Chapter 4: Exploring Diversity of Matter Using Separation Techniques Flashcards
How does the flamingo feed itself?
By putting its head upside down into the water and moving its head from side to side underwater.
What is the use of the flamingo’s large tongue?
As a pump to suck in water containing food particles. The flamingo’s tongue then squeezes out water from its beak.
What happens when water is squeezed out through the flamingo’s beak?
Food particles in the water are trapped by comb-like structures lining the beak.
What does the flamingo depend on to get its food?
The flamingo depends on the separation of food particles from the water to get its food.
What are separation techniques used for?
To separate mixtures.
Name some mixtures that are separated with the use of separation techniques.
- Magnetic and non-magnetic materials
- Liquid and insoluble solid (suspension)
- Liquid and soluble solid (solution)
- Small quantity of substances that are dissolved in a solvent.
What are the different types of separation techniques that I must know?
- Magnetic attraction
- Filtration
- Evaporation
- Distillation
- Paper Chromatography
- Microfiltration
- Reverse Osmosis
How are magnetic and non-magnetic materials separated?
By the use of magnetic attraction, in:
- salvaging of iron and steel
- food processing
How are liquid and insoluble (i.e. cannot be dissolved) solid (suspension) separated?
By filtration, in:
- coffee makers
- water treatment
How are liquid and soluble solid (solution) separated?
By:
- Evaporation, in for instance, salt production;
- Distillation, in for instance, desalination of seawater.
What is the purpose of desalination?
To obtain drinking water.
How are small quantities of substances that are dissolved in a solvent separated?
By paper chromatography, in for instance, finding out the dyes used in ink or food.
What are micro filtration and reverse osmosis used in?
Purification of treated used water.
What is the purpose of purifying treated used water through the use of micro filtration and reverse osmosis?
To obtain drinking water.
What is one of the most popular drinks in the world?
Tea.
How is the traditional tea made?
By mixing dried tea leaves with hot water. The flavour of the tea leaves will dissolve into the water. The mixture of tea leaves and water is then poured over a sieve to separate the tea leaves from the water before the tea is served.
Why is the sieve able to separate the tea leaves from the drink?
Because the tiny holes in the sieve allow the water to pass through, while the tea leaves are trapped.
How is the preparation of tea drinks made simpler nowadays?
Through the use of tea bags.
What is a tea sieve used as?
A simple filter to separate the tea leaves from the tea.
Give some examples of the many mixtures that are around us.
Air, sea water and crude oil.
Can mixtures contain useful substances?
Yes.
How can we make use of the useful substances that are found in mixtures?
By separating these mixtures of substances with the use of physical separation techniques.
Do these physical separation techniques produce any new substances in addition to obtaining the original substances?
No. Chemical reactions are not involved.
Can a combination of two or more techniques be used / needed to separate a mixture sometimes?
Yes.
How many separation techniques must I be familiar with?
5
What is the selection criteria for the separation technique to be use? or
How does one decide on the separation technique to be used?
The technique used to separate a mixture depends on:
- the physical properties of the substances in the mixture; and
- the substances to be obtained from the mixture.
What fact is the use of magnetic attraction based on?
Magnetic attraction makes use of the fact that only some materials are attracted to magnets.
What is magnetic attraction used for?
To separate magnetic materials from non-magnetic materials, e.g. separating a mixture of sand and iron fillings.
What are the advantages / benefits of using magnetic attraction to separate magnetic and non-magnetic materials?
- The separation of magnetic and non-magnetic materials is:
- quicker; and
- more efficient in many industries.
Name some industrial applications of magnetic attraction.
- Salvaging of iron and steel
2. Food processing
Are iron and steel magnetic materials?
Yes
Where can iron and steel be recovered from?
Junkyards
Why are iron and steel recovered from the junkyard?
So that these metals can be recycled.
What is the advantage / benefit of recycling iron?
Recycling iron prevents iron from being used up as metals are limited natural resources, i.e. prevents the depletion of natural resources.
How are iron and steel separated from other materials in the junkyard?
