Separating Mixtures And Water Treatment Flashcards
What does soluble mean?
A substance that will dissolves in fluid to form a solution
What does insoluble mean?
A substance that will not dissolve in a solvent (even after mixing)
What is a solute?
A substance that has dissolved in a solution (usually a solid)
What is a solvent?
A substance that dissolves a solute (usually liquid)
What is filtration?
Filtration separates an insoluble solid from a liquid
How does filtration work?
The liquid filtrate passes through the filter paper and the undissolved solid residue stays on the paper
What is decantation?
Decantation is another way of separating a liquid from an undissolved solid
How does decantation work?
A liquid is poured very slowly leaving the solid behind
What is evaporation?
Evaporation is used to separate a soluble solid from a solution
How does evaporation work?
The solution is heated as the solvent evaporates leaving the solid solute behind
What is crystallisation?
Crystallisation is another way is separating a soluble solid from a solution
- it is often used when making crystals from a solution where the solvent is water
How does crystallisation work?
By heating the mixture then putting the solution in a warm place to slowly let the solvent evaporate leaving saturated crystals (from the solute) to form
Describe the crystals produced from crystallisation
-hydrated
-containing water in their structure
-if strongly heated the water would evaporate away leaving anhydrous power (a substance is anhydrous if it contains no water)
Describe copper sulfate:
-blue
-copper gives it its crystal structure
What is distillation?
the process of separating a solvent from a solution
What is a condenser?
An apparatus used to condense gas (turning it into liquid) by cooling it down
At what temperature does water distil off?
100 degrees Celsius
What do anti-bumping granules do ?
Prevent the formation of large gas bubbles that cause violent boiling
Apart from a condenser , what other piece of equipment can you use to apply distillation?
A delivery tube
(With ice cold water in a beaker)
What is pure water?
-Water without impurities
-Water that is 100% water and contains nothing else
What is a test to prove that a solution is pure water?
-it will boil at 100 degrees Celsius
-it will freeze at 0 degrees
What is are miscible liquids?
Two liquids that mix
(Eg alcohol and water)
How are miscible liquids separated?
Using fractional distillation
How does fractional distillation work?
It uses a FRACTIONATING COLUMN allowing the separation of liquids that have boiling points that are different but are still quite close together
-The substance with the HIGHER boiling point condenses falling into the flask
-The substance with the LOWER boiling point emerges from the top
What are immiscible liquids?
Liquids that do not mix and form separate layers
Examples of miscible liquids:
-ethanol(alcohol) and water
-petrol and diesel from crude oil
Example of immiscible liquid:
Oil and water
How are immiscible liquids separated?
Using a SEPARATING FUNNEL
-The liquid with a LOWER density stays at the top (e.g oil)
-The liquid with a HIGHER density stays at the bottom (e.g water)
Example of decanting and filtration:
Sand and water
Example of evaporation:
Salt from salt solution
Examples of distillation:
-water from salt solution
-alcohol from sugar dissolved in alcohol
What is chromatography?
A method for separating several solids that are all soluble in the same solvent
What can be separated using chromatography?
- Dyes
- Inks
How does chromatography work?
- Dyes are placed at the bottom of the chromatography paper
- This is then placed in a SOLVENT (e.g water)
- As the water is drawn up the paper it moves different dyes at different rates depending on their SOLUBILITY in water
How do you know which dyes are more soluble?
- dyes which are MORE soluble in water move more QUICKLY up the paper
- dyes which are LESS soluble in water move SLOWLY up the paper
What is the solvent and paper referred as?
Paper - stationary phase
solvent - mobile phase
How do you work out the Rf value?
Rf = distance moved by pigment (measure centre of the spot)
——————————————————————————
distance from pigment to solvent front
- RF VALUES ARE USED TO IDENTIFY SUBSTANCES
-THEY MUST BE LESS THAN 1 AND WRITTEN AS A DECIMAL
Why is the 1cm line drawn in pencil?
-Because graphite is insoluble
-because the ink from pen would separate from the paper and mess up the experiment
Why are the spots labelled at the start?
Because they become unrecognisable after they separate
Why MUST the water level be below the spots?
So that the ink doesn’t dissolve into the water
What does the chromatography tell you about the pens?
Most inks are made up of two or more colours
What is water suitable for drinking called?
Potable
What is water treatment?
The process of making water safe to drink
What does water treatment do?
-removes insoluble/dissolved solids from the water
-kills harmful bacteria
What are the 3 main processes used to mark water clean enough to drink?
-sedimentation
-filtration
-sterilisation
How does sedimentation work?
-Water is put in a tank where the water is very still
-particles of undissolved solid sink to the bottom of the tank where they settle
-water is removed from higher up the tank which now contains less solid
What are coagulants?
Chemicals that are sometimes added to help particles of solid to stick together to make larger lumps of sediment
How does filtration work?
-Water is passed through a series of sand filters
-The sand filters removes particles of insoluble/dissolved solid
How does sterilisation work?
Chlorine is added to the water supply to kill bacteria/microbes
(ANOTHER GAS CALLED OZONE CAN ALSO BE USED TO STERILISE WATER INSTEAD OF CHLORINE)
What is ground water?
Water in underground streams and rocks
What is fresh water?
Water in underground:
-streams
-rocks
-rivers
-lakes
-ice caps
-glaciers
What is waste water?
Water used from homes , industry , and agriculture
How can sea water be made potable?
-Distillation
-Reverse osmosis
Why is sea water not able to become potable with water treatment?
Because it contains too many dissolved substances (salt) that cannot be removed by filtration
What is the process used to make sea water drinkable called?
Desalination
What makes distillation so costly?
-the evaporation of the water
-it uses too much energy
What is reverse osmosis?
-water is pumped through a semi-permeable membrane (A TINY SIEVE WITH HOLES) that lets through comparatively small water molecules but not the much larger ions of the dissolved substances
What is chlorine?
A poisonous gas that is used to kill microbes in water
What is the test for chlorine?
Blue litmus paper turns red and is bleached white
If chlorine is poisonous then why is it used in swimming pools and in treating drinking water?
-because it is used in small amounts
-because it’s not in a gas form
