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Pure Chemistry (Sec 3) > Chapter 01 - Experimental Chemistry > Flashcards

Chapter 01 - Experimental Chemistry Flashcards

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1
Q

What are the 5 physical properties that can be measured?

A

Mass, Temperature, Time, Volume, Length

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2
Q

What is the SI unit for mass?

A

Kilogram (kg)

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3
Q

Name 2 other units for mass

A

Miligram (mg), Gram (g), tonnes (t)

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4
Q

What are 2 instruments to measure mass?

A

beam balance, electronic balance

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5
Q

1 kg = ? g = ? mg

A

1 kg = 1000g = 1000000 mg

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6
Q

1 t = ? kg

A

1 t = 1000 kg

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7
Q

What is the SI unit for length?

A

Metre (m)

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8
Q

Name 2 other units for length

A

Centimeters (cm),
Kilometers (km), Decimetre (dm), Milimetre (mm)

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9
Q

What are the 2 apparatus to measure length?

A

Metre rule & Measuring tape

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10
Q

How much does the metre rule measure? (Hint: A few ____ to up to ____)

A

Measures lengths from a few centimetres to one metre

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11
Q

How much does the measuring tape measure? (Hint: A few ____ to up to ____)

A

Measures lengths from a few centimetres to a few metre

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12
Q

1 m = ? dm = ? cm = ? mm (Hint: There’s a pattern)

A

1 m = 10 dm = 100 cm = 1000 mm

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13
Q

What is the accuracy of a metre rule?

A

0.1 cm

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14
Q

What is the accuracy of a measuring tape?

A

0.1cm to 0.5 cm

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15
Q

What is the SI unit for time?

A

Second (s)

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16
Q

What are 2 apparatus to measure time?

A

Mechanical stopwatch, Digital stopwatch, Hourglass

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17
Q

1 hour = ? min = ? s

A

1 hour = 60 min - 3600 s

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18
Q

What is the SI unit of temperature?

A

Kelvin (K)

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19
Q

What are 2 instruments to measure temperature?

A

Alcohol thermometer, Digital laboratory thermometer, Oral digital thermometer

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20
Q

What are 2 other units for temperature?

A

Degree Celsius (°C), Degree Fahrenheit (°F)

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21
Q

What is the conversion between K and °C?

A

Temperature in K = Temperature in °C + 273

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22
Q

What is the SI unit for volume?

A

Cubic metre (m³)

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23
Q

What apparatus is used to measure gas?

A

Gas syringe

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24
Q

What apparatus is used to measure volume?

A

Burette, Measuring cylinder, Pipette, Volumetric flask, Gas syringe

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25
Q

What are the parts of a gas syringe?

A

Plunger, Barrel, Plunger tip, Scale

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26
Q

A gas syringe can not only collect gases, but also…

A

measure them

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27
Q

Does a burette measure a fixed volume or a range of volumes?

A

A range of volumes

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28
Q

What is the degree of accuracy for a burette?

A

To the nearest 0.05cm³ (e.g. 27.35 cm³, 34.00 cm³)

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29
Q

Does a measuring cylinder measure a fixed volume or a range of volumes?

A

A range of volumes

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30
Q

What is the degree of accuracy for a measuring cylinder?

A

To the nearest 0.5 cm³ (e.g. 6.5 cm³, 27.0 cm³)

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31
Q

Does a pipette measure a fixed volume or a range of volumes?

A

Accurate fixed volumes (e.g. 10.0 cm³, 20.0 cm³, 25.0 cm³)

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32
Q

Does a volumetric flask measure a fixed volume or a range of volumes?

A

Accurate fixed large volumes (e.g. 100 cm³, 250 cm³)

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33
Q

What is a meniscus?

A

An upward/downward curve at the top of a liquid or a solution

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34
Q

Which error would you avoid by reading the meniscus accurately?

A

Parallax error

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35
Q

How do you read a volume by a meniscus accurately?

A

Make sure your eye level is at the same level as the meniscus and read the bottom/top of the curve.

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36
Q

What are the 3 ways gases can be collected?

A

Displacement of air, Displacement of water, Gas syringes

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37
Q

What are the 2 properties of gases that decide the choice of collection?

A

Solubility & Density of gas

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38
Q

What are the two types of displacement of air?

A

Downward & Upward delivery

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39
Q

Is downward delivery used to collect gases denser than air or less dense than air?