Through the use of a powerful magnet. When the magnet is turned off, iron and shell are dropped into a collection bin.
What happens to the iron and steel that are retrieved from the junkyard by the powerful magnet?
The iron and steel are sold as scrap metal and brought to recycling centres.
What happens to these recycled iron and steel?
They are reused in new objects that are made.
What is the advantage / benefit of using magnetic attraction in food processing?
The magnets used can remove harmful objects from food.
Why is magnetic attraction used in food processing?
During food processing, metal pieces may accidentally get into the food products.
Why is food placed in magnetic separators?
To detect and remove any metal pieces in the food.
Why is it necessary to ensure that metal pieces are removed from food?
To keep the food clean and safe to be eaten.
What happens to the food after the metal pieces (if any) are removed?
The food is further processed before being sold in shops.
What fact is the use of the filtration method based on?
Filtration makes use of the fact that, in a suspension, insoluble solids are of a larger size than liquid particles.
What is the filtration method used for?
To separate insoluble solids from a suspension.
What is filtration?
Filtration is a technique used to separate an insoluble solid from the liquid in a liquid-solid mixture.
How do our kidneys remove waste?
Through filtration.
How many times is our blood filtered everyday?
20 - 25 times every day.
What are the large insoluble particles (solids) called? or
What are the trapped solid particles that remain on the filter paper called?
Residue.
What does the filter paper do to the residue?
Trap the residues / insoluble particles.
What can be found in filter papers?
Tiny pores.
Why does the filter paper have tiny pores?
In order to allow the smaller liquid particles to pass through while trapping the larger solid particles.
What is the liquid that passes through the filter paper called?
Filtrate
What equipment do we need to carry out a filtration experiment?
glass rod filter paper filter funnel beakers stand See Pg 69, textbook
What is filtration not used for?
To separate the components of a solution, as the solute is soluble in the solvent and other liquids. The solution would be able to pass through the pores in the filter.
Name some applications of filtration in our everyday lives and in the industrial world.
- Coffee makers… use of filter jugs to prepare fresh coffee.
- Water treatment… water from Singapore’s reservoirs is purified before it can be used for drinking. Part of the filtration process involves filtration, a cost-saving technique for producing potable water compared to other methods.
- Nose hairs in our nostrils help to filter the air entering our lungs.
- Our kidneys function as a filter for our blood.
What are the filter jugs found in coffee makers used for?
To prepare fresh coffee.
List the coffee maker’s filtration steps of making fresh coffee.
- Filter paper is placed in the filter cone.
- Ground coffee is poured into the filter paper.
- Water is poured into the filter cone.
- The filter paper separates the ground coffee from the liquid coffee.
See Page 70 of textbook.
Do the waters from our reservoirs need to be purified before they can be used for drinking>
Yes.
What is the advantage / benefit of using the filtration method to purify our reservoir water so that they can be used for drinking?
It is a cost-saving technique for producing potable water as compared to other separation techniques / methods.
How is Singapore’s water supply improved?
By adding the chemical sodium silicofluoride to our water supply (since 1957). This is a requirement by the Ministry of Health to prevent tooth decay.
Why is the chemical sodium silicofluoride added to Singapore’s water supply?
To help prevent tooth decay.
Is it necessary / mandatory / compulsory to add sodium silicofluoride into Singapore’s water supply?
Yes. It is a requirement by the Ministry of Health
List the steps of using filtration in water treatment.
- Raw water from the reservoir is treated with chemicals to kill germs and bacteria.
- Water is filtered through layers of sand beds, which contain sand grains of different sizes (fine sand, gravel and pebbles).
- Solid silt and sand particles are removed from the water.
- Clear water then flows out.
Name some parts of our body which also use filtration to control the types of substances entering and leaving our body.
- Nose hairs in our nostrils help to filter the air entering our lungs.
- Our kidneys function as a filter for our blood.
What is evaporation?
Evaporation is the technique used to separate dissolved solids from a solid-liquid mixture.
What fact does the evaporation technique make use of?
