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Chemistry 2022 > Measurement and Experimental Techniques and Separation Techniques > Flashcards

Measurement and Experimental Techniques and Separation Techniques Flashcards

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1
Q

what is the S.I. unit for mass?

A

kilogram (kg)

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2
Q

What apparatuses are used to measure mass?

A 
beam balance
electronic balance (+/- 0.01g)
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3
Q

what is the S.I. unit for time?

A

second (s)

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4
Q

what apparatuses are used to measure time?

A 
analogue stopwatch (0.1s)
digital stopwatch (0.001s)
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5
Q

what is the S.I. unit for temperature?

A

kelvin (K)

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6
Q

what apparatuses can be used to measure temperature?

A 
mercury thermometer (0.5 C)
alcohol thermometer (0.5 C)
data logger can be used to give more accurate readings of temperature. we can use it to record and study the changing temperture of a substance being heated or cooled loiver a period of time. Commonly used for taking temperatures outdoors
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7
Q

What is the S.I. unit for volume?

A

cubic metre (m3)

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8
Q

what apparatuses can be used to measure volume?

A

measuring cylinder (0.5)
burette (0.05)
pipette (fixed volumes of liquids, e.g. 20.0cm / 25.0cm)

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9
Q

how do we read the volume of a liquid?

A

we read at the bottom/top of the meniscus

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10
Q

what is a meniscus?

A

when water or a solution is placed in a comtainer, it forms a curved surface called a meniscus.

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11
Q

how do we measure volumes of gases?

A

with a gas syringe. it measurtes up to 100cm3

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12
Q

what are the 3 main methods for collecting gas?

A

displacement of water
downward delivery
upward delivery

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13
Q

what kind of gases can the method displacement of water collect

A

displacement of water is suitable for collecting gases that are insoluble or slightly insoluble in water.
e.g. carbon dioxide, hydrogen, oxygen

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14
Q

what kind of gases can the method downward delivery collect

A

downward delivery is used to collect gases that are soluble in water and denser than air
e.g. chlorine, hydrogen chloride

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15
Q

what kind of gases can the method upward delivery collect

A

upward delivery is used to collect gases that are soluble in water and less dense than air
e.g ammonia

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16
Q

how do you dry a gas?

A

we can dry a gas by passing it through a drying agent e.g. concentrated sulfric acid, quicklime, and fused calcium chloride

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17
Q

why is a gas that has been collected by displacement of water always damp?

A

the gas needs to pass through water, so it will always be damp

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18
Q

is density of the gas an important factor for displacement of water?

A

no. solubility of the gas is a more important factor to see if the gas dissolves in water or can be collected. the gas will still be collected even if its a denser or lighter gas

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19
Q

what apparatus is best used to measure the melting of a solid?

A

a thermometer

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20
Q

what apparatus is best used to collect and measure the volume of a water soluble gas?

A

a gas syringe

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21
Q

what apparatus is best used to add 17.30cm3 of solution to a flask?

A

burette

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22
Q

what apparatus is best used to separate a precipitate from a solution?

A

filter funnel

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23
Q

what apparatus is best used to measure exactly 22.7 cm3 of solution into a beaker?

A

burette

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24
Q

what apparatus is best used to add exactly 25 cm3 of solution to each of several beakers?

A

pipette

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25
Q

what is a pure substance?

A

a pure substance is made up of one single element or compound. it is not mixed with any substances.

26
Q

what is a mixture?

A

a mixture is made up of two or more substances that are not chemically combined together

27
Q

what is filtration?

A

filtration is a process used to separate insoluble solid particles from a liquid

28
Q

what are some mixtures where filtration is used?

A

sand and water
chalk powder and water
clay and water

29
Q

what is the solid that remains on the filter paper after filtration?

A

the residue

30
Q

what is the liquid or solution that passes through the filter paper during filtration?

A

the filtrate

31
Q

what are some real life uses for filtration?

A

coffee makers
water treatment
tea bag

32
Q

what is evaporation to dryness?

A

it is the process of obtaining a soluble solid from a solution by heating the solution until all the water has boiled off.

33
Q

what are some mixtures where evaporation to dryness can be used?

A

salt (sodium chloride) and water

34
Q

why could the solid obtained from evaporation to dryness be impure?

A

there might be soluble impurities left together with the solid

35
Q

what are some substances that cannot be obtained by evaporation to dryness?

A

sugar, it decomposes on heating

36
Q

what is crystallisation?

A

crystallisation is the process of obtaining a pure solid sample (soluble solid) from its solution

37
Q

why is crystallisation used to obtain a pure solid instead evaporation to dryness for some substances?