A

Denser than air

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40
Q

Name 2 gases that are denser than air

A

Chlorine, Hydrogen chloride, Sulfur dioxide, Carbon dioxide, Nitrogen monoxide

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41
Q

How does downward delivery work? (Hint: The test tube is place at an ____ position. The produced gas ____ down into the test tube and displaces the air inside it)

A

The test tube is place at an upright position. The produced gas sinks down into the test tube and displaces the air inside it

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42
Q

Is upward delivery used to collect gases denser than air or less dense than air?

A

Less dense than air

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43
Q

Name 2 gases that are less dense than air

A

Hydrogen, Ammonia

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44
Q

How does upward delivery work? (Hint: The test tube is place at an ____ position. The produced gas ____ up into the test tube and displaces the air inside it)

A

The test tube is place at an inverted position. The produced gas rises up into the test tube and displaces the air inside it

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45
Q

Displacement of water is only suitable for gases that are… (Hint: there are two key points)

A

Insoluble or slightly soluble in water & Has the same density as air

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46
Q

Name 2 gases that are suitable for water displacement

A

Hydrogen, Oxygen, Carbon Dioxide

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47
Q

What do drying agents do? (Hint: Drying agents are used to obtain ____ by ____)

A

Drying agents are used to obtain a dry sample of a gas by removing its moisture content

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48
Q

What are the 3 drying agents?

A

Fused calcium chloride, Concentrated sulfuric acid, Calcium oxide

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49
Q

What gases does FCC dry?

A

ALL gases except ammonia

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50
Q

What gases does CSA dry?

A

ALL gases except alkaline gases (e.g. ammonia)

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51
Q

What gases does CO dry?

A

ALL gases except acidic gases (e.g. Sulfur dioxide)

52
Q

What is a pure substance?

A

A substance that only contains one type of substance, can be an element or a compound

53
Q

A pure substance will change from solid to liquid at a ____ temperature known as the ____

A

A pure substance will change from solid to liquid at a fixed temperature known as the melting point

54
Q

A pure substance will change from liquid to gas at a ____ temperature known as the ____

A

A pure substance will change from solid to liquid at a fixed temperature known as the boiling point

55
Q

An impure substance will melt ____ the melting point ____

A

An impure substance will melt below the melting point over a range of temperatures. The greater the amount of impurities in a substance, the lower the temperature the substance melts below the melting point.

56
Q

An impure substance will boil ____ the boiling point ____

A

An impure substance will boil above the boiling point over a range of temperatures. The greater the amount of impurities in a substance, the higher the temperature the substance boils above the boiling point.

57
Q

It has 2 or more substances that are not chemically joined together, and is not pure. What is it?

A

A mixture (e.g. seawater, petroleum, air, salt solution, alloys)

58
Q

What do physical separating methods do?

A

They separate mixtures, one substance from the other without changing the chemical composition of the substances

59
Q

How do you choose which physical methods to use to separate substances?

A

By the physical properties in the substance

60
Q

What are the 3 natures of separation method?

A

Solid-Solid, Solid-Liquid, Liquid-Liquid

61
Q

What are the 4 methods for Solid-Solid separation?

A

Magnetic attraction, Sieving, Using suitable solvents, Sublimation

62
Q

How does magnetic attraction separate substances in a mixture?

A

Magnets attract magnetic substances from non magnetic substances in a mixture

63
Q

Name 2 common magnetic substances

A

Iron, Nickel, Cobalt, Steel (Alloy)

64
Q

How does sieving separate substances in a mixture?

A

A sieve separates substances in a mixture based on particle size - only particles smaller than the pore size can pass through

65
Q

What type of substances are particles with smaller size referred to?

A

Fine substances

66
Q

What type of substances are particles with large size referred to?

A

Coarse substances/Lumps

67
Q

How does using suitable solvents separate substances in a mixture?

A

When a mixture contains only one soluble solid, a suitable solvent is used to dissolve the soluble solid, separating it from the insoluble solids

68
Q

What is a solute?

A

A substance that dissolves in a solvent

69
Q

What is a solvent?

A

A substance that dissolves a solute

70
Q

What does solubility mean?

A

Solubility refers to the ability of a solute to dissolve in a solvent

71
Q

What does it mean when a substance sublimes?

A

It means the substance changes from solid state to gas state directly without melting

72
Q

How does sublimation separate substances in a mixture?

