Chromatography and distillation

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課程筆記

Chromatography

Chromatography separates different substances in a mixture.
A spot of ink is placed on chromatography paper and the paper is placed in water.
Water rises up the paper and acts as a solvent.
Ink is made of different dyes that are soluble in water.
As water rises, it brings dyes up the paper; different dyes move at different rates.
Dyes that travel the same distance up the paper are the same dye.

The three steps of a paper chromatography experiment: spotting the sample on a pencil baseline, lowering the paper into solvent below the baseline, and analysing the separated spots on the chromatogram.

Simple Distillation

Simple distillation separates a liquid from a dissolved solid (e.g., salt from seawater).
A Bunsen burner heats the mixture; the liquid evaporates, leaving the solid behind.
Vapour travels through a condenser where cooling water passes.
The cool condenser condenses the vapour back to liquid, collected as distilled water.
This method can also separate liquids with different boiling points.

Simple distillation of salty water: water vapour rises from the flask, passes through the condenser (cooling water in at the beaker end, out at the flask end), and is collected as pure water.

Key Terms

Soluble: able to dissolve in a solvent.
Solvent: a liquid that dissolves a substance (e.g., water in chromatography).
Evaporation: change from liquid to gas.
Condensation: change from gas to liquid.

Common Misconceptions

In chromatography, ink is not the solvent; water is the solvent.
Chromatography separates mixtures, not elements in a compound.
Salt cannot be filtered from seawater because salt dissolves; distillation is needed.

Application: Separating Liquids

If two liquids have different boiling points, the one with the lower boiling point evaporates first.
Example: Liquid A (boiling point 100°C) will evaporate before Liquid B (300°C).

Fractional distillation of a water/ethanol mixture: the fractionating column allows repeated condensation and evaporation so the lower-boiling ethanol distils off first.

$Fractional distillation of a water/ethanol mixture: the fractionating column allows repeated condensation and evaporation so the lower-boiling ethanol distils off first.$

States of matter: solid, liquid, gas. Evaporation (liquid to gas) and condensation (gas to liquid) are key in distillation.

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練習題

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1.In chromatography, what is the solvent?
Easy
- AWater
- BInk
- CDye
- DPaper
2.Which statement about chromatography is correct?
Easy
- ADyes are soluble in the solvent.
- BThe solvent is the ink.
- CChromatography separates compounds into elements.
- DAll dyes move at the same rate.
3.What is the name of the state change from gas to liquid?
Easy
- ACondensation
- BEvaporation
- CBoiling
- DMelting
4.What is the name of the state change from liquid to gas?
Easy
- AEvaporation
- BCondensation
- CFreezing
- DSublimation
5.In simple distillation of seawater, what is left behind in the flask?
Easy
- ASalt
- BPure water
- CWater vapour
- DCondensed water
6.During simple distillation, what is the purpose of the cooling water in the condenser?
Easy
- ATo condense the vapour into liquid
- BTo evaporate the liquid
- CTo heat the vapour
- DTo dissolve the salt
7.A mixture of two liquids is distilled. Liquid A boils at 100°C, liquid B at 300°C. Which liquid is collected first?
Easy
- ALiquid A
- BLiquid B
- CBoth together
- DNeither
8.Why can't salt be removed from seawater by filtration?
Easy
- ASalt particles are too small to be trapped by filter paper
- BSalt is insoluble in water
- CFilter paper dissolves in seawater
- DFiltration only works for gases

