C UNIT 1 > Water > Flashcards

Water Flashcards

(64 cards)

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1
Q

Where do our water supplies originate?

A

From rainwater

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2
Q

What gases dissolve in rainwater as it falls?

A

Carbon dioxide and Oxygen

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3
Q

What effect does dissolved Carbon Dioxide have on rainwater?

A

It lowers the pH, making the water slightly acidic

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4
Q

Why is dissolved Carbon Dioxide important in water bodies?

A

It helps plants carry out photosynthesis

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5
Q

Why is dissolved Oxygen important in water?

A

It allows aquatic organisms to respire

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6
Q

What happens to rainwater after it falls?

A

It runs through soil and rocka

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7
Q

What does water pick up from rocks?

A

It dissolves metal ions and minerals

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8
Q

What are common metal ions found in natural water?

A

Sodium, Potassium, Calcium, and Magnesium

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9
Q

What is abstraction?

A
  • A term to describe a away water is collected from natural source
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10
Q

What are reservoirs?

A

Man made lakes that are made using a dam to block a river and flood an area of land.

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11
Q

What is distribution?

A

After water is treated, it is sent to homes through pipes which are maintained regularly to preserve clean drinking water

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12
Q

What does untreated water contain?

A
  • Insoluble solids such as sand and mud
  • Contains a lot of microorganisms
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13
Q

What is the process of water treatment?

A

1) Screening
2) Sedimentation
3) Filtration
4) Chlorination
5) Storage

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14
Q

What is screening?

A

Protects and prevents large things from entering the reservoir, such as insoluble particles such as sand

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15
Q

What is sedimentation?

A

Cleaning the mud and others, insoluble particles falling to the bottom

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16
Q

What is filtration?

A

Pushes the water through sand, removing small insoluble particles

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17
Q

What is chlorination?

A

Eliminates and kills the germs, less then they’d add to swimming pools

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18
Q

What is storing?

A

Keeping all of the clean water and storing it for reservoirs

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19
Q

What is fluoridation?

A

The addition of small quantities of fluoride ions to drinking water in order to reduce tooth decay.

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20
Q

What are some negative views of fluoridation?

A
  • High concentrations of fluoride have been linked to dental fluorosis and bone cancer
  • Fluoride is already in tooth paste so more is not vital
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21
Q

What is distillation?

A

The process of separating miscible liquids with different boiling points

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22
Q

What is the process of

A

1) The solution is heated in a round-bottomed flask that is connected to a condenser.
2) The substance with the lowest boiling point starts to boil while any other substances are left behind in the flask.
3) The vapour of the boiled substance travels upwards through a tube until it reaches the condenser.
4) The vapour condenses back into a liquid when it comes into contact with the inner tube of the condenser, which is kept cold by a constant flow of cold water.

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23
Q

What is the separation of ethanol with a solution of ethanol in water?

A

An effective method as ethanol has a boiling point of 78, whilst water has a boiling point of 100, leaving the ethanol to boil first.

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24
Q

What is desalination?

A

A process that extracts drinkable water from sea water; essentially, removing the salt from the water.

