Chemical Changes

1) What is the pH Scale ?
The "p" stands for power or potential and the "H" stands for Hydrogen.
The pH scale measures the concentration of hydrogen ions in a solution.
Although the scale measures the concentration, it is actually inverted.
More hydrogen ions = more acidic = lower pH number
Less hydrogen ions = more alkali = higher pH number

2) How is the pH Scale connected to Water ?
Without water, there is no pH scale.
The entire scale is based on the unique properties of pure water.
Water is so chemically active that it constantly breaks itself apart.
In pure water, a tiny fraction of the water molecules naturally split apart (dissociate) into two types of ions:
In pure water, the number of Hydrogen ions = the number of Hydroxide ions = Neutral (pH 7).
Hydrogen ions = acidic
Hydroxide ions = alkaline

H_{2} O = H^{+} + O H^{-}

3) What happens when you dissolve Acids and Alkalis in Water ?
When you add an acid or an alkali to water, you upset the balance of these ions:
Acid - a substance that releases Hydrogen ions when dissolved in water to make a solution with PH<7
Alkali - a substance that releases Hydroxide ions when dissolved in water to make a solution with a PH>7

4) What is the range of the scale used to measure how Acid or Alkaline a substance is ?
The PH scale ranges from 0 to 14.
Substances with a PH less than 7 are called acids.
Substances with a PH more than 7 are called alkaline.

5) How can you measure the PH of a solution ?
pH Meter - A digital instrument with a glass probe that you dip into the liquid.
Indicator Strips / Litmus Paper - Small paper strips treated with chemical dyes that change color when dipped in liquid.
Liquid Indicator Solutions - You add a few drops of a liquid chemical directly into your solution.

6) What are the two most important elements in the periodic table ?
Hydrogen and Oxygen are the most important elements for life and our planet.
Oxygen is a diatomic element, meaning oxygen atoms always travel in pairs bonded together as a molecule

7) What is a SALT ?
This is the name of a substance made in a neutralisation reaction.
Do not confuse this with Table Salt (NaCl = sodium chloride)
"SALTS" is a broad family name for any ionic compound made from positive and negative ions.
Sodium chloride is just one type of salt. Not all salts contain sodium chloride.

8) What is Table Salt ?
Table salt is 97% to 99.9% pure sodium chloride (NaCl)

9) What is the difference between Table Salt and Sea Salt ?
Sea salt has tiny amounts of extra minerals like magnesium and potassium.
Table salt is heavily processed, mixed with anti-caking agents, and fortified with iodine.

10) What is the difference between Table Salt and Epson Salt ?
These are completely different chemical compounds with different molecular structures, tastes, and uses.
Table salt is sodium chloride (NaCl)
Epsom salt is magnesium sulfate (MgSO4 7H2O)

11) Can you give a list of the different types of SALTS ?
One way of organising the SALTS is by the name of the acid used.
Chloride Salts - Potassium chloride
Sulfate Salts - Copper sulfate, Calcium sulfate
Nitrate Salts - Potassium nitrate, Silver nitrate
Carbonate Salts - Calcium carbonate, Sodium bicarbonate

12) Which SALTS are soluble and which are insoluble ?
Soluble Salts
All Nitrates: Every single nitrate salt dissolves perfectly.
All Common Sodium, Potassium, and Ammonium Salts: These are always soluble.
Most Chlorides: Except for Silver Chloride and Lead Chloride
Most Sulfates: Except for Lead Sulfate, Barium Sulfate and Calcium Sulfate.
Insoluble Salts
Most Carbonates: Except for Sodium, Potassium, and Ammonium Carbonates.
Most Hydroxides: Except for Sodium, Potassium, and Ammonium Hydroxides (calcium hydroxide is slightly soluble).

13) What is a BASE ?
A base is any substance that will react with an acid to form a SALT.
Bases can be both soluble and insoluble in water.

