Chemistry Module 1

MENDELEEV produced the Periodic Table 

Left gaps so people could discover new elements and to predict properties of unknown elements.

Group 1 Elements - 1 electron in outer shell

Group 2 Elements - 2 electrons in outer shell 

Group 3 Elements - 3 electrons in outer shell

Group 1 Elements - More reactive as you go down

Group 7 Elements (Halogens) - Less reactive as you go down

Atoms always have the same number of PROTONS (+) and Electrons (-) so the charges are balanced and the atom is neutral.

First Shell - 2 

Second Shell - 8

Third Shell - 8

For Example, 

23 (Number of particles in Nucleus [Neutrons + Protons])

Na (Sodium)

11 (Number of Protons and [Electrons]) 

Alkali Metal + Water = Hydroxide + Hydrogen     Alkali Metal + Oxygen = Hydroxide 

(Lithium + Water = Lithium Oxide + Hyrodgen)    Alkali Metal + Chlorine =  Metal Chloride 

Alkali Metals are:     (Lithium + Chlorine = Lithium Chloride [white powder])

- Soft

- Easy to cut 

- Fresh cut face is shiny

When they react with water they: (The further down the table you go, the 

Give off a gas  more reactive the metals were. This meant

Heat (Steam was given off)  that lithium was least reactive and 

Melt metal as it became smooth and round  potassium was most reactive)

Fluorine: F  9  2,7  Pale Yellow Gas  -220(Melting Point)  -188(Boiling Point) 

Chlorine: Cl 17 2,8,7 Green- Yellow Gas -101(Melting Point) -35(Boiling Point)

Bromine: Br 35 2,8,18,7 Red- Brown Liquid -7(Melting Point) 59(Boiling Point)

Iodine: I  53 2,8,18,18,7 Dark Grey Solid 114(Melting Point) 187(Boiling Point) 

Astatine: At  85 2,8,18,32,18,7 _______________________? It is very rare, not much is known about it.

The colour gets darker as you move down the group.

They all have low melting and boiling points and these get higher as you move down the group.

A SALT IS JUST THE ACID WITH THE HYDROGEN REPLACED BY A METAL,

Hydrochloric Acid - Chloride

Sulphuric Acid - Sulphate

Nitric Acid - Nitrate

Acid + Alkali = Salt + Water       (Sulphuric Acid + Aluminium Hydroxide = Aluminium Sulphate + Water)

Carbonate + Acid = Salt + CO2 + H20  (Calcium Carbonate + Sulphuric Acid = Calcium Sulphate + CO2 + H20)

Metal + Acid = Salt + Hydrogen       (Zinc + Sulphuric Acid = Zinc Sulphate + Hydrogen)

Base + Acid = Salt + Water        (Sodium Hydroxide + Hydrochloric Acid = Sodium Chloride + Water)

(A BASE IS AN ALKALI THAT DOES NOT DISSOLVE IN WATER)

In this experiment you use, a Bunsen burner, splint and you see what colour the compound appears.

Sodium - Yellow/Orange

Potassium - Lilac 

Copper - Green 

Strontium - Red

Lithium - Red

Take chloride, bromide and iodide solution and add a few drops of Silver Nitrate solution. 

Chloride - White

Bromide - Cream

Iodide- Yellow

Chlorine   Kills bacteria, bleaches,                          Purifying water, weed killers, 

                reactive and good oxidizing                    antiseptics and hydrochloric 

          agent.                                                      acid.

Iodine      Kills bacteria, sensitive                            preparation for antiseptics, use to 

               to light and antiseptic                               treat cuts, used in taking photographs.

Helium     Very light gas, not                                   Used in weather balloons, used in under

               flammable  water breathing apparatus.

Neon       It's a gas, gives off light Used in neon lights in advertising

      when mixed with electricity and art displays

Argon     It is unreactive and protects  Used to fill light bulbs and welding processes

       metals from oxidation

Exothermic - Gives off energy

   - When reaction has more energy released than from the                                                                        original bonds.

Endothermic - Takes in energy

     - When reaction takes more energy to break the bonds, that is released when new chemical                            bonds are formed

Precipitation - If you react two chemicals which are dissolved in water, if one of the                                                   products doesn't dissolve it forms as tiny particles which then sink to  the bottom. this is                                 precipitation.

Temperature 

• Increasing the temperature means atoms have more energy, they move faster, more successful collisions. Rate of reaction increases.
• As temperature increases the time for a reaction to take place decreases so the rate of reaction increases.

Concerntration

• Higher concentration means more atoms, so more collisions happy, so more successful collisions.
• As concentration increases the time for a reaction to take place decreases so the rate of reaction increases.

Surface Area

• Larger surface area means more chemicals touch one another, so more successful collisions. 
• As particle size increases, the time for a reaction to take place increases so the rate of reaction decreases. 

Concentration

• In more concentration chemical there are a greater number of molecules in any volume, so more collisions occur, so more effective collisions are likely. 

Temperature

• In a hotter chemical the molecules have more energy, so are moving faster. They collide more often and harder, so more of the collisions are effective.

