SCIENCE CHEMISTRY (Sec3): Chpt1_Experimental Chemistry

Question 1

Mass (physical property) [4pts]

Answer 1

• how much matter is present in a substance
• SI unit: Kilogram (kg)
• other common units: gram (g), tonnes (t)
• measuring apparatus: beam balance, electronic balance (measures solid)

Question 2

Time (physical property) [4pts]

Answer 2

• how long it takes for something to happen, duration of an event
• SI unit: Second (s)
• other common units: minute (min), hour (h)
• measuring apparatus: mechanical (analogue) stopwatch, digital stopwatch, hourglass

Question 3

Temperature (physical property) [4pts]

Answer 3

• the measure of how hot or cold something is
• SI unit: kelvin (K)
• other common units: Degree Celsius (°C), Degree Fahrenheit (°F)
• measuring apparatus: alcohol-in-glass thermometer, mercury-in-glass thermometer, digital laboratory thermometer, oral digital thermometer

Question 4

Volume (physical property) [4pts]

Answer 4

• the amount of space something occupies
• SI unit: cubic metre (m^3)
• other common units:cm^3, ml, l
• measuring apparatus: beaker, gas syringe, measuring cylinder (liquid), burette (liquid), pipette (liquid), volumetric flask (liquid)

Question 5

conversion: time [2pts]

Answer 5

1min = 60s

1h = 60min = 3600s

Question 6

conversion: volume [1pt]

Answer 6

1m^3 = 1000dm^3 = 1 000 000cm^3

Question 6

conversion: temperature [1pt]

Answer 6

Temperature in K = Temperature in °C + 273

Question 7

pipette (meaning + examples)

Answer 7

accurate fixed volumes (e.g. 10.0cm^3 or 25.0cm^3)

Question 7

conversion: mass [3pts]

Answer 7

1kg = 1000g = 1 000 000mg

1 t = 1000kg = 1 000 000g

1 kt = 1000t = 1 000 000kg

Question 8

conversion: length [1pt]

Answer 8

1m = 10dm = 100cm = 1000mm

Question 9

volumetric flask (meaning + examples)

Answer 9

accurate fixed volumes that are larger (e.g. 100cm^3 or 250cm^3)

Question 10

measuring cylinder (meaning + examples)

Answer 10

a range of volumes to the nearest 0.5cm^3 (e.g. 31.5cm^3, 23.0cm^3)

Question 11

burette (meaning + examples)

Answer 11

a range of volumes to the nearest 0.05cm^3 (e.g. 31.55cm^3, 23.00cm^3)

Question 12

beaker (meaning)

Answer 12

measure volumes of liquids approximately according to graduated marks on apparatus

Question 13

gas syringe (meaning)

Answer 13

accurately measure volumes of gases produced in experiments according to graduated marks on apparatus

Question 14

avoid parallax error

Answer 14

always take reading at the bottom of the liquid meniscus (exception: take reading at top of the meniscus of liquid mercury)

Question 15

collecting gases produced (3 types)

Answer 15

1. displacement of water
2. downward delivery (displacement of air)
3. upwards delivery (displacement of air)

Question 16

properties of gases that affect choice of method of collection [2pts + explanation]

Answer 16

1. solubility: how well a gas dissolves in water
2. density: how dense a gas is compared to air

Question 17

displacement of water (water displacement) [2pts + examples]

Answer 17

• used to collect gases which are insoluble to slightly soluble
• density does not affect gas collection
• example: oxygen, hydrogen, carbon dioxide

Question 18

downward delivery (displacement of air) [1pt + examples]

Answer 18

• used to collect gases denser than air and soluble or insoluble in water
• example: chlorine, hydrogen chloride, sulfur dioxide, carbon dioxide, nitrogen dioxide

Question 19

upward delivery (displacement of air) [1pt + examples]

Answer 19

• used to collect gases less dense than air and soluble or insoluble in water
• example: ammonia

Question 20

mass of air

Answer 20

Mr (relative molecular mass) = 29

Question 21

gas less dense than air

Answer 21

smaller Mr than 29

Question 22

gas denser than air

Answer 22

larger Mr than 29

Question 23

drying gases (definition)

Answer 23

- to obtain a dry sample of gas by removing its moisture content

Question 24

method for drying gases [3 types + formulas]

Answer 24

1. fused calcium chloride (CaCl₂) 2. concentrated sulfuric acid (H₂SO₄) 3. calcium oxide [quicklime] (Cao)

Question 25

fused calcium chloride (CaCl₂)

Answer 25

- used to dry most gases - example: hydrogen, nitrogen, carbon dioxide - not suitable: gases which react with calcium chloride, e.g. ammonia

Question 26

concentrated sulfuric acid (H₂SO₄)

Answer 26

- used to dry most gases, acidic gases - example: chlorine, hydrogen chloride (acidic gas, will not react) - not suitable: gases which react with sulfuric acid --> alkaline gas, e.g. ammonia

Question 27

calcium oxide [quicklime] (Cao)

Answer 27

- used to dry alkaline gases - example: ammonia - not suitable: gases which react with calcium oxide, e.g. carbon dioxide, sulfur dioxide