Chemistry Chemical Changes

metal oxides

metal + oxygen -> metal oxides, the metal oxidises because it gains oxygen. reduction is the proses of a metal losing oxygen

reactivity series 1

when metals react with other substances it tends to turn into a positive ion, metals can be placed in a reactivity series: Metals potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper when reaction with water and dilute acids

reactivity series 2

potasium : violent

sodium : very quick

lithium : quick

calcium : more slow

these metals reacting with water

reactive series 3

calcium : very quick

magnesium : quick

zinc : fairly slow

iron : more slow

copper : slow

these metals reacting with dilute acids

reactive series 4

as you go up the list from copper to potasium the metals become more reactive

potasium to calcium = reaction with water

potasium to copper = reaction with dilute acids

extraction of metals

gold is unreactive so it can be found in the Earth however most metals are found as compouds with other substances which means we need to extract them via chemical reactions

oxidation and reduction in terms of electrons

OIL RIG : oxidation is loss reduction is gain (in terms of electrons)

reactions of acids with metals

acids which react with metals to form salts and hydrogen. This is a redox reaction where one of the substances are reduced and the other is oxidised = metals are reduce and the acids are oxidised. must remember OIL RIG

acid neutralisation

acids can be neutralised with alkili and bases to form salt water, they can also be neutralised using a metal carbonate to produce salt water and carbon dioxide. the type of salt produced depends of the alkili and base used, for example hydrochloric acid produces chloride, nitric acids produce nitrate and sulfuric acids produce sulferates. it could also depends on the positive charge of the base or alkili or carbonate

soluable salts

made from acids and reacting them with insoluable subtances:

1) add substance into the acid so it disolves

2) acid is neutralised when exess solid sinks to bottom

3) filter the exess material and evaporate some water, then let the remaining subtance evaporate slowly

(crystalysation)

pH scale

from 0 to 14. any number >7 is alkiline while and <7 is acidic. 7 is neutral. this scale is used to mesure the alkilinity or acidity of a substance

strong and weak acids

stronger acids are fully ionised in a aqueous substance and have a higher pH number

weaker acids are partially ionised and have a lower pH number

pH decreases by 1 and the concentration of H increases buy 10 (indirectley proportional)

strong and weak refers to the H concentration of ions in a aqueous solution whereas dilute and concentrated refers to the amount of the substance.

process of electrolysis

ionic substance is disolved in a liquid and its positive ions are free to move about. passing current through the solution means solution can be broken down into element. the solution being broken down = electrolyte

p ions move to negetive electrode (cathode) while n ions move to the p electrode (anode)

electrolysis of molten ionic compounds

ionic compound is electrolised down into molten state. the metal ions will be atracted to the cathode and the non-metal ions will move to the anode

using electrolysis to extract metals

large amounts of energy needed to electrolise the metals and create the current. aluminium is molten into aluminium oxide and cryolite using carbon as the anode

metals that react with carbon can be extracted with electrolysis

(cannot use carbon for extraction bc the metals are more reactive than it)

electrolysis of aqueous solution

• Cathode (−): Hydrogen gas (H₂) is produced unless the metal ion is less reactive than hydrogen; in that case, the metal is deposited.​

• Anode (+): If halide ions (Cl⁻, Br⁻, I⁻) are present, the corresponding halogen is released. If no halide is present, oxygen gas (O₂) is produced from hydroxide ions (OH⁻).​

• This occurs because water partially ionizes into H⁺ and OH⁻, and the discharge of ions depends on their relative reactivity.

hald equations

equations that show the oxidation and reduction processes during electrolysis.