A

if substance could decompose on heating or could lose its water of crystallisation it should not be evaporated to dryness

38
Q

describe the procedure of crystallisation

A
  1. solution is heated to remove most of the solvent
  2. heating is stopped when a saturated solution is formed
  3. the hot saturated solution is allowed to cool and crystals are formed
  4. filter to obtain the crystals
  5. wash the crystals with little cold distilled water
  6. dry the crystals between sheets of filter paper
39
Q

what is the definition of saturated

A

a solution that contains as much dissolved solute as it can at a given temperature

40
Q

how do we test for saturation?

A
  1. a clean and dry glass rod is dipped and removed from the solution.
  2. if small crystals form on the rod when the solution cools, the solution is saturated
    a saturated solution is also known as a solution at its saturation point or crystallisation
41
Q

how can we separate solids?

A
  1. adding a suitable solvent and filtration
    (use a solvent in which only one solid is soluble)
  2. Magnetic attraction
    (used to separate magnetic substances e.g. iron, nickel, colbalt, steel) from mixtures)
  3. sublimation
    (used to separate a solid that sublimes from one that does not)
42
Q

how does sublimation separate solids?

A

a solid sublimes from one that does not

an inverted filter funnel is used to collect the substance that sublimed

43
Q

what is the definition of sublimination

A

when a solid turns into a gas without going through a liquid stage

44
Q

what are some substances that sublime

A

dry ice (solid carbon dioxide)
iodine
ammonium chloride

45
Q

what is simple distillation?

A 
a process that separates a pure solvent from a solution
pure water (solvent) can be obtained from a salt solution by simple distillation
46
Q

what are some substances that go through simple distillation

A

seawater
salt solution (sodium chloride)
sugar solution

47
Q

what is the use of a thermometer in simple distillation?

A

a thermometer measures the boiling point of the substance that is being distilled

48
Q

what is the use of a condenser in distillation?

A

The condenser cools the water vapors and condenses them back into pure water (distillate) into the reciever
cold running water enters from the bottom and leaves from the top
this ensures that the entire jacket is completely filled and this provides a more efficient cooling system

49
Q

what is the use of a reciever in distillation

A

collects the distillate
if the distillate is volatile, the reciever can be put into a container filled with ice, keeping the temperature of the distillate low so that it remains in the liquid state

50
Q

what is the use of boiling chips

A

to ensure smooth boiling

51
Q

when is a separating funnel used?

A

it is used when separating immiscible liquids (liquids that do not dissolve in each other e.g.oil and water)

52
Q

describe the procedure of using a separating funnel

A
  1. open the tap. pour the mixture into the separating funnel
  2. support the separating funnel using a retort stand
  3. allow liquid to separate. the denser liquid will be at the bottom layer
  4. open the tap to collect the denser liquid in a clean beaker. close the tap before the top layer of liquid runs out. open the tap to allow a little of the top layer of teh liquid into the beaker
  5. separating funnel now contains the less dense liquid
53
Q

when is fractional distillation used?

A

when separating miscible liquids (liquids that are soluble in each other) with different boiling points

54
Q

what are some mixtures that go through fractional distillation

A

ethanol and water
liquid air
crude oil

55
Q

what are some industrial applications that use fractional distillation?

A

obtain nitrogen, argon, and oxygen from air
separate crude oil into useful fractions
obtain ethanol from the fermentation mixture of water, glucose and malt to make alchoholic beverages

56
Q

what is paper chromatography?

A

paper chromatography is the method of separating two or more components that dissolve in the same solvent

57
Q

how does chromatography work?

A

separation of a substance into its different components depends on the relative solubility of the component. the more soluble component travels faster and further up the paper than the less soluble components. ( a dye that is more soluble in the solvent will travel further)
if there is only one spot on the chromatogram, the substance is pure.

58
Q

what is chromatography for?

A

to separate the components in a sample
identify the number of components in a sample
identify the components present in a sample
determine the purity of a sample

59
Q

why is it important to determine whether a substance is pure?

A

impurities in medicine may cause undesirable side effects
chemicals are often added to food and beverages. therefore it is important to ensure that our food contains only chemicals that are safe for consumption

60
Q

how do we determine the purity of a substance?

A

checking the melting point of a solid
checking the boiling point of a liquid
performing chromatography

61
Q

how do impurities affect the melting and boiling points of substances?

A

impurities lower the melting point (impurities cause melting/boiling to take place over a range of temperatures)
impurities increase the boiling point

62
Q

why must the start line be above the solvent level in chromatography

A

this is to prevent the sample spots from dissolving into the solvent instead of undergoing separation, which wil afect the accuracy of the results

Chemistry 2022 (3 decks)

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