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25
What is the simplest method for desalination? how is it carried out?
Distillation 1) The seawater is heated until the water starts to boil, forming water vapour. 2) The water vapour is collected, while the salt and other dissolved minerals are left behind. 3) The water vapour is cooled so that the vapour condenses back into liquid water.
26
What is another method of desalination?
- Membrane systems which work using osmosis
27
What do countries require to make desalination a viable water source?
- Access to the sea - Large amounts of money - A source of cheap energy
28
What is a solvent?
- A liquid that dissolves another substance - Water is the most commonly used solvent
29
What is a solute?
- A solute is the substance that dissolves in the solvent. - Common solutes that dissolve in water include salt and sugar.
30
What is a soluble solid?
- A soluble solid is a solid that can dissolve in a solvent. - For example, salt is soluble in water because it dissolves in water.
31
What is a solution?
- A solution is a liquid that forms when the solute fully dissolves in the solvent. - For example, sugar dissolves easily in water to form a sugar solution.
32
What is solubility?
The ability of a solute to dissolve in a given solvent at a given temperature.
33
What is a saturated solution?
A solution that cannot dissolve any more solute at a specific temperature.
34
What is an insoluble solid?
- A solid that does not dissolve in a solvent. - - For example, sand is insoluble because it does not dissolve in water.
35
What is a suspension?
A mixture that forms when a solid does not dissolve in a solvent.
36
What is a solubility curve?
- A curve drawn on a graph of solubility against temperature - It shows how the solubility of a solute changes with temperature
37
What can be interrupted from solubility curves?
- Solubility of a substance at a specific temperature - Trend in solubility for a given substance
38
What is the hardness in water caused by?
By the presence of calcium ions and magnesium ions. These ions dissolve into the water as it flows through soil and rocks after falling to the ground as rain.
39
What happens when soap is added to hard water?
The soap reacts with the ions to form ‘scum’, which is a white solid. This prevents the soap from creating a lather
40
What is the The ‘lather depth’ method?
1) Measure out a fixed volume of a water sample to a boiling tube. 2) Measure out a fixed volume of soap solution and add it to the water sample in the boiling tube. 3) Put a bung in the top of the boiling tube and shake the mixture vigorously for 5 seconds. 4) Measure the depth of the layer of lather that forms in the tube. 5) Repeat steps 1 – 4 for the other water samples. 6) Compare the lather depth for each sample. The sample with the smallest lather depth is the hardest sample of water.
41
What is the ‘soap volume’ method
1) Measure out a fixed volume of a water sample to a boiling tube. 2) Put a bung in the top of the boiling tube and shake the mixture vigorously for 5s 3) If a long-lasting lather forms, stop adding soap solution. 4) Record the volume of soap solution needed to form the long-lasting lather. 5) Repeat steps 1 – 5 for the other water samples. 6) Compare the soap solution, the sample with the largest soap solution volume is the hardest sample of water.
42
What health benefits do dissolved calcium compounds provide?
Strengthening teeth and bones, reducing heart disease
43
Why is it often desirable to remove hardness from water?

Hard water causes various problems
44
What is permanent hardness in water?
Hardness that cannot be removed by boiling
45
What are the methods to remove permanent hardness from water?
Addition of sodium carbonate Use of an ion exchange column
46
How does sodium carbonate remove hardness from water?
It reacts with calcium and magnesium ions
47
What is a disadvantage of using sodium carbonate to remove hardness?
It forms limescale that can block pipes
48
What is limescale made of?
Calcium carbonate and magnesium carbonate
49
What is the function of an ion exchange column?
It removes hardness from permanent hard water
50
How does the ion exchange process work in an ion exchange column?
Calcium/magnesium ions are replaced by sodium ions
51
What happens when sodium ions in the resin are depleted?
The resin can be regenerated with sodium chloride
52
Why are ion exchange columns considered expensive?

They require costly materials and maintenance
53
How can the cost of using an ion exchange column be reduced over time?
By regenerating the resin with sodium chloride
54
What are the advantages and disadvantages of using sodium carbonate and ion exchange columns for removing hardness?
Advantages of sodium carbonate: Cheap and easy to add Disadvantages of sodium carbonate: Forms limescale, causing blockages Advantages of ion exchange columns: Continuous process, reusable Disadvantages of ion exchange columns: Expensive to set up and maintain
55
What is temporary hardness?
A type of water hardness that can easily be removed by boiling the water.
56
What is formed when temporary hard water is boiled?
Limescale
57
What effect does limescale have on machinery that heats water?
It causes 'furring' and slows heating
58
How does limescale affect the efficiency of heating appliances?
It makes them less efficient by slowing heat transfer
59
What is a limitation of boiling water to remove temporary hardness?
It only works for small volumes of water
60
Can boiling water remove permanent hardness?
No, it cannot remove permanent hardness
61
What happens to temporary hard water samples when boiled?
They become soft
62
What do the results for permanent hard water samples indicate after boiling?
They will not change
63
What are the advantages of using hard water?
- Beneficial for heart health - Supports strong bone development in youth
64
What are the disadvantages of using hard water?
- Causes limescale in heating appliances Slows down heat transfer, reducing efficiency - Reacts with soap to form scum Requires more detergent for effective cleaning
C UNIT 1
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