更多題目

9.In chromatography, what does it mean if two inks have a dye that travels the same distance?
Easy
- AThey contain the same dye
- BThey are the same colour
- CThey have the same number of dyes
- DThey are both soluble
10.What does the term 'soluble' mean?
Easy
- AAble to dissolve in a solvent
- BUnable to dissolve
- CAble to be filtered
- DAble to evaporate
11.What does the term 'solvent' mean?
Easy
- AThe liquid that dissolves a substance
- BThe substance that dissolves
- CThe solid left behind
- DThe paper used in chromatography
12.A student performs chromatography on a mixture of three dyes using water as the solvent. After the experiment, the chromatogram shows three spots at different heights. Which conclusion is correct?
Medium
- AThe dye with the highest spot is the most soluble in water.
- BThe dye with the highest spot is the least soluble in water.
- CThe dye with the lowest spot is the most soluble in water.
- DAll dyes have the same solubility in water.
13.A mixture of two liquids, X and Y, is separated by simple distillation. The boiling point of X is 78°C and that of Y is 100°C. The distillate collected first is X. What is the most likely reason for this?
Medium
- AX has a lower boiling point than Y, so it evaporates first.
- BX has a higher boiling point than Y, so it condenses first.
- CX has a lower density than Y, so it rises first.
- DX is less volatile than Y, so it evaporates first.
14.In a chromatography experiment, a red dye and a blue dye are separated. The red dye travels 4 cm and the blue dye travels 6 cm from the starting line. The solvent front is 10 cm. What is the Rf value of the blue dye?
Medium
- A0.4
- B0.6
- C0.67
- D1.67
15.In a simple distillation setup, a condenser is used. What is the main function of the condenser?
Easy
- ATo heat the mixture.
- BTo cool and condense the vapour back into liquid.
- CTo separate the mixture by filtration.
- DTo increase the pressure in the apparatus.
16.A student performs chromatography on a mixture of four dyes. The chromatogram shows four spots. Which statement about the dyes is correct?
Medium
- AAll dyes are pure substances.
- BThe dyes are separated based on their boiling points.
- CThe dyes are separated based on their solubility in the solvent.
- DThe dyes are separated based on their colour.
17.A mixture of ethanol (boiling point 78°C) and water (boiling point 100°C) is distilled. Which substance is collected first and why?
Medium
- AWater, because it has a higher boiling point.
- BEthanol, because it has a lower boiling point.
- CEthanol, because it is less dense.
- DWater, because it is more soluble.
18.In the chromatography diagram from the source, which two inks share a common dye?
Medium
- AOrange and purple
- BOrange and green
- CPurple and green
- DAll three share a common dye
19.A student wants to obtain pure water from seawater. Which method should they use?
Easy
- AFiltration
- BChromatography
- CSimple distillation
- DEvaporation alone
20.In a chromatography experiment, a spot of ink is placed on the baseline and the solvent is allowed to run. After drying, the chromatogram shows two spots: one at 2.5 cm and one at 5.0 cm from the baseline. The solvent front is 10.0 cm. What is the Rf value of the slower-moving dye?
Medium
- A0.25
- B0.50
- C0.75
- D2.5
21.A student claims that salt can be removed from seawater by filtration. Why is this incorrect?
Medium
- ASalt particles are too large to pass through filter paper.
- BSalt dissolves in water, forming a solution that passes through filter paper.
- CFiltration only separates insoluble solids from liquids.
- DBoth B and C are correct.
22.What is the state change called when a gas turns into a liquid?
Easy
- AEvaporation
- BCondensation
- CMelting
- DFreezing
23.In simple distillation, what is the purpose of the cooling water in the condenser?
Easy
- ATo heat the vapour.
- BTo cool the vapour so it condenses.
- CTo dissolve any impurities.
- DTo increase the rate of evaporation.
24.In a chromatography experiment, a spot of ink is placed on the baseline and the solvent is allowed to run. After drying, the chromatogram shows two spots: one at 2 cm and one at 5 cm from the baseline. The solvent front travelled 10 cm. What is the Rf value of the faster-moving dye?
Medium
- A0.5
- B0.2
- C0.4
- D0.8
25.A student performs chromatography on a mixture of three dyes using water as the solvent. After the experiment, the chromatogram shows three spots at different heights. Which statement about the dyes is correct?
Medium
- AAll three dyes are different from each other.
- BTwo of the dyes are the same.
- CAll three dyes are the same.
- DThe dye that travelled the least is the most soluble.
26.A mixture of two liquids, X and Y, is separated by simple distillation. The boiling point of X is 78°C and that of Y is 100°C. The distillate collected first is:
Easy
- AX, because it has a lower boiling point.
- BY, because it has a higher boiling point.
- CX, because it is less dense.
- DY, because it condenses more easily.
27.What is the state change called when a liquid turns into a gas?
Easy
- AEvaporation
- BCondensation
- CFreezing
- DDeposition
28.In chromatography, what is the role of the paper?
Easy
- AIt acts as the stationary phase
- BIt acts as the mobile phase
- CIt is the solvent
- DIt is the solute
29.Which statement about simple distillation is correct?
Easy
- AIt separates mixtures based on differences in boiling points
- BIt separates mixtures based on differences in solubility
- CIt uses a filter to separate solids from liquids
- DIt uses a centrifuge to separate liquids
30.What is the name of the process when a liquid turns into a gas?
Easy
- AEvaporation
- BCondensation
- CMelting
