Chemistry Unit 2

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Ionic bonding

Forms Giant Covalent  regular Lattice

Strong electrostatic attraction

High Melting/Boiling points

Conductors of electricity when :

 - Molten

 - In solution

Forms with metals + non-metals

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Covalent Bonding

1. Simple Molecular

Strong covalent bonds

Small molecules

Weak forces of attraction

Low Melting/boiling points

Poor conductor of electricity - no ions

2. Giant Covalent

Strong bonds

High Melting/Boiling points

Do not conduct electricity

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Giant Covalent structures

1. Diamond

4 covalent bonds on each atom --> rigid structure

2. Graphite

Each atom has 3 bonds 

Layers can slide --> soft

Weak intermolecular forces between layers

One delocalised electron on each atom

Good conductor of electricity and heat

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Metallic Structures

Giant structure

Delocalised electrons from the outer shell of every metal atom

Good conductor of electricity/heat

Strong electrostatic attraction between positive ions and electrons

Regular structure

Layers can slide --> malleable

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Nanoparticle = 1-100 nanometres across

Only a few hundred atoms

Uses :


Stronger, lighter building materials


Computer chips - conductors of electricity

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Thermosoftening Polymers :

Weak intermolecular forces

Free to slide over eachother

No cross links

Easy to melt - can remould

Thermosetting Polymers :

Strong intermolecular forces with cross links

Do not soften when heated

Strong hard and rigid

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Gas Chromatography

1. Sample is injected as a gas

2. Carrier gas moves sample through solid in column

3. Substances move through at different speeds and are separated

4. The detector shows the retention time

This can be linked to a Mass Spectrometer

This is under a vacuum to stop molecules colliding

1. Sample is ionised

2. Sample put through magnetic field to separate it

3. A Spectra is produced

This tells you the relative formula mass of the compound

Mr = peak with highest mass

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Chemical Analysis

Adding NaOH

Iron II          - Green Precipitate

Aluminium  - White Precipitate        Redissolves in excess NaOH

Iron III        - Brown Precipitate

Copper       - Blue Precipitate

Calcium      - White Precipitate

Magnesium - White Precipitate

Adding AgNO3

Chlorine  - White Precipitate

Bromine  - Cream colour

Iodine     - Yellow colour

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Chemical Analysis 2

Flame Test :

Lithium       - Crimson

Sodium      - Yellow

Potassium  - Lilac

Calcium     - Red

Barium      - Green

Copper     - Blue / Green

SO4 test :

Add HCl and sodium sulphate and add to water and add Barium Chloride - Acid + white precipitate

CO3 test :

Add to HCl, collcet gas and bubble it through limewater - White precipitate

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Neutralisation Reactions

Acid + Metal --> Salt + Hydrogen

Acid + Metal Oxide → Salt + Water

Acid + Metal Hydroxide → Salt + Water

Acid + Alkali --> Salt + Water

Ammonia + Acid makes a fertiliser

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