S1 SCI CHAP 4 SEPARATION TECHNIQUES Flashcards
Name every separation technique you have learned so far.
filtration, simple distillation, fractional distillation, sublimation, magnetic attraction, paper chromatography, separating funnel, crystallisation,evaporation to dryness.
State what filtration is and one application of it.
Filtration is used to separate a insoluble solid from the liquid in a solid-liquid mixture. Equipment such as kitchen sieve, filter paper. Filtrate, aka the liquid is collected as filtrate in a beaker while the insoluble bits are collected as residue in the filter paper.
Filtration makes use of filtering equipment (sieve, filter paper, filter funnel etc.).
One application: Tea strainers separate tea leaves from the tea.
State what simple distillation is and one application of it.
simple distillation is used to separate a pure solvent from a solution (soluble solid-liquid mixture). It uses the following equipment: Bunsen burner, boiling flask, thermometer, condenser, beaker, etc.
Simple distillation makes use of a tripod stand, wire gauze, thermometer, round-bottomed flask/boiling flask/distilling flask, condenser, and receiving/collection flask.
application: producing distilled water.
State what fractional distillation is and one application of it.
fract. distillation is used to separate a mixture of miscible liquids that have different boiling points.
Frac distillation makes use of a tripod stand, a boiling flask, glass/ceramic beads, a thermometer, a condenser, and the receiving flask.
This can be applied when making food flavourings.
State what magnetic attraction is and one application of it.
Magnetic attraction is used to separate magnetic materials from non-magnetic materials.
Magnetic attraction makes use of magnets.
It can be used for the salvaging of iron or steel.
State what sublimation is and give examples of substances that can sublimate.
sublimation is the process where a substance changes from a solid to a gas without passing thru the liquid state.
Sublimation makes use of a tripod stand, wire gauze, an evaporating dish, and a wet cloth (opt.).
Some substances that are able to sublimate are: Dry ice, iodine, chloride
State what paper chromatography is and one application of it.
Paper chromatography is used to separate small amounts of substances, esp pigments, from a mixture. This uses the different solubilities of the different substances.
Paper chromatography makes use of a test tube, a piece of chromatography paper, a pencil, water/ethanol, ruler, and a test tube stopper.
This can be used to determine whether a sample is pure. It can also be used to identify colours in dyes.
MORE SOLUBLE- TRAVELS UP FASTER AND COVERS MORE DISTANCE
IDENTICAL DYES- SAME DISTANCE + SAME HEIGHT WHERE DOT IS PLACED.
What is the separating funnel technique used for?
The separating funnel is used to separate an immiscible liquid-liquid mixture.
The separating funnel technique makes use of a separating funnel, beaker, and a retort stand.
Application: separating oil and water.
State what evaporation to dryness is and one application of it.
evaporation to dryness is used to separate and obtain a solute from a solvent. This is used in soluble solid-liquid mixtures.
One application: production of preserved food such as herbs and small fishes.
State what crystallisation is and its process.
crystallisation is used to obtain solids of a low melting point from a soluble solid-liquid mixture. As the solid is known to decompose over direct flame, crystallisation is used. The solution is heated for a while to make a saturated solution. It is then left to cool down to room temp. This is when crystals are formed. the cold solutions is then filtered to get the crystals. This can be used to obtain sugar crystals from a sugar solution.
crystallisation uses a tripod stand, wire gauze, and an evaporating dish.
State few substances that are magnetic and those that are non-magnetic.
magnetic- Cobalt, Iron, Nickel, Steel
non-magnetic- Gold, Silver, Aluminium
What are miscible and immiscible liquids? (+e.g.)
miscible: liquids that mix tgt completely to form a solution.
e.g. ethanol, water
immiscible: liquids that do not dissolve in each other.
e.g. oil and water.
why can’t a pen
be used to mark the line+dot on the chromatography paper?
The pen ink may be soluble in the solvent as well, and will separate as well.
Why must the dye spot be made as small as possible?
To prevent any spots from overlapping.
How can a pure substance be identified when using paper chromatography?
the sample used only produces one dot.
what is Rf, what is it used for, when is it used, and how do we calculate?
Rf- retention factor of a substance
Rf is the ratio between the distance travelled by the substance (solute) and the distance travelled by the solvent.
It is required to calculate Rf as we can compare the experimental Rf values with those of pure substances to detect components in a substance.
the numerator is the distance travelled by the solute, and the denominator is the distance travelled by the solvent.
dividing the two values gives us the Rf reading.
give 3 practices to reduce and reuse our water.
Reduce:
- Use half flush whenever possible.
- Wash vegetables in a container.
Recycle:
- Use water used to wash rice and vegetables to water plants
- reuse water frm the washing machine to flush toilets or wash the floor.
Explain reverse osmosis and give an example of when it is used.
Reverse osmosis removes dissolved salts, disease causing micro organisms, and other chemical molecules. It is similar to filtration. During reverse osmosis, the water is pumped at high pressures through PARTIALLY PERMEABLE MEMBRANES through very small pores such that only water molecules could pass through.
Reverse osmosis is used as a part of the treatment process in NEWater to remove viruses and other contaminants.
How does Sg use separation techniques to ensure a sustainable source of potable water.
NEWater- reverse osmosis, microfiltration (filtration), ultraviolet disinfection
Desalinated taps: Desalinated water- reverse osmosis or distillation
Treatment of water from a local catchment- filtration
Why is water important to us?
Water is essential for all living things to survive.
Water is required to cook wash, and clean
Water is required to take part in activities like swimming and canoeing.
Water is used in industries to fabricate products.
What is the purpose of the condenser in distillation?
To condense the gas into liquid to be able to collect it as distillate.
What is the purpose of the thermometer in distillation?
To measure the boiling point of the liquid in the distilling flask.
Why is the filter paper wet before using it?
to obtain more filtrate and to obtain it faster as the wet filter paper will not absorb the filtrate.
State two safety precautions.
Wear safety goggles, close the air hole before switching on the bunsen burner.
