Download Unit 2 National 4 Summary Sheet

Unit 2 National 4 Summary Sheet
What I should know or be able to do
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Fuels
A hydrocarbon fuel is substance which burns in oxygen to
release energy.
Chemical fuels have energy-rich chemical bonds created using
the energy from the Sun.
Energy is released when a fuel is burned (oxidised).
Combustion is the reaction of burning a fuel in oxygen.
Combustion is an example of an exothermic reaction.
This means heat is given out.
The fire triangle can explain how to
control fires.
Fossil fuels were formed from the decayed and fossilised
remains of plants and animals that lived millions of years ago.
Fossil fuels are mainly hydrocarbons with some impurities.
Sulfur is an impurity which burns to form sulfur dioxide.
This dissolves in rain water to produce acid rain.
Fossil fuels are a finite resource and will run out.
Alternative fuels e.g. hydrogen, biogas and methanol are being
developed.
Hydrogen burns to produce only water so it does not
contribute to greenhouse gases.
I can list the benefits and risks of different energy sources
and their impact on the carbon cycle.
I can describe the different uses of biomass as a fuel.
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What I should know or be able to do
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Hydrocarbons
Hydrocarbon molecules contain carbon and hydrogen only
Fractional distillation is the process used for separating crude oil
into fractions which have a given range of boiling points.
Small molecules have low boiling points and reach the top of the
tower.
The larger the molecule the higher its boiling point and the lower
down the tower it is collected.
I can describe the properties and uses of different fractions.
Hydrocarbons produce carbon dioxide and water when they
burn in a plentiful supply of oxygen.
Carbon dioxide is a greenhouse gas which contributes to global
warming.
Carbon dioxide emissions can be reduced using methods such
as carbon capture.
Hydrocarbons produce carbon monoxide, a poisonous gas, and
carbon when they burn in a limited supply of oxygen.
Catalytic converters reduce the output of carbon monoxide
from car exhausts.
When hydrocarbons burn mass is conserved – the mass of the
reactants equals the mass of the products.
The Alkanes are a group of hydrocarbons.
I can name and identify straight-chain alkanes from full
structural formulae and molecular formulae up to C8.
The Alkenes are another group of hydrocarbons.
Alkenes have a C=C double bond.
Alkenes are unsaturated molecules as they have a double bond
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Alkenes decolourise bromine solution
I can name and identify straight-chain alkenes from full
structural formulae and molecular formulae up to C8.
Cracking is a process used to make shorter chain alkanes and
alkenes.
What I should know or be able to do
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Consumer Products
Plants are a source of carbohydrates and oils which can be
used for food or fuel.
Carbohydrates are compounds which contain carbon, hydrogen
and oxygen.
In carbohydrates the hydrogen and oxygen atoms are in the
ratio of two to one.
Glucose is a simple carbohydrate with the formula C6H12O6.
Starch is a complex carbohydrate formed by joining many
glucose molecules.
I can describe the chemical test for glucose using Benedict’s
solution
(Benedict's turns from blue to orangey red)
I can describe the chemical test for starch using iodine
(Iodine turns from brown to blue-black)
Plants convert glucose into starch for storing energy.
Starch is broken down into glucose during digestion.
Glucose can pass through the gut wall into the bloodstream
because it is a small molecule.
Glucose is used in cells during respiration.
Enzymes present in yeast can convert glucose into ethanol.
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Ethanol is the alcohol in alcoholic drinks.
Fermentation is the process which converts carbohydrates
into ethanol.
Alcohols mix with water but do not alter the pH.
Different plants are used to produce different alcoholic beverages
e.g. grapes make wine, apples make cider and potatoes make vodka.
Fermentation can only produce alcohol solutions up to about
13%
Above this, the enzymes in the yeast stop working.
Distillation is carried out to get the higher concentrations of
ethanol in spirits. e.g. whisky, gin and vodka are all distilled.
The alcohol content of drinks is measured in units.
One unit of alcohol = half a pint of beer or a small glass of
wine.
The safe drinking level for men is 21 units per week and 14
units for women.
What I should know or be able to do
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Plants to Products
Plants are used to make everyday products such as
 clothing e.g. cotton for jeans, flax to make linen
 soaps e.g. tea tree oil, olive oil
 cosmetics e.g. henna for hair or skin dye
 dyes e.g. indigo is the blue dye used for jeans
 medicines e.g Aspirin from willow bark, arnica soothes
bruises
 foods e.g. bread from wheat
 food colourings e.g. blueberries (blue), beetroot (red)
I can describe how plants are used to make useful products.
Alcohols have many uses
 fuels
 solvents
 bactericides e.g. in alcohol hand gels
 feedstocks - used to make other chemicals e.g. esters
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