A

When a mixture contains a substance that can sublime, heating is carried out to separate it from others in the mixture

73
Q

Name 2 common substances that sublime

A

Iodine crystals, Dry ice, Naphthalene

74
Q

When a substance sublimes, it’s vapour changes back into ____ known as the ____

A

When a substance sublimes, it’s vapour changes back into solid deposit known as the sublimate

75
Q

What are the 4 methods for Solid-Liquid separation?

A

Filtration, Evaporation to dryness, Crystallisation, Simple distillation

76
Q

How does filtration separate substances in a mixture?

A

The liquid/solution has smaller particle size than the pores on the filter paper, hence being able to pass through while the insoluble solids particle size is too large to pass through the pores of the filter paper

77
Q

What is the substance collected on the filter paper called?

A

Residue

78
Q

What is the substance collected in the flask called?

A

Filtrate

79
Q

How does evaporation to dryness separate substances in a mixture?

A

If the soluble solid is heat stable, evaporation is used by heating the solution to dryness, the solid remains crystallined residue after the solvent has evaporated

80
Q

How does crystallisation separate substances in a mixture?

A

When a soluble solid is not heat stable, the solution will be heated until it becomes a saturated solution which will be left to cool

81
Q

What is a saturated solution?

A

A type of solution in which no more solute can dissolve in it

82
Q

If the cooling process takes place quickly, how does it affect the size of the crystals?

A

The crystals will be smaller and powdery

83
Q

If the cooling process takes place slowly, how does it affect the size of the crystals?

A

The crystals will be bigger

84
Q

How does simple distillation separate substances in a mixture?

A

The liquid is heated to reach its boiling point to become a vapour which is then cooled by a condenser, changing back into a liquid. It is then collected in the receiver as a distillate

85
Q

What happens to the impurities in the liquid during fractional distillation?

A

They remain in the flask because they have much higher boiling points

86
Q

What is the reason for boiling chips?

A

Smoother boiling to prevent bumping

87
Q

Why is a conical flask used instead of a beaker to collect the distillate?

A

Due to the conical flask’s narrow neck which reduces the loss of distillate from splashing out of the flask

88
Q

What can be done to prevent a distillate from evaporating if it is volatile?

A

The receiving flask can be placed in a water bath to shield the heat from the heat source

89
Q

Why does the water in the condenser flow in the opposite direction?

A

To ensure a permanent cold surface to condense the vapour effectively

90
Q

How does paper chromatography separate substances in a mixture? (warning, many questions about paper chromatography ahead)

A

Paper chromatography separates mixtures based on the extent of solubility of different substances in a solvent. When a substance dissolves in a solvent, it will be carried along by the solvent on the chromatography paper

91
Q

What is referred to as the mobile phase?

A

The solvent that moves across the chromatography paper

92
Q

What is referred to as the stationary phase?

A

The chromatography paper

93
Q

The ____ soluble the substance in the solvent, the ____ it travels

A

more, further

94
Q

What are the 6 parts of basic paper chromatography and their functions?

A

1) Spot - shows the component in the sample
2) Starting line - marks the position in which the sample is placed
3) Solvent - to dissolve the sample
4) Chromatography paper - allows the separation of the components in the sample
5) Solvent front - marks the end position of the solvent travelling on the paper
6) Lid - to prevent the evaporation of the solvent

95
Q

What are the 5 basic steps in carrying out paper chromatography?

A

1) Use a pencil to draw a starting line
2) The sample is placed at the starting line
3) The paper is dipped into a solvent below the starting line
4) The solvent is absorbed into the paper and rises up, separating the components in the sample
5) The chromatogram shows the components in the sample

96
Q

Why should the solvent front not travel to the edge of the paper?

A

Prevents the components of the sample being unaccountable on the chromatogram and allows actual distance travelled by solvent to be measured

97
Q

Why should the solvent front be as high as possible?

A

Allows all the components to be fully separated

98
Q

Why should the starting line be drawn in graphite pencil instead of pen?

A

As the graphite pencil is insoluble in the solvent, it will not be carried by the solvent to interfere the results. Additionally ink is made up of different dyes that dissolves in solvents, separating into different components, pencil does not have ink

99
Q

Why should the sample applied be as small as possible?

A

The tailing and smudging of different components will not occur so that we can identify the respective spots easily

100
Q

Why should the starting line be above the solvent?

A

This prevents the sample from dissolving in the solvent so that the components in the sample can be moved along by the solvents on the chromatography paper

101
Q

Why should the beaker containing the solvent be covered by a lid?