Evaporation makes use of the fact that the solvent in a solution can vaporize at any temperature, leaving behind a residue of the solid that was dissolved in the liquid.
List the steps of separating dissolved solid from a solid-liquid mixture using evaporation.
- A solution (e.g. sugar solution) is heated over a water bath.
- When the solvent has completely evaporated, no liquid is left behind.
- The solid left behind is the residue.
(See figure 4.8 in Page 72 of textbook)
(See also think and explore section in Page 72 of textbook.)
Why is it important to heat the solution gently over a water bath?
This is because direct heating is very vigorous and may cause the solid inside the evaporating dish to sputter out.
How is salt obtained?
Through the evaporation of seawater.
What is common salt used for?
As a food preservative or as a seasoning in dishes.
How is salt obtained in some parts of the world where temperatures are high?
By allowing the seawater to flow into large flat pans called salt pans. The heat from the sun evaporates the water, leaving the salt behind. The salt is then piled into heaps to dry.
(See Page 73 of textbook.)
How may potable water be obtained from a ground water mixture?
Through the use of distillation.
How does the distillation technique work?
See Figure 4.10 in Page 74 of textbook
Water from the ground evaporates as water vapour. The water vapor formed comes into contact with the cool underside of the plastic sheet and condenses on the plastic sheet. The condensed water collects in the cup.
What are the two main processes involved in distillation?
Vaporisation and condensation.
Is distilled water clean and safe for drinking?
Yes.
How can pure water be obtained from a ground water mixture?
Through distillation. A pure liquid can be obtained from a solid-liquid or a liquid-liquid mixture through distillation.
How may distillation be carried out using laboratory apparatus?
- The mixture (e.g. salt solution) is heated in a distilling flask until the mixture boils.
- The vapour formed is allowed to escape into the condenser where the vapour condenses.
- The pure liquid collected from distillation is called the distillate. This distillate is collected in a conical flask.
See Figure 4.11 in Page 74 of textbook.)
What is the pure liquid collected from distillation called?
Distillate
Give some examples of how distillation is used.
- To separate pure water from a solution of mineral salts and water.
- Treatment of seawater to obtain potable water.
What fact does paper chromatography make use of?
Paper chromatography makes use of the fact that different substances in a mixture dissolve to different extents in a particular solvent. This means that the substances move at different rates up the chromatography paper.
Which substances move faster up the paper chromatography?
Substances that are more soluble in a solvent will move faster than substances that are less soluble.
What is chromatography?
It is the technique used to separate small amounts of substances from mixtures based on the different solubilities of the components in a particular solvent.
What is the advantage of using separation methods such as filtration and distillation?
A large amount of the mixture can be separated.
What is the advantage of using paper chromatography as a separation method?
Convenience. It is more convenient to use paper chromatography when working with a small amount of mixture.
List the steps of separating small amounts of substances from mixtures using chromatography.
- A spot of ink is applied to a piece of chromatography paper which is then lowered into the solvent. The solvent dissolves the dyes in the ink. The dyes move up the paper together with the solvent.
- The different dyes in the ink mixture travel at different rates along the paper.
- At the end of the experiment, the different dyes in the ink will be separated on the chromatography paper. The paper with the different colored spots is called a chromatogram.
See Fig. 4.12 in Page 75 of textbook.
What can paper chromatography be used for?
- To identify the contents of a mixture.
- To test the purity of a substance.
- To identify food colouring.
- To identify the dyes used in ink.
What are food colourings often used in?
In candies, cakes and soft drinks to make them look more appealing.
Why are food colourings often used in candies, cakes and soft drinks?
To make them look more appealing.
Are there certain food colourings that are harmful to our body?
Yes.
What can paper chromatography be used for?
It can be used to ensure that harmful food colourings are not used in food.
What is ink usually a mixture of?
Different types of dyes.
What can paper chromatography be used to find?
The different types / kinds of dyes that make up different inks.
What is paper chromatography especially useful for?
It is especially useful in cases where we need to find out if written documents have been forged.
Can the dyes that make up pen ink be separated?
Yes. Through the use of paper chromatography.