14) Which BASES are soluble and which are insoluble ?
Soluble Bases
A small number of bases dissolve perfectly in water to form clear solutions.
Soluble bases are given a special chemical name: alkalis. All alkalis are bases, but not all bases are alkalis.
When they dissolve, they release free-moving hydroxide ions into the water, raising the pH above 7.
Sodium hydroxide, Potassium hydroxide and Calcium hydroxide.
Insoluble Bases
The vast majority of bases do not dissolve in water. When you mix them into a liquid, they remain as a solid powder at the bottom.
Even though they don't dissolve, they will still completely react with and neutralise an acid if you stir them into the solution.
Copper(II) oxide, Iron(III) oxide and Copper(II) carbonate.

15) What is a Strong Acid ?
These ionise completely in water.
These have a lower pH.
All the acid particles dissolve to release H+ ions

H C l = H^{+} + C l^{-}

Hydrochloric Acid = Hydrogen + Chloride

Sulfuric Acid = ? + ?

Nitric Acid = ? + ?

16) What is a Weak Acid ?
These do not ionise fully in the solution
These have a higher pH.
Only a small proportion of acid particles dissociate to release H= ions

C H_{3} C O O H = H^{+} + C H_{3} C O O^{-}

Ethanoic Acid = Hydrogen + Ethanoate

Carbonic Acid = ? + ?

Citric Acid = ? + ?

17) What is a Metal Oxide ?
All metal oxides are BASEs.
When a metal chemically reacts with oxygen.
This process is called oxidation = gaining oxygen, losing electrons.

2 M g + O_{2} = 2 M g O

Magnesium(s) + Oxygen(g) = Magnesium Oxide(s) 
Mg(2,8,2) + O(2,6) = Mg(2,8) + O(2,8)

4 F e + 3 O_{2} = 2 F e_{2} O_{3}

Iron(III)(s) + Oxygen(g) = Iron (III) Oxide(s)

2 C u + O_{2} = 2 C u O

Copper(s) + Oxygen(g) = Copper Oxide(s)

4 A l + 3 O_{2} = 2 A l_{2} O_{3}

Aluminium(s) + Oxygen(g) = Aluminium Oxide(s)

4 K + O_{2} = 2 K_{2} O

Potassium(s) + Oxygen(g) = Potassium Oxide(s)

O_{2} + 4 N a = 2 N a_{2} O

Sodium(s) + Oxygen(g) = Sodium Oxide(s)

18) What is it called when oxygen is removed from an Oxide ?
The reverse of this is called reduction = losing oxygen, gaining electrons.

P b O_{2} + C = P b + C O_{2}

Lead(IV) Oxide(s) + Carbon(s) = Lead(s) + Carbon Dioxide(g)

F e_{2} O_{3} (s) + 3 C O (g) = 2 F e (s) + 3 C O_{2} (g)

Iron(III) Oxide(s) + Carbon Monoxide(g) = Iron(s) + Carbon Dioxide(g)

19) What is a Metal Hydroxide ?
All metal hydroxides are BASEs.
When a metal chemically reacts to one or more hydroxide ions.
A metal hydroxide is an ionic compound containing a positive metal ion bonded to negative hydroxide ions
They are usually formed when a metal oxide dissolves in water or reacts with a water molecule.

2 N a + 2 H_{2} O = 2 N a O H + H_{2}

Sodium(s) + Water(l) = Sodium Hydroxide(aq) + Hydrogen(g)

C a + 2 H_{2} O = C a (O H)_{2} + H_{2}

Calcium(s) + Water(l) = Calcium Hydroxide(aq) + Hydrogen(g)

M g + 2 H_{2} O = M g (O H)_{2} + H_{2}

Magnesium(s) + Water(l) = Magnesium Hydroxide(s) + Hydrogen(g)

2 A l + 6 H_{2} O = 2 A l (O H)_{3} + 3 H_{2}

Aluminium(s) + Water(l) = Aluminum Hydroxide(s) + Hydrogen(g)

