theory

Reactions occur when particles collide
Not all collisions lead to a reaction
Only successful collisions lead to reactions (particles hit eachother head on with sufficient energy)
Minimum energy particles must have is called activation energy
The more successful collisions the faster the reaction
If marble chips are added to hydrochloric acid>

Acid particles collide with surface of the marble chips: Diagram shows the same mass...

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Rates Summary

Surface area of solid: Increases the rate of reaction, the smaller the pieces the larger the surface area- More solid reactant particles can come into contact with liquid/gas reactant

Concentration of solution or pressure of gas: As concentration increases the rate increases- higher concen means there are more particles in the space, more successful collisions

Temp':Higher the temp' the faster the rate of the reaction- Increases kinetic energy of the particles, more successfulcollisions

Add a catalyst: Increase rate of reaction- The activation energy is lower beacuse an alternative pathway is provided by the catalyst 

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Disappearing cross reaction

Equation:

Sulfur precipitate forms and eventually obscures the X

Sketch of the graph: 

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Catalysts

Substance that speeds up reactions- catalyst itself remains unchanged at the end

Provides an alternative route for the reaction which has a lower activation energy

Equation for rate of reaction: 

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Periodic Table: Properties of Halogens

>Table

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Properties of alkali metals

Table>

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Heating metals and non-metals in air

What does the surface of the lithium look like when it has been cut?
Shiny
When left exposed to air?
Dull
Why does it burn with an orange flame?
-Oil 
Results 

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Why elements in the same g have sim chem proper

The elements in a group have the same number of outer electrons (outer shell)

It is outer electrons that are involved in chemical reactions

The electrons are either shared (to make covalent bonds) OR transferred (forming ions that then form ionic bonds) to achieve full outer shells of electrons, which makes them more stable 

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The Noble gases (group 0)

Helium:
-Aircraft fuel            +Not dense
-Air balloons          + Not soluble

Neon:
-Advertising signs            +Visibility
-Fluorescent lamps         + Penetrate fog

Elements in noble gases have full outer shells so they are unreactive meaning they are more stable. Don't react with other elements.

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Reactions of alkali metals with cold water

Sodium, Na

Lithium, Li

Potassium, K 

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Halogens (group 7)

>

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Displacement reactions between met + met salts

>

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Rusting

Conditions under which iron rusts:
1) Water
2)Oxygen

Rust preventions;
1)Oil/grease
2)Paint
3)Galvorising(protective layer of zinc) C

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Chemistry of astatine

Solid
At
Non-Metal
Coloured vapour

Sodium-Ionic
Aluminium-Ionic
Sulfur- Covalent

Astatide ions? At
Which is more reactive?
Iodine- reactiivity decreases as you go down the group 

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Ions

>

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