A

To prevent evaporation of the solvent and maintain its saturation of the solvent vapour so that the solvent will not evaporate from the paper too quickly

102
Q

When a sample remains at the starting line, what does it tell us about the sample?

A

It does not dissolve in the solvent

103
Q

What are the 4 things we can deduce from a chromatogram?

A

1) The number of spots which indicate the number of substances in the sample
2) Any spots which are horizontally matched are likely the same substance
3) A single spot produced by a sample indicates that the sample is a pure substance
4) Two or more spots produced by a sample indicate that the sample is a mixture

104
Q

What are 2 advantages of using paper chromatography?

A

Gives quick and accurate analysis of sample, requires a small amount of sample, able to separate complex mixtures

105
Q

What are the 2 ways to identify components in paper chromatography?

A

Compare to ‘known samples’ or compare their Rf values

106
Q

What is the Rf value?

A

Rf value is the distance of a substance travelled compared to the distance travelled by the solvent

107
Q

What is the formula for Rf value?

A

Distance travelled by a spot /
Distance travelled by the solvent

108
Q

When is a locating agent used?

A

When separated components on a chromatogram are invisible

109
Q

What are the 2 locating agents?

A

Ninhydrin and Ultraviolet light (UV)

110
Q

When is Ninhydrin used?

A

When a protein sample is broken down, colourless/invisible amino acids are released. Ninhydrin is added to react with the amino acids to produce coloured substances

111
Q

When is UV used?

A

UV light is used on colourless components that fluoresce (shine or glow brightly) under UV light

112
Q

How to tell if a substance is pure using a chromatogram?

A

A pure substance will only have one spot while an impure substance will have more than 1 spot

113
Q

Name 2 industries that paper chromatography is widely used in

A

1) Detecting a small amount of banned substances in an athlete’s urine or blood samples
2) Monitoring the use of artificial flavourings and colourings in the food industry
3) Collecting evidence of crimes such as identifying DNA fragments

114
Q

How does fractional distillation separate components in a mixture?

A

Fractional distillation separates miscible liquids based on different boiling points

115
Q

What are miscible liquids?

A

Miscible refers to two or more liquids that mix completely together to form a uniform/homogenous solution without separating into two different layers

116
Q

What does the tall fractionating column consist of?

A

The tall fractionating column consists of glass beads which increase the surface area to volume ratio for evaporation and condensation of vapour to separate different liquids accurately and efficiently

117
Q

The column is hottest at the ____ and cools gradually towards the ____

A

The column is hottest at the bottom and cools gradually towards the top

118
Q

The liquid with the lower boiling point boils and distills ____ while the liquid with the ____ boiling point boils and distills ____

A

The liquid with the lower boiling point boils and distills first while the liquid with the lower boiling point boils and distills second

119
Q

What happens when a vapour reaches a part of the fractionating column that where the temperature is lower than its boiling point

A

It condenses and drips back into the distillation flask

120
Q

What happens when a vapour reaches a part of the fractionating column that where the temperature is higher than its boiling point

A

It will continue to rise up and into the condenser and condense

121
Q

What must we do to the collecting flask when the temperature starts to increase over the boiling point of the first distillate?

A

We must remove it to avoid contamination of the two liquids because it means that all of the first distillate has been collected completely and that the second liquid will start to distill

122
Q

The closer the boiling points of the different liquids, the ____ the fractionating column should be to separate them efficiently

A

The closer the boiling points of the different liquids, the taller the fractionating column should be to separate them efficiently

123
Q

Name 2 industries fractional distillation is used in

A

1) Separation of liquid air
2) Separation of crude oil
3) Separation of ethanol from fermented solution

124
Q

How does the separating funnel separate different components in a mixture?

A

Separating funnels separate liquids that are immiscible with different densities

125
Q

What is an immiscible mixture?

A

Immiscible mixtures refer to two or more liquids that do not mix completely, separating into two different layers (phases) and form a heterogenous mixture

126
Q

The liquid with a higher density will form the ____ layer, while the liquid with the lower density will form the ____ layer

A

The liquid with a higher density will form the lower layer, while the liquid with the lower density will form the upper layer

127
Q

How does the separating funnel work?

A

1) The mixture forms two layers in the funnel
2) The tap is opened and the lower layer is drained off into a beaker
3) The tap is closed once the lower layer has been completely drained off

Pure Chemistry (Sec 3) (2 decks)

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