2 K + 2 H_{2} O = 2 K O H + H_{2}

Potassium(s) + Water(l) =  Potassium Hydroxide(s) + Hydrogen(g)

20) What is a Carbonate ?
A carbonate is a SALT of carbonic acid,
Carbonates are compounds containing CO32 ions.
Carbonates react with dilute acids to form a salt, carbon dioxide, and water.
example - calcium carbonate + hydrochloric acid = calcium chloride + carbon dioxide + water
example - copper2 carbonate = copper2 oxide + carbon dioxide

21) What are Metal Carbonates ?
All metal carbonates are BASEs.
When a metal chemically reacts to a carbonate ion.
Calcium Carbonate
Copper Carbonate
Magnesium Carbonate
Zinc Carbonate

22) What is a REDOX Reaction ?
REDuction and OXidation always happen at the same time.
If electrons are transferred, its a redox reaction.

23) How many different types of Chemical Reactions are there that involve hydrogen and oxygen ?
Combination (REDOX)
Displacement (REDOX)
Neutralisation
Combustion (REDOX)
Thermal Decomposition (REDOX)
Precipitation

24) What can these chemical reactions be used for ?
Generating Electricity
Medical Uses
Food Production and Cooking
Manufacturing and Industry
Heavy Duty Cleaning

25) Can you name the four factors that affect the rate of reaction ?
Temperature
Surface Area
Concentration / Pressure
Any Catalysts

26) What is a Combination Reaction ?
Also called a synthesis reaction.
This is when two seperate elements combine to form a single product.

2 N a + C l_{2} = 2 N a C l

Sodium + Chlorine = Sodium Chloride

2 N a + H_{2} = 2 N a H

Sodium + Hydrogen = Sodium Hydride

2 H_{2} + O_{2} = 2 H_{2} O

Hydrogen(g) + Oxygen(g) = Water(l)

2 H_{2} + C = C H_{4}

Hydrogen(g) + Carbon = Methane(g)

27) What is a Displacement Reaction ?
When a metal or the element Carbon (C) comes into contact with a metal in a compound that is lower in the reactivity series there will be a reaction.
A more reactive metal displaces a less reactive metal.
A more reactive metal forms stronger bonds with non-metals.

28) How many different types of Displacement Reactions are there ?
Metal-Metal Displacement

M g + C u S O_{4} = C u + M g S O_{4}

Magnesium(s) + Copper Sulfate(aq) = Copper + Magnesium Sulfate(aq)

4 N a + T i C l_{4} = 4 N a C l + T i

Sodium + Titanium Chloride = Sodium Chloride + Titanium

2 A l + 3 C u C l_{2} = 2 A l C l_{3} + 3 C u

Aluminium + Copper Chloride = Aluminium Chloride + Copper

F e + C u S O_{4} = F e S O_{4} + C u

Iron + Copper Sulfate = Iron Sulfate + Copper

Z n + C u S O = Z n S O_{4} + C u

Zinc + Copper Sulfate = Zinc Sulfate + Copper

3 C + 2 F e_{2} O_{3} = 3 C O_{2} + 4 F e

Carbon(s) + Iron(III) Oxide(s) = Carbon Dioxide(g) + Iron(s)

C + 2 C u O = 2 C u + C O_{2}

Carbon + Copper(II) Oxide = Copper + Carbon Dioxide 
This is the chemical equation for the extraction of copper from copper oxide using carbon 
where Cu = (Cu2 + 2e- = Cu)

