Transcript Fuels Starter - Deans Community High School

Unit 2 Natures Chemistry
– Section 1
Carbon Compounds
Fuels Starter:
Qu. What do the following have in common?
• Oil
• Paraffin
• Coal
• Natural gas
• Wood
• Peat
Qu. What gas is used up every time we burn a
substance?
Fire and Fuels
Question: What things do we need to put together
to produce fire?
Copy the fire triangle into your notes.
Fuels
Definition:
A fuel is a substance that burns to produce heat
energy. Burning is also known as combustion.
Examples:
• Natural Gas
• Wood
• Oil
• Coal
• Peat
Energy Reactions
In a chemical reaction, energy can either be given
out or taken in! Complete the following:
Definitions:
1. Exothermic Reactions =
2. Endothermic Reactions =
When fuels burn this is an ______________
reaction because………..
Now read, complete and paste in 2.1a
Formation of oil and gas
1) Layers of
dead sea _____
settle on the
seabed.
2) Layers of
_____ and
rock build up on
top.
3) The heat and ________ from
these rocks over ________ of
years turns the creatures into oil
and gas.
Words – sand, millions, creatures, pressure
Formation of coal and peat
The formation of coal and peat also took
_________ of years but these ________
fuels are not made from sea creatures.
They were made from _________ and
plants in ancient swamps.
The coal and peat that we
have in West Lothian tells us
that millions of years ago
this area was just one big
swamp!
Words: fossil, trees, millions
Burning a Hydrocarbon Fuel
Think!
1.What two elements are in all
hydrocarbons?
2. How can you prove this?
Now paste in appendix and 2.1b and 2.1c
Distillation
Starter ;
1. What do we use distillation for?
2. Think – do you think bigger molecules
boil off first or last (Clue – do they have a
higher boiling point)
3. Read page 6 & 7 and answer qu1-3
Crude Oil
• Crude oil is a mixture of different hydrocarbons
called fractions.
• Crude oil is a source of many carbon based
products including fuels like petrol, diesel,
candle wax and lubricating oil as well as
different chemicals used to make many other
products
• These mixtures/fractions can be separated using
a process called Fractional Distillation
Fractional Distillation
To do:
1. Complete the true/false Fractional
distillation exercise
2. Fuels and Pollution
Create a spider diagram of ‘Fuels and
Pollution’ – fill it with as many pollution
issues associated with burning fuels.
(10mins)
Combustion – a Summary
•
•
•
•
A fuel is a substance that burns in O2 to produce energy
Combustion is another name for burning
Oxygen gas is needed for burning to take place
A reaction which gives out energy is called an EXOTHERMIC
reaction
• All combustion reactions (burning) are exothermic
• Most fuels are made from compounds containing carbon and
hydrogen (Hydrocarbons)
• Two types of Combustion – complete and incomplete
• Examples of fuels are petrol, coal, natural gas (methane), wood,
kerosene, paraffin and diesel – what are these used for?
• By blowing on a fire we increase the oxygen concentration – so it
burns with a hotter flame!
Now answer Qu1-8 on page 2 and complete appendix 2.1a
Research Task: Alternative Fuels
We know that petrol and diesel are fuels that are burned to produce energy.
Qu. What is the global environmental problem
associated with burning fossil fuels like petrol and diesel?
Qu. What will eventually happen to these fossil fuels?
So what will we use to produce the energy we need to power our cars,
heat our homes, supply us with electricity??
– can you suggest any alternatives?
Research Task: Using available textbooks or the internet research the
following 3 alternative fuels; ethanol, hydrogen and biogas.
Success criteria; You must write about each alternative fuel detailing
i)how it is made
ii) where it is used
iii) advantages and disadvantages both in terms of being a fuel and
the environment
What are Hydrocarbons?
• A hydrocarