Topic 4 - Elements

Question 1

Define element

Answer 1

A substance containing only one type of atom

Question 2

Describe metals

Answer 2

• shiny
• malleable, ductile
• conduct electricity and heat well
• high melting points
• high density
• hard

Question 3

Describe non-metals

Answer 3

• dull appearance
• not malleable or ductile
• conduct electricity and heat badly
• low melting point
• low density
• brittle

Question 4

Name the diatomic elements

Answer 4

Bromine
Oxygen
Chlorine
Iodine
Hydrogen
Astatine
Nitrogen
Fluorine

Question 5

Describe the percentages of gases in air

Answer 5

Nitrogen - 78%
Oxygen - 21%
Argon - 1%
Carbon dioxide - 0.04%

Question 6

Describe the phosphorus test for the percentage of oxygen in air

Answer 6

1) Fill a gas syringe will 100cm3 of air and pass it across heated phosphorus in the centre to an empty gas syringe
2) the oxygen in the air reacts with the phosphorus, so the volume left over is everything in the air excepting oxygen

Question 7

Describe the iron experiment to find the percentage of oxygen in air

Answer 7

1) soak some iron wool in acetic acid (to catalyse the reaction). Then push the wool into a measuring cylinder and invert the measuring cylinder into a beaker of water
2) record the starting position of the water using the scale on the measuring cylinder - this is the starting volume of air
3) over time, the level of the water in the measuring cylinder will rise
4) this is because the Ron reacts with the oxygen the air to make iron oxide- the water rises to fill the space which the water took up
5) leave the measuring cylinder for around a week or until the water level stops changing
6) record the finishing position of the water - this is the final volume of air
7) calculate percentage by subtracting the final volume from the initial volume, dividing by the start volume and multiplying by 100

Question 8

Describe the practical for the preparation of oxygen

Answer 8

Put H202 (hydrogen peroxide) in a conical flask with the catalyst MnO2 (manganese IV oxide) 
Bung the top of a conical flask and run a delivery tube from inside the conical flask to an upside down test tube that is underwater to collect the O2
Equation: 2H202 -> 2H20 + O2

Question 9

What is the test for oxygen

Answer 9

Glowing splint relights

Question 10

Describe the general formula for oxygen reacting with elements

Answer 10

Oxygen + element -> element oxide

Question 11

Describe the equation and observations of the reaction of magnesium and oxygen

Answer 11

Equation: 2Mg(s) + 02(g) -> MgO (s)
Observations: bright white flame, white powder formed (which is slightly alkaline when dissolved in water)

Question 12

Describe the equation and observations for the reaction between sulphur and and oxygen

Answer 12

Equation: S(s) + O2 (g) -> SO2 (g)
Observation: pale blue flame
Sulphur dioxide is acidic when dissolved in water

Question 13

Describe the equation and observations of the reaction between hydrogen and oxygen

Answer 13

2H2(g) + O2(g) -> 2H2O(g)
• burns very easily, can be explosive, squeaky pop
• orangey/yellow flame

Question 14

Describe metal oxides

Answer 14

They are basic

Question 15

Describe non-metal oxides

Answer 15

They are acidic

Question 16

What is the cause of acid rain?

Answer 16

Nitrogen oxides and sulphur dioxides released by fuel combustion

Question 17

Why is acid rain bad?

Answer 17

• makes water bodies acidic, killing aquatic life
• damages buildings, corrodes limestone
• damages waxy cuticles of trees, making it more difficult for them to absorb nutrients