- DSublimation
31.In the chromatography diagram from the source, how can you tell that two inks share a common dye?
Medium
- AThe dye has risen by the same amount up the chromatography paper
- BThe inks are the same colour
- CThe dyes have different colours
- DThe solvent travels the same distance
32.A student performs simple distillation on a mixture of ethanol (boiling point 78°C) and water (boiling point 100°C). Which substance is collected first?
Easy
- AEthanol, because it has a lower boiling point
- BWater, because it has a higher boiling point
- CEthanol, because it has a higher boiling point
- DWater, because it has a lower boiling point
33.In a chromatography experiment, the solvent front travels 10 cm and a dye spot travels 6 cm from the baseline. What is the Rf value of that dye?
Medium
- A0.6
- B1.67
- C6.0
- D0.4
34.In simple distillation, what is the purpose of the condenser?
Easy
- ATo cool and condense the vapour back into liquid
- BTo heat the mixture
- CTo filter out impurities
- DTo increase the boiling point
35.A chromatogram shows four spots from a mixture. Two spots have the same Rf value. What does this indicate?
Medium
- AThe two spots are the same substance
- BThe two spots are different substances
- CThe solvent front was not measured correctly
- DThe paper was not placed vertically
36.In the chromatography diagram from the source, which two inks do NOT share a common dye?
Medium
- AOrange and purple
- BOrange and green
- CPurple and green
- DAll three inks share at least one common dye
37.In a chromatography experiment, a solvent front travels 12 cm and a dye spot travels 7.2 cm from the baseline. What is the Rf value of that dye?
Medium
- A0.60
- B1.67
- C0.60 cm
- D7.2 cm
38.A student performs chromatography on a mixture of three dyes using water as the solvent. After the experiment, the chromatogram shows three spots at different heights. The student measures the distance from the baseline to each spot: spot A = 2.0 cm, spot B = 5.0 cm, spot C = 8.0 cm. The solvent front travelled 10.0 cm. Which spot is the most soluble in water?
Medium
- ASpot A
- BSpot B
- CSpot C
- DAll are equally soluble
39.In chromatography, the ink is the solvent.
Easy
True or false?
40.In chromatography, the dyes are soluble in water.
Easy
True or false?
41.Chromatography allows us to separate different elements in a compound.
Medium
True or false?
42.Simple distillation allows us to separate liquids with different boiling points.
Easy
True or false?
43.Cooling water is used in a condenser to condense hotter gases.
Easy
True or false?
44.A mixture of liquids undergoes simple distillation. Liquid A has a boiling point of 100°C. Liquid B has a boiling point of 300°C. As the mixture is heated, which liquid will evaporate and be collected first?
Easy
- ALiquid A
- BLiquid B
- CBoth at the same time
- DNeither
45.Match each separation method to its correct description.
Medium
- Chromatography
- Simple distillation
- Separates mixtures based on different boiling points
- Separates mixtures based on different rates of movement through a medium
46.Place the steps of simple distillation in the correct order.
Medium
- Heat the mixture to boil the liquid with the lower boiling point
- The vapour passes into the condenser
- Cool water circulates around the condenser to condense the vapour
- Collect the distilled liquid
47.Which of the following statements about chromatography are correct? (Select all that apply)
Medium
- AThe solvent must be a liquid
- BThe substances being separated must be soluble in the solvent
- CThe paper is placed with the solvent above the starting line
- DDifferent dyes travel at different rates
48.In a chromatography experiment, a mixture of three dyes is separated using water as the solvent. The solvent front travels 12 cm from the baseline. Dye A travels 4 cm, dye B travels 8 cm, and dye C travels 10 cm. Which dye is the most soluble in the solvent?
Medium
- ADye A
- BDye B
- CDye C
- DCannot be determined
49.Complete the sentence with the correct term.
Easy
The state change from gas to liquid is called ____.
50.Describe what the word 'soluble' means.
Easy
51.Describe what the word 'solvent' means.
Easy
52.In a chromatography experiment, the solvent front travels 15 cm and a dye spot travels 9 cm from the baseline. Calculate the Rf value of the dye. Give your answer to two decimal places.
Medium
53.Complete the sentences about simple distillation.
Easy
In simple distillation, the liquid with the ____ boiling point evaporates first. The vapour is then ____ in the condenser.
54.In a chromatography experiment, the solvent front travels 15 cm from the baseline. A dye spot is found 9 cm from the baseline. Calculate the Rf value of the dye. Give your answer to two decimal places.
Medium
55.A mixture of two liquids, X and Y, is separated by simple distillation. Liquid X has a boiling point of 78°C and liquid Y has a boiling point of 100°C. Which liquid is collected first?
Easy
56.Describe how chromatography is used to separate dyes in an ink.
Medium
57.A student claims that salt can be filtered out of seawater by passing seawater through filter paper. Explain why the student is wrong and describe a correct method for obtaining pure water from seawater.
Hard
58.In a chromatography experiment, the solvent front travels 15 cm and a dye spot travels 9 cm from the baseline. Calculate the Rf value of the dye. Give your answer to two decimal places.
Medium
- A1.6
- B-0.4
- C0.6
- D2.6
59.In a chromatography experiment, the solvent front travels 15 cm from the baseline. A dye spot is found 9 cm from the baseline. Calculate the Rf value of the dye. Give your answer to two decimal places.
Medium
- A-0.4
- B2.6
- C0.6
- D1.6

