Chemistry

• Reduction -a chemical reaction in which a substance loses oxygen &/or gains electrons
• Soluble -a substance which is able to dissolve in water
• Acid-Solution of pH less than 7
• Displacement-a chemical reaction in which a more reactive element reacts with a compound and takes the place of a less reactive element in that compound
• Insoluble -a substance which is unable to dissolve in water
• Reactivity-the tendency of a substance to undergo chemical reaction
• Ores-are naturally occuring rocks that contain metal or metal compounds in sufficient amounts to make it worthwhile extracting them
• Neutralisation-a chemical reaction in which an acid and base react to form salt &water
• Base-a substance which will react with acids
• Oxidation -a chemical reaction in which a substance gains oxygen &/prloses electrons
• Metal oxide -a compound containing only a metal & oxygen
• Salt-the substance formed when an acid reacts with a base
• Metals come from the earths crust.some metals, like gold are very unreactive & are found as elements in their native state.metals such as zinc,lead&iron are found combined with oxygen in compounds.these metals can be extracted using chemical reactions.the metal oxides are reduced as oxygen is removed from the compound
• Redox reactions like displacement reactions can be represented by 2 half equations
• Electrolysis-breaking down a compound using electricity
• Electrolyte -substance that is having current passed through it.either an aqueous solution or molten ionic compound
• Anode-negative ions lose electrons

  Cathode- positive ions gain electrons

  
• Positive

  Anode

  Negative

  Is

  Cathode
• Oxidation

  Is

  Loss

  Reduction

  Is

  Gain
• Lead bromide is unusual as it has a low melting point for ionic substances
• All metals can be extracted by electrolysis however large amounts of energy are used in the extraction process to melt the compounds &it is a waste of time
• Half equations

  
• Rules to learn(aqueous solution)

  At the Cathode

  -if the metal ion is lower than hydrogen in the reactivity series the metal is formed

  -if the metal is higher than hydrogen in the reactivity series, hydrogen is formed

  At the anode

  -if the ion is a halide ion then this ion is discharged forming it's element

  -if the ion is a complex ion then the hydroxide ion is discharged forming oxygen
• Ph scale -universal indicator tells us if a solution is acidic or alkaline.It also tells you if a solution is a strong or weak acid or alkaline

  
• Acids are substances that produce hydrogen ions in solution

  Alkaline are substances that produce hydroxide ions In solution
• Strong acids ionise completely when dissolved in water.strong acids therefore have a high concentration of h+ ions & low ph
• Weak acid only partially ionise in water therefore have low concentration of H+ ions & higher ph
• General equation:metal+acid -salt +hydrogen
• Salts have 2 parts to their name

  First from metal second from acid
• H,O,F,Br,I,N,CL-symbols for diatomic elements
• Acids are neutralized By alkali &bases to produce salts&water

  (acid + base - salt +water)
• As with reactions of metals with acids, the salt produced is dependent upon the positive ions in the base & acid used
• Acids can Be neutralized By metal carbonates to produce salts&water but also carbon dioxide gases
• Cryolite is added to aluminum to lower melting point
• When chemicals react atoms are not made or destroyed they are rearranged as a result the total mass is always conserved during a chemical reaction
• Train track method

  1.write a pair of lines below the arrow,write the symbols of elements in between the lines

  2write down how many of each element is on each side

  3.if elements don't balance you must add a multiplier in front of the substance.do this 1 at a time account for each change in atoms
• Avagadros number -the weight of units in one mole of any substance equal to 6.02×10²³
• Relative atomic mass-the mass of an atom of an element relative to carbon 12 .this will equal the number of protons& neutron's in the element
• Solvent-the liquid in which a solute is dissolved
• Products -the substances that are produced in a chemical reaction