Chemical Changes

Question 1

Describe how metals react with oxygen and state the compound they form, define oxidation and reduction

Answer 1

Metal + oxygen = metal oxide

Oxidation - addition of oxygen (loss of electron)

Reduction - removal of oxygen (gain of electrons)

Question 2

Describe the arrangement of metals in the reactivity series, including carbon and hydrogen, and use the reactivity series to predict the outcome of displacement reactions

Answer 2

Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper

Question 3

Recall and describe the reactions, if any, of potassium with water or dilute acids

Answer 3

Potassium + dilute acid = explosive reaction

Potassium + water = a reaction

Question 4

Recall and describe the reactions, if any, of sodium with water or dilute acids

Answer 4

Sodium + dilute acid = explosive reaction

Sodium + water = reaction

Question 5

Recall and describe the reactions, if any, of lithium with water or dilute acids

Answer 5

Lithium + dilute acid = explosive reaction

Lithium + water = reaction

Question 6

Recall and describe the reactions, if any, of calcium with water or dilute acids

Answer 6

Calcium + dilute acid = explosive reaction

Calcium + water = reaction

Question 7

Recall and describe the reactions, if any, of magnesium with water or dilute acids

Answer 7

Magnesium + dilute acid = moderate reaction

Magnesium + water = no reaction

Question 8

Recall and describe the reactions, if any, of zinc with water or dilute acids

Answer 8

Zinc + dilute acid = moderate reaction

Zinc + water = no reaction

Question 9

Recall and describe the reactions, if any, of iron with water or dilute acids

Answer 9

Iron + dilute acid = moderate reaction

Iron + water = no reaction

Question 10

Recall and describe the reactions, if any, of copper with water or dilute acids

Answer 10

Copper + dilute acid = no reaction

Copper + water = no reaction

Question 11

Relate the reactivity of metals to its tendency to form positive ions and be able to deduce an order of reactivity of metals based on experimental results

Answer 11

The more reactive metals form positive ions more easily, this also means they react with water and acid easily

Question 12

Recall what native metals are and explain how metals can be extracted from the compounds in which they are found in nature by reduction with carbon

Answer 12

Native metals - a pure metal in its metallic form in nature

Potassium, sodium, lithium, calcium and magnesium can be extracted from compounds using electrolysis.

Zinc, iron and copper can be extracted from their oxides using carbon.

Question 13

HT ONLY: Describe oxidation and reduction in terms of loss and gain of electrons

Answer 13

Oxidation - loss of electrons

Reduction - gain of electrons

Question 14

HT ONLY: Write ionic equations for displacement reactions, and identify which species are oxidised and reduced from a symbol or half equation

Answer 14

Mg(s) + Zn2+(aq) = Mg2+(aq) + Zn(s)

Oxidation - Mg = Mg2+ + 2e-

Reduction - Zn2+ + 2e- = Zn

Question 15

Explain that acids can be neutralised by alkalis, bases and metal carbonates and list the products of each of these reactions

Answer 15

H+ + 0H- = H₂0

Acid + alkali = water (neutral)

Acid + metal carbonate = salt + water + carbon dioxide

Acid + metal oxide = salt + water

Acid + metal hydroxide = salt + water

Question 16

Predict the salt produced in a neutralisation reaction based on the acid used and the positive ions in the base, alkali or carbonate and use the formulae of common ions to deduce the formulae of the salt

Answer 16

HCl - chloride

H2SO4 - sulfate

HNO3 - nitrate

Question 17

Describe how soluble salts can be made from acids and how pure, dry samples of salts can be obtained

Answer 17

Soluble salts are made from adding metals and insoluble metal compounds to acids. The excess solid is filtered and remaining salt solution if crystallised.

Question 18

Recall what the pH scale measures and describe the scale used to identify acidic, neutral or alkaline solutions

Answer 18

The pH scale measures what pH the substance is in terms of how acidic or alkaline it is or if it’s neutral.

Question 19

Define the terms acid and alkali in terms of production of hydrogen ions or hydroxide ions (in solution), define the term base

Answer 19

Acid - pH less than 7, produces H+ ions in water

Alkali - pH more than 7. produces OH- ions in water

Base - a substance with a pH higher than 7

Question 20

Describe the use of universal indicator to measure the approximate pH of a solution and use the pH scale to identify acidic or alkaline solutions

Answer 20

The universal indicator changes colour depending on the pH - it gives an approximate value. You can use the pH scale to use the colour the universal indicator provides to identify the exact pH.

Question 21

HT ONLY: Use and explain the terms dilute and concentrated (in terms of amount of substance) and weak and strong (in terms of the degree of ionisation) in relation to acids

Answer 21

Dilute - low concentration (low amount of particles)

Concentrate - high concentartion (high number of particles)

Weak acid - partially ionises in water to produce hydrogen ions.

Strong acid - completely ionises in water to produce hydrogen ions

Question 22

HT ONLY: Explain how the concentration of an aqueous solution and the strength of an acid affects the pH of the solution and how pH is related to the hydrogen ion concentration of a solution

Answer 22

The pH will be lower if there is a higher concentration.

Question 23

Describe how ionic compounds can conduct electricity when dissolved in water and describe these solutions as electrolytes

Answer 23

Ionic compounds can conduct electricity when in electrolytes due to the electrons being free to move and carry charge.

Question 24

Describe the process of electrolysis

Answer 24

Electrolysis - the process in which a ionic compound is broken down into its elements using a electrical current

Question 25

Use the reactivity series to explain why some metals are extracted with electrolysis instead of carbon

Answer 25

Some metals are extracted with electrolysis instead of carbon due to being more reactive than carbon.