複習筆記

## Chromatography and Distillation ### Chromatography - **Purpose**: Separates different substances in a mixture (e.g., dyes in ink). - **Method**: Place a spot of ink on chromatography paper; put paper in water (solvent). Water rises, carrying soluble dyes. Different dyes move at different rates, so they separate. - **Key fact**: If two inks have a dye that rises the same distance, they share that dye. - **Terms**: - **Soluble**: Can dissolve in a solvent. - **Solvent**: The liquid that dissolves a substance (here, water). ### Simple Distillation - **Purpose**: Separates a liquid from a solid (e.g., pure water from seawater) or liquids with different boiling points. - **Method**: Heat mixture (e.g., seawater). Water evaporates (liquid → gas), leaving salt behind. Vapour passes through a condenser cooled by water, condensing it back to liquid (gas → liquid). Collect distilled water. - **Boiling points**: When separating two liquids, the one with the lower boiling point evaporates and collects first. Example: Liquid A (bp 100°C) will be collected before Liquid B (bp 300°C). ### State Changes - **Condensation**: Gas → Liquid (occurs in condenser). - **Evaporation**: Liquid → Gas (occurs when heating). ### Common Mistakes - **Filtering seawater**: Salt dissolves in water, so it passes through filter paper. Use distillation to obtain pure water. - **Chromatography**: Ink is NOT the solvent; water is. Chromatography separates mixtures, not elements in a compound.

Chromatography: A method to separate different substances in a mixture based on their different rates of movement through a medium.
Distillation: A process that separates a liquid from a solid or other liquids by heating to evaporate and then condensing the vapour.
Soluble: Able to be dissolved in a solvent.
Solvent: A liquid that dissolves a substance (e.g., water in chromatography).
Condensation: The change of state from gas to liquid.
Evaporation: The change of state from liquid to gas.
Condenser: A device that cools gas to condense it into liquid.

字卡

What is chromatography used for?

Chromatography allows us to separate different substances in a mixture.

In chromatography, what is the solvent?

In chromatography, water acts as the solvent.

Why do different dyes separate during chromatography?

Different dyes move up the chromatography paper at different rates, so they separate.

How can you tell if two inks share a common dye using chromatography?

If a dye rises by the same amount up the chromatography paper for both inks, they have that dye in common.

What is simple distillation used for?

Simple distillation can separate a liquid from a dissolved solid, or separate liquids with different boiling points.

Describe the simple distillation apparatus for seawater.

A Bunsen burner heats seawater, water evaporates leaving salt behind, water vapour travels through a condenser cooled by water, and distilled water is collected.

What is the role of the condenser in distillation?

The condenser is cool and condenses water vapour back into liquid water.

True or false: In chromatography, ink is the solvent.

False. In chromatography, water is the solvent, not ink.

True or false: In chromatography, the dyes are soluble in water.

True.

True or false: Chromatography allows us to separate different elements in a compound.

False. Chromatography separates substances in a mixture, not elements in a compound.

True or false: Simple distillation allows us to separate liquids with different boiling points.

True.

True or false: Cooling water is used in a condenser to condense hotter gases.

True.

What is the state change from gas to liquid called?

Condensation.

What is the state change from liquid to gas called?

Evaporation.

What does 'soluble' mean?

Soluble means a substance can dissolve in a solvent.

What does 'solvent' mean?

A solvent is a liquid that dissolves other substances.

A mixture of liquids A (boiling point 100°C) and B (boiling point 300°C) undergoes simple distillation. Which liquid evaporates and is collected first?

Liquid A evaporates first because it has a lower boiling point.

Describe how chromatography is used to separate dyes in an ink.

A spot of ink is placed on chromatography paper, which is placed in water. Water rises up the paper, carrying dyes at different rates, separating them.

Can salt be filtered out of seawater using filter paper? Explain.

No, because salt dissolves in water to form a solution, so it passes through filter paper. Distillation is a correct method to obtain pure water from seawater.

What is the correct method to obtain pure water from seawater?

Simple distillation: heat seawater to evaporate water, then condense the vapour to collect pure water.

What is the purpose of the Bunsen burner in simple distillation?

The Bunsen burner applies heat to the mixture to cause evaporation.

What happens to the salt in seawater during simple distillation?

The salt remains behind in the flask because it does not evaporate.

What is the collected liquid in simple distillation of seawater called?

Distilled water.

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