The kinetic theory of matter:
• All matter is made up of tiny, moving particles invisible to the naked eye.
• The particles move all the time. The higher the temperature the faster they move.
• Heavier particles move more slowly than lighter ones at a given temperature.
Sublimation: the rapid spreading out of the particles is called sublimation.
Intimate mixing: this occurs in liquid & gases because they do not diffuse fully.
Brownian motion: the random motion of particles caused by much smaller, invisible ones is called Brownian motion.
Charles law: when the temperature of a gas increased the volume also increased at constant pressure. V is directly proportional to T.
Boyle’s law: when the pressure was increased the volume of the gas was reduced. V is inversely proportional to T.
Combining the gas law: pV/T = constant
P1V1/T1 = P2V2/T2
Elements: any substance that cannot be broken down further, into a simpler substance.
Molecules: the atom of some elements are joined together in small groups. When an element exists as separate atoms then the molecules are said to be monatomic. The atoms of the hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine and iodine are each joined in pairs, they are known as diatomic molecules.
Compounds: are pure substances which are formed when two or more elements chemically combine together. Water is formed from the elements oxygen and hydrogen.
Oxidation: is addition of oxygen.
Reduction: is removal of oxygen.
Law of constant composition: compounds are made up of fixed proportions of elements, the have a fixed composition.
Filtration: it is a technique used when solid needs to be separated from a liquid. Sand can be separated from a mixture of water by filtering through filter paper. Sand is residue and water is the filtrate.
Composite materials: are those that combine the properties of two constituents in order to get the exact properties needed for a particular job.
Centrifuging: separation of mixture by rapid spinning. The denser particles are flung to the bottom of the containing tubes. The liquid can then be decanted off.
Group1- alkali metals:
• They are good conductor of electricity and heat.
• They are often soft metals.
• They are metals with low densities.
• They have shiny surfaces when freshly cut with knife.
• They have low melting points.
• They burn in oxygen or air with characteristic flame colours to form white solid oxides.
• They reacts vigorously with water to give an alkaline solution of the metals hydroxide as well as producing hydrogen gas.
• They react vigorously with halogens to forms metal halides.
Group2-alkaline earth metals:
• They are harder than those in group1.
• They are silvery grey in color when pure & clean.
• They are good conductor of heat and electricity.
• The burn in air/oxygen with characteristic flame colors to form solid white oxides.
• They react with water but they do so much less vigorously than the elements in group1.
Groups7-halogens:
• These elements are colored and darken down the down group.
• They exist as diatomic molecules.
• They show a gradual change from a gas through a liquid to a solid.
• They form molecular compounds with other non-metallic elements.
• They react with hydrogen to produce the hydrogen halides, which dissolve in water to form acidic solutions.
• They react with metals to produce ionic metal halides.
Group0-noble gases:
• They are colorless gases.
• They exist as individual atoms, He, Ne and Ar.
• They are very reactive.
Transition elements:
• They are harder and stronger than metals in groups 1 & 2.
• They have much higher densities than metals in groups 1 and 2.
• They have high melting.
• They are less reactive metals.
• They form a range of brightly colored compounds.
• They are good conductor of heat and electricity.
• They do not react so quickly with air or water.
• They form simple ions with more than one oxidation state.
• They show catalytic activity as elements and compounds.
Ionic bonding: ionic bonding is usually found in compounds that contain metals combined with non-metals. In this type electrons are transferred from the meta atom to the non-metal atoms during the chemical reaction.
Properties of ionic compounds:
• They are usually solid at room temperature with high melting points.
• They are usually hard substances.
• They usually cannot conduct electricity because the ions are not free to move.
• They mainly dissolve in water.
• They usually conduct electricity when in the molten state or aqueous solution.
Covalent bonding: this occurs in b/w non-metals atoms, and the bond formed is called covalent bond.
Double covalent bond: in which two pair of electrons are shared in each case.
giant molecular or macromolecular: are structures containing many hundred of thousands of atoms joined by strong covalent bond. Such as diamond, graphite and silicon (IV) oxide.
Properties of covalent bond:
• As simple molecular substances, they are usually gases, liquids or solids with low melting and boiling points.
• They do not conduct electricity when molten or dissolves in water, because they do not contain ions.
• They do not dissolve in water.
Allotropy: when elements can exists in more than one physical form in the same state. Such as sulphur, tin and carbon.
Allotropy of carbon: carbon is a non-metallic element which exists in more than one solid structural form, such as diamond and graphite.
Graphite: each layer each carbon atom is bonded to three others by strong covalent bonds.
Diamond: each of the carbon atoms in the giant structure is covalently bonded to four others.
Properties of metal:
• They usually have high melting and boiling points due to strong attraction b/w the positive metal ions.
• They conduct electricity due to the mobile electron within the metals structure.
• They are malleable and ductile.
• They have high densities because the atoms are very closely packed in a regular manner.
Lattice: a regular three dimensional arrangements of atom/ions in a crystalline solid.
Electrolysis: is a process of splitting up substances by passing an electric current through them. The substance which decomposes is called the electrolyte.
• Substances which do not conduct electricity when in molten state or in solution are called non electrolytes.
• Substances which conduct electricity to a small extent in the molten state or in solution are called weak electrolytes.
Electrolysis of aluminium oxide: bauxite an impure form of aluminium oxide is first treated with sodium hydroxide to obtain pure aluminium oxide, removing impurities such as iron (III) oxide and sand. This improves the conductivity of the molten aluminium oxide. This aluminium is then dissolved in molten cryolite. Cryolite a mineral is used to reduce the working temperature of the Hall-Heroult cell from 2017 degree to between 800 to 1000 degree. This molten mixture is then electrolysed in a cell. The anode of this process is blocks of graphite. The cathode is the graphite lining of the steel vessel containing the cell. When aluminium is melted the ions become mobile, as the strong electrostatic force of attraction between them are broken by the input of heat energy.
Anodizing: this is a process in which the surface coating of aluminium is made thicker.
Extraction of sodium: sodium chloride is mixed with calcium chloride and melted. The calcium chloride is added to sodium chloride electrolyte to reduce the working temperature of the cell from 801 degree to 600 degree. The mixture is then electrolysed in a cell. The chloride is a circle of steel around the graphite anode. At 600 degree sodium and chlorine would react violently together to re-form sodium chloride. The molten sodium floats on the electrolyte and is run off for storage. Sodium is used as a liquid coolant in the nuclear power stations as well as in street lighting and in the production of metals such as titanium.
Electrolysis of water: to make water to conduct electricity some sulphuric acid is added. The power is turned on and electric current flows through this solution, gases are seen at the two electrodes. The gas collect at the cathode burns with a squeaky pop, showing to be hydrogen.
