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Science Assessment Term 3 - Coggle Diagram
Science Assessment Term 3
3.1 Filtration and Evaporation
Filtration can separate an insoluble solute in a mixture. E.g. sand from water.
It uses filter paper, which allows water to pass through, but not sand.
This is because filter paper has tiny holes in it.
The water particles are smaller than the holes, so they pass through. In this case, the water is called the filtrate.
Meanwhile, the sand particles are bigger, so they get left behind. In this case, the sand is called the residue.
Evaporation can separate a soluble solute in a solution. Eg. salt from water.
Heat the mixture in a Bunsen burner until some of the water will evaporate quickly.
Then, leave the rest in a warm place. This will allow the water to evaporate slower and let the crystals become larger.
The slower the water evaporates, the longer the crystals will take to form, and the bigger they will be.
3.2 Neutralisation
When an acid and alkali react to make a salt and water.
The first part of the salt's name depends on the alkali, and the second part depends on the acid.
E.g. For Alkalis:
Sodium Hydroxide => Sodium ...
Copper Oxide => Copper ...
Calcium Oxide => Calcium ...
E.g. For Acids:
Hydrochloric Acid => ... Chloride
Sulfuric Acid => ... Sulfide
Nitric Acid => ... Nitrate
Butanoic Acid => ...Butanoate
Safety guidance for disposing acids:
Avoid contact with skin and eyes.
Wear eye protection and gloves.
Do not inhale the substance.
Do not empty into drains.
Must have the same amount of both acid and alkali.
The salt will be much less harmful than both the acid and alkali.
Acid pH : <7 Alkali pH : >7
Litmus paper:
Red: Acidic
Blue: Alkaline
3.3 Paper chromatography
Separates mixtures of dyes. E.g. pen ink
The water carries the dyes up the paper.
The more soluble/ paper resistant dyes will travel further up the paper.
The less soluble/ paper resistant dyes end up lower on the paper.
Paper = Stationary Phase
Water = Moblie Phase
If the ink is insoluble, it will stay on the base line
You can identify the dyes by calculating its Rf value.
distance travelled by the dye
Rf = ----------------------------------------
distance travelled by the solvent
As different substances have different Rf values, you can find out the substance matching the Rf value on a database.
DIFFERENT SOLVENTS HAVE DIFFERENT RF VALUES
Don't:
Let the ink touch the solvent, as the ink will then dissolve into the solvent
Draw the line in pen, as the pen ink will also travel up the paper
3.4 Gas Chromatography
Similar to Paper chromatography, but with gases.
Used to measure alcohol in blood.
The blood sample is heated, so any substances in the blood evaporates and goes into a gas chromatography instrument.
Helium is also added to the mixture of gases, which acts as the mobile phase, similar to water in paper chromatography.
The mixture flows through a polymer column, which is the stationary phase, similar to paper in paper chromatography.
Different substances move through the column at different speeds, which depends on how strongly it's attracted to the polymer.
Scientists interpret the gas chromatogram by seeing the spikes, indicating what substances the instrument detects.
3.5 The Reactivity Series
Shows how vigorously each metal reacts.
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
(Carbon)
Zinc
Iron
Lead
Copper
Silver
Gold
Platinum
Iron + Water + Oxygen ==> Hydrated Iron Oxide (Rust)
Because iron is near the bottom of the series, it reacts slowly.
Displacement Reactions happen when a more reactive substance removes a less reactive substance from its compound.
e.g. magnesium + copper sulfate ---> magnesium sulphate + copper
3.6 Biodegradable Materials
Biodegradability - The time it takes for it to be naturally broken down by bacteria or fungi.
Sisal is a natural, biodegradable material, obtained from plants. It's an insulator and does not catch fire easily. However, they are less comfortable and can be stained easily.
Wool is a natural, biodegradable material, obtained from sheep. Like sisal, it's an insulator and does not catch fire easily. It is also very soft. However, it is expensive and can be stained easily.
Polypropene is a synthetic polymer, made from substances found in crude oil. It is hard wearing and easy to clean.
Polypropene is not biodegradable, meaning it may remain unchanged for many years.