Boiling happens when the liquid is heated so strongly that the particles move fast enough to break all the forces of attraction in the liquid, boiling it.
Apparatus - Have Gas Jar of Air on top of Gas jar of Bromine. If the lids are removed, the bromine diffuses upwards until both jars are brown.
Fractional Distillation is used to separate liquidssuch as alchohol and water - they are separated by their different boiling points.
To separate alchohol and water, control the temperature of the column so that all the water condenses in the column and trickles back into the flask, so that only the alchohol remains as a vapour all the way to the top.
Simple Molecular Structures
- Simple Molecular Compoounds tend to be gases, liquids or solids with a low melting point
- Molecular substances tend to be insoluble in water unless they react with it.
- Molecular substances are often soluble in organic solvents
- Molecular Substances DO NOT conduct electricity - the molecules do not have any overall electrical charge, and there are no electrons mobile enough to move from molecule to molecule
Giant Covalent Substances
- Diamond is a form of pure carbon. Each carbon atom has for unpaired electrons in its outer energy level and uses these to form four covalent bonds. Thnis forms a tetrahedral arrangement
- Diamond is very hard, with a very high melting and boiling point.
- It does not conduct electricity
- It does not dissolve in water or any oteher solvent.
- Graphite is a form of carbon, with a layer structure, similar to a pack of cards
- It is a soft material with a slimy feel
- It is used in pencils, and as a dry lubricant
- It has a high melting and boiling point.
- It is insoluble
- It is less dense than Diamond
- It conducts electricity
Compounds Conducting Electricity
Ionic Compounds only conduct electricity when in Molten or Solution
Covalent Compounds DO NOT conduct Electricity
Electrolytes are Liquids that Conduct Electricity. They are usually made by melting or dissolving ionic compounds.
When a conductivity probe is placed in an electrolyte, current flows through the circuit, so it is an electrolyte. If current does not flow, then the substance is not an electrolyte.
Alkali Metal + Water Reactions
Metal + Water --> Metal Hydroxide + Hydrogen
- Reactive Metals, such as Potassium, Lithium, Sodium and Calcium, all react vigorously with water.
- Less Reactive Metals (Magnesium, Zinc, Iron) will not react well with water, but will with steam
- Copper does not react with metal or steam
Boiling Point of Halogens
The boiling point of the halogens increases as you go down the group.
- Chlorine: -34*C
- Bromine: 59*C
- Iodine: 195*C
HCl + Water Reaction
Halogens react with Hydrogen to form hydrogen halides
When HCl is dissolved in water, it splits up into H+ ions and Cl- ions, forming Hydrochloric Acid.
HCl + MethylBenzene Reaction
If HCl is dissolved in an organic solvent such as Methylbenzene, it does not dissociate into H+ and Cl- ions. This means that there are no H+ ions produced, and it is not acidic.
- KCl + Bromine Water/Iodine Water --> No Reaction
- KBr + Iodine Water --> No Reaction
- KBr + Chlorine Water --> Orange Solution
- KI + Chlorine Water/Bromine Water --> Black Solution
Acid + Metal
Acid + Metal --> Salt + Hydrogen
The speed of the reaction is indicated by the rate that which the bubbles of hydrogen are given off.
Made from Hydrogen Peroxide.
The Hydrogen Peroxide decomposes into water and oxygen, and the oxygen is collected over water.
Magnesium - Gives White Flame, and forms white MgO powder
Carbon - Gives yellow flame, and forms carbon dioxide gas
Sulphur - Gives pale blue flame, and forms sulphur oxide
Carbon Dioxide Preparation
Calcium Carbonate chips are placed at the bottom of the test tube, and hydrochloric acid is added. The HCl reacts with the marble chips, and calcium chloride, water, and Carbon Dioxide Gas is produced. The Carbon Dioxide gas is collected in a gas syringe.
Uses of Carbon Dioxide
Carbon Dioxide is used in Fizzy Drinks and Fire Extinguishers, however it also is a greenhouse gas.
Tests for Carbonates
Test with HCl - If Carbonates are present, then Carbon Dioxide will be released
When a sample is pure, it will only be made up of one substance.
If water is pure, it will always boil at 100*C and freeze at 0*C. Therefore, if the sample does not boil at 100*C or freeze at 0*C, then it is impure.
Halogen + Alkane
Halogens react with Alkanes, in the presence of ultraviolet light, to make Haloalkanes. In these reactions, a hydrogen atom from the alkane is substituted for a chlorine or bromine atom. This is a substitution reaction.
Halogen + Alkene
Halogens react with Alkenes to make Haloalkanes. They are still Haloalkanes, as the double bond is split, and a halogen atom given to both Carbons. This is an addition reaction.
Litmus Paper and other Indicators
Litmus Paper = Red in Acidic, Purple in Neutral, Blue in Alkaline solutions.
Phenolphathein = Colourless in Acidic, Bright Pink in Alkaline solutions.
Methyl Orange = Red in Acidic, Yellow in Alkaline solutions.