Particle Size

• Effective collisions can only take place when the two chemicals are in contact with one another. If the pieces are large there is less surface area in contract, so less effective collisions. If the particles are small there is more surface area in contact, so more effective collisions.

Time

• As time goes on in a reaction, the more molecules will have already reacted. This means the number left to react decreases, so the concentration decreases which means rate decreases.

Using a Gas Syringe

• the reaction produces a gas
• The tube carries the gas up the syringe
• The gas pu8shes the plunger in the syringe
• You can measure how much gas is produced using a scale on the syringe.

Using a balance

• The reaction produces a gas
• The balance measures the weight of the chemicals in the flask
• The gas escapes, so the weight goes down
• You can measure the weight lost.

When oil is extracted from the group, it is in the form of crude oil which is very thick, black liquid. No use for cars, lorries etc.

Oil is a hydrocarbon which means it is a compound containing hydrogen and carbon.

Most of the hydrocarbons in crude oil are called alkanes. There are many different alkanes but they all have similar properties.

The general formula for an ALKANE is Cn H 2n+2 

Methane 1 C H4

Ethane 2 C2 H6

Propane 3 C3 H8

Butane 4 C4 H10

The different hydrocarbons found in crude oil can be separated into fuels and other useful products. 

Method

• The crude oil is heated strongly
• Different alkanes in the crude oil have different boiling points because molecules are different sizes.
• The alkanes with lower boiling points evaporate at a lower temperature.
• As the temperature increases different alkanes with higher boiling points evaporate.
• In this way the crude oil can be separated into its different components called FRACTIONS 

• In an oil refinery the crude oil is heated very strongly until it boils. 
• The oil vapour is a mixture of many different size molecules (fractions)
• As the vapour mixture rises up through the fractionating column it gradually cools down.
• As it cools the larger molecules (higher boiling point fractions) condense and the liquid is removed from the column
• In this way the various fractions are separated from each other.

Hydrocarbon + Oxygen = Water + Carbon Dioxide

(Cobolt Chloride paper changes colour to pink to show gases contained water)

(Lime water went cloudy which shows the cases also contained CO2)

• This reaction is common to any hydrocarbon fuel. When the hydrocarbon burns the products are always CO2 and H20.
• This reaction is always Exothermic

We burn huge amounts of Hydrocarbons, this means we release huge amounts of CO2 into the atmosphere.

Our atmosphere is a mixture of different gases. The main constituents are: 

Nitrogen N2 78%

Oxygen  O2 21%

Argon (Inert Gas) Ar 0.9%

Water Vapour H2O 0.1% (Less Than)

Carbon Dioxide CO2 0.1% (Less Than)

Other Inert Gases He, Kr, Ne,Xe 0.1% (Less Than)

Inert means very unreactive (Group 0 so full outer shell) 

• The early atmosphere contained mostly water vapour, carbon dioxide with smaller amounts of ammonia, carbon monoxide, methane and nitrogen. Originally there was no oxygen.
• It was produced from volcanoes. Any hidrogen and helium in the atmosphere rapidly escaped into space because these light fast moving molecles escaped from the Earth's gravity.
• We know there was no oxygen in the early atmosphere because very old rock contain no oxygen.
• As the Earth cooled down the water vapour condensed. Carbon dioxide is soluble in water, so most of this gas dissolved in the newly formed oceans. 
• Fossil evidence shows the first living things called cyanobacteria developed about 3 billion years ago in the oceans. These used energy from the sun to convert CO2 into O2 in a process called photosynthesis.
• Much of the carbon dioxide dissolved in the oceans was converted into rock (chalk) by tiny sea creatures.
• As more simple plants developed the amount o CO2 in the atmosphere reduced and the amount of O2 increased.
• Some of the 02 formed a gas called ozone in the upper atmosphere. This is important because it shields the Earth from harmful U-V rays. Because of this protection, simple animal life could develop.
• Eventually the level of oxygen became high enough for simple animals to develop. They used up O2 and produced CO2 in a process called respiration.

Evenutally the various different processes stabilised and the atmosphre reached its modern composition. 

• Photosynthesis converting CO2 into O2 
• Respiration converting O2 into CO2

Over the last few centuries humans have burnt ever greater amounts of Fossil Fuels.

When these burn, they produce Carbon Dioxide, so the level of the gas in the atmosphere has begun to increase.

At the same time, we have cut down huge areas of vegetations, the the amount of Carbon Dioxide used up by plants in photosynthesis has reduced.

Sun to Earth- Solar radiation passes through the clear atmosphere

Earth - Most raidation is absorbed by the Earth's surface and warms it.

Earth To Space - Some solar radiation is reflected by the Earth and the atmosphere.

(Earth to Ozone Layer - infrared radiation is emitted from the Earth's surface

    - Some of the infrared radiation passes through the atmosphere and some is               absorbed and re-emitted in all directions by greenhouse gas molecules. The effect       of this is to warm the Earth's surface and the lower atmosphere)

Higher levels of Greenhouse gases in the atmosphere (mostly CO2) mean that less heat escapes from the Earth so the temperature gradually increases.