C + 2 Z n O = 2 Z n + C O_{2}

Carbon + Zinc Oxide = Zinc + Carbon Monoxide

Halogen (Non-Metal) Displacement

C l_{2} + 2 K B r = 2 K C l + B r_{2}

Chlorine + Potassium Bromide = Potassium Chloride + Bromine

Metal-Acid (Hydrogen) Displacement

H_{2} S O_{4} + Z n = Z n S O_{4} + H_{2}

Sulfuric Acid + Zinc = Zinc Sulfate + Hydrogen

H_{2} S O_{4} + F e = F e S O_{4} + H_{2}

Sulfuric Acid + Iron = Iron(2) Sulfate + Hydrogen

2 H C l + Z n = Z n C l_{2} + H_{2}

Hydrochloric Acid + Zinc = Zinc Chloride + Hydrogen

2 H C l + 2 N a = 2 N a C l + H_{2}

Hydrochloric Acid + Sodium = Sodium Chloride + Hydrogen

2 H C l + M g = M g C l_{2} + H_{2}

Hydrochloric Acid + Magnesium = Magnesium Chloride + Hydrogen

29) What is a Neutralisation Reaction ?
When an acid and a BASE are mixed together, they react and the solution is neutral (pH 7).
acid + BASE (metal oxide) = SALT + water
acid + BASE (metal hydroxide) = SALT + water
acid + BASE (metal carbonate) = SALT + water + carbon dioxide
??
Metal Oxide

2 H C l + C u O = C u C l_{2} + H_{2} O

Hydrochloric Acid(aq) + Copper Oxide(s) = Copper Chloride(aq) + Water(l)

Metal Hydroxide

H C + N a O H = N a C l + H_{2} O

Hydrochloric Acid(aq) + Sodium Hydroxide(aq) = Sodium Chloride(aq) + Water(l)

H N O_{3} + K O H = K N O_{3} + H_{2} O

Nitric Acid(aq) + Potassium Hydroxide(aq) = Potassium Nitrate(aq) + Water(l)

2 H N O_{3} + C u (O H)_{2} = C u (N O_{3})_{2} + 2 H_{2} O

Nitric Acid(aq) + Copper Hydroxide(s) = Copper Nitrate(aq) + Water(l)

Metal Carbonate

H_{2} S O_{4} + C u C O_{3} = C u S O_{4} + H_{2} O + C O_{2}

Sulfuric Acid(aq) + Copper(II) Carbonate(s) = Copper(II) Sulfate(aq) + Water(l) + Carbon Dioxide(g)

30) What is a Combustion Reaction ?
A combustion reaction is a specific, fast type of oxidation known as burning, which always produces a noticeable amount of heat and light.

C_{25} H_{52} + 38 O_{2} = 25 C O_{2} + 26 H_{2} O

Wax(s) + Oxygen(g) = Carbon Dioxide(g) + Water(g)

31) What is a Thermal Decomposition Reaction ?
When a substance is heated and breaks down

C a C O_{3} = C a O + C O_{2}

Calcium Carbonate(s) + Heat = Calcium Oxide(s) + Carbon Dioxide(g)

32) What is a Precipitation Reaction ?

33) What is the Reactivity Series of metals ?
The more reactive a metal is, the more vigorous the reactions with acid and water are, and the more the temperature increases.
Potassium (K) - most reactive
Sodium (Na)
Lithium (Li)
Calcium (Ca)
Magnesium (Mg)
Aluminimum (Al)
Carbon (C) (GAS)
Zinc (Zn)
Iron (Fe)
Tin (Sn)
Lead (Pb)
Hydrogen (H) (GAS)
Copper (Cu)
Silver (Ag)
Gold (Au)
Platinum (Pt) - least reactive

34) What is the Reactivity Series of non-metals ?
Fluorine (F) - most reactive - Gas at room temperature this is a toxic, pale yellow gas.
Chlorine (Cl) - Gas at room temperature this is a toxic, pale green/yellow-green gas.
Bromine (Br) - Liquid - red brown
Iodine (I) - least reactive - Solid - Grey/dark grey

35) How can metals be extracted ?
Reduction
Displacement
Electrolysis (below)
Photomining
Bioleaching

36) Why do metals conduct electricity ?
Delocalised electrons can move freely and carry charge

37) What are Reacting Volumes ?
This refers to the exact amounts of gases or solutions that react together completely according to a balanced chemical equation.