Universal Indicator - shows colours in pH Scale
- Sodium, Potassium and Ammonium salts are SOLUBLE
- Nitrates are SOLUBLE
- Most Chlorides are SOLUBLE
- however Silver Chloride is INSOLUBLE
- Most Sulphates are SOLUBLE
- however Barium Sulphate and Calcium Sulphate are INSOLUBLE
- Most Carbonates are INSOLUBLE
- however Sodium,Potassium and Aluminium Carbonates are SOLUBLE
- Using a pipette, add some alkali to a conical flask, along with a few drops of Phenolphathein indicator
- Fill a burette with the acid
- Using the burette, add the acid to the alkali one bit at a time, and give the conical flask a regular swirl.
- The indicator changes colour when all the alkali has been neutralised.
- Record the volume of acid used to neutralise the alkali, and repeat a few times.
Rate of Reaction Measurements
- Measuring Precipitation - Observe a marker through a solution and measure how long it takes for it to disappear. The quicker it disappears, the quicker the reaction.
- Measuring Change in Mass - This can be carried out on a mass balance, when the reaction produces a gas. As the gas is released, the mass disappearing is measured on the balance. The quicker the reading on the balance drops, the faster the reaction.
- Measuring Volume of a gas given off - This needs a gas syringe to measure the volume of the gas given off. The more gas given off during a given time interval, the faster the reaction.
An Enthalpy Change is the total energy absorbed to break bonds - the total energy released in making bonds
Measuring enthalpy changes - Calorimetry - measures the amount of energy transferred in a chemical reaction
Shown by /\H - If exothermic, it is negative, if endothermic, it is positive.
The activation energy is the minimum amount of energy for the particles in a reaction to collide with each other.
Adding a Catalyst lowers the activation energy, meaning that reactions are quicker.
Role of Carbon in Metal Extraction
When a metal is less reactive than carbon, the metal is extracted by a reduction reaction with carbon, by heating the ore with CO.
When a metal is more reactive than carbon, the metal is extracted by electrolysis.
Electrolysis of Aluminium
- Aluminium is an abundant metal but is found naturally in compounds, the main ore of which being bauxide. A white powder of pure Aluminium Oxide is left after mining and purifying.
- Aluminium Oxide has a very high melting point of over 2000*C, so it is dissolved in Molten Cryolite, bringing the temperature down to 900*C.
- The electrodes are made of graphite.
- As molten aluminium oxide contains free ions, it conducts electricity.
- The positive aluminium ions are attracted to the cathode and turn into aluminium atoms.
- This is a redox reaction, as the negative oxide ions are attracted to the positive electrode (anode).
- Negative Electrode Equation = Al(3+) + 3e(-) --> Al
Iron Extraction in the Blast Furnace
Reducing Iron Ore to Iron
- Hot air is blasted intop the blast furnace, and the coke (carbon) burns faster than normal, raising the temperature to 1500*C
- The coke burns and produces Carbon Dioxide, which then reacts with unburnt coke to form CO.
- This reduces the iron ore to iron
- As the iron is molten at this temperature, and is very dense, it runs to the bottom of the furnace where it is tapped off.
- Limestone then removes the sand from the iron. It is decomposed by the heat into Calcium Oxide and Carbon Dioxide. The Calcium Oxide then reacts with the sand to form Slag.
Uses of Iron
- Wrough Iron is pure iron, it is malleable and i sused to make ornamental gates and railings
- It is also mixed with other elements to make alloys, to make more such as cooking pans, manhole covers, car bodies and girders
- Stainless Stell is an alloy made of iron and chromium that doesn't rust, and is used for cutlery and cooking pans.
Fractional Distillation - Crude Oil
- See Card 3 for Full Description of Frac. Dist.
- The crude oil is heated until most of it has turned into gas. The gases enter a fractionating column
- In the column, there is a temperature gradient. When the substances that make up crude oil reach a part of the column where the temperature is lower than their boiling point, they condense
- The longer hydrocarbons have lower boiling points, and turn to liquid and drain out later on
- Bubble caps in the fractionating column stop the separated liquids from running back down the column and remixing, ending up with the crude oil mixture separated into different fractions - Refinery Gases, Gasoline , Naphtha, Kerosene, Fuel Oil, Diesel and Bitumen.
Burning Fuels produces pollutants such as CO, Nitrogen Oxides and Sulphur Dioxide.
Sulphur Dioxides and Nitrogen Oxides come from Burning Fuel, and cause acid rain when they mix with clouds.
Carbon Monoxide is a poisonous gas formed by incomplete combustion. It stops blood cells carrying oxygen around the body, by combining with haemoglobin in blood cells.
Use of Polymers
Poly(ethene) is a light, stretchable polymer, making it useful for packaging.
Poly(propene) is a tough polymer, which is flexible and resistant to heat. It is used to make kettles, food containers and carpets
Poly(chloroethene) is used to make clothes and pipes and for insulating electrical cables.
Use of Ammonia
Ammonia is used in the Ostwald Process to make Nitric Acid, which is reacted with to make Ammonium Fertiliser. It is a very strong fertiliser as it has nitrogen in two different places, and therefore it is more effective than normal substances