38) What is the Haber Process ?
It produces Ammonia from Nitrogen and Hydrogen

39) What is Electrolysis ?
At the negative electrode positively charged ions gain electrons.

40) What is an Exothermic Reaction ?
This is a chemical reaction that transfers energy to the surroundings
rusting, camp fires, water evaporation, water + acid reacting, nuclear fusion

41) What is an Endothermic Reaction ?
This is a chemical reaction that takes energy from the surroundings
water to ice, cooking an egg, photosynthesis, dissolving salt in water, baking bread

42) What is an Enzyme ?
This is a biological catalyst

Metal Displacement with Silver Nitrate is a redox reaction
where the more reactive metal reacts with the silver nitrate causing
the solid metal to lose electrons (oxidize) plus oxygen
and the silver ions gain electrons (reduce) minus oxygen

Questions

43) What is an Ore ?
A natural rock containing valuable minerals with metals and metal compounds.

44) Are all substances either Acid, Alkali or Neutral ?
Yes, when dissolved in water, all aqueous solutions are classified as acidic, alkaline (basic), or neutral on the pH scale.
However, this only applies to solutions or substances that can interact with water.
Many solid materials and pure chemical compounds do not fit neatly into these categories until they are placed in a liquid solvent.

45) What happens when you mix an acid with an alkali ?
Hydrogen ions from the acid react with the hydroxide ions from the alkali to make water.

46) Do all Acids contain Hydrogen ions ?
No. A hydrogen ion is a proton

47) Do all Alkalis contain Hydroxide ions ?
No, but they all produce Hydroxide Ions when dissolved in water.
The most common alkalis are metal hydroxides
Amonia (NH3) is an alkali that does not have hydroxide in its formula.

48) What name is given to BASEs that dissolve in water ?
Alkalis

49) Is Water an Alkali ?
Pure water is neutral

50) What is Wax ?

51) What are Alkanes ?
general formula is CnH2n + 2

52) What is limewater ?

53) Define the term Hydrocarbon ?

54) What would you observe if Sodium and Potassium are reacted with water ?

55) Explain how crude oil is seperated into fractions ?

56) Will an insoluable BASE react with an acid ?
Yes. All bases react with an acid.

57) Can all the different types of metals be found in the ground ?
False.

58) How can solid salt be obtained from a salt solution ?
By Crystallation of the salt solution.

59) What is the chemical equation for the oxidation of iron ?

F e + C u S O_{4} = F e S O_{4} + C u

60) What is the rock salt experiment / seperation
(use warm water)

61) In the reactivity series which elements react with water ?
Potassium, Sodium, Lithium + Water
observations - float, fizzes, moves around, hydrogen produced
Calcium + Water
observations - fizzes, hydrogen produced, cloudy solution forms
Magnesium + Water
observations - bit of bubbling
(metals below Magnesium do not react)

62) What is the colour of these when dissolved in water ?
Fluorine (F) -
Chlorine (Cl) - pale green
Bromine (Br) - orange/yellow
Iodine (I) - brown

63) In the reactivity series which elements react with dilute acid (hydrochloric acid / sulfuric acid) ?
Potassium, Sodium, Lithium, Calcium, Magnesium
observation - lots of fizzing, fast reaction, hydrogen produced
Aluminium, Zinc, Iron, Tin, Lead
observation - some fizzing, gradual dissolving
Copper, Silver, Gold, Platinum
observation - no visible change

64) How does the atomic radius of atoms change throughout the periodic table and why ?
Atomic radius increase going DOWN - as there are more overall no of electrons
Atomic radius decreases going ACROSS - the increase of effective nuclear charge pulls electrons closer

65) How does the ionization energy change throughout the periodic table and why ?
Ionization energy increases going ACROSS - stronger nuclear attraction to harder to remove
Ionization energy decreases going DOWN - there is now an increase of the atomic radius and more inner shells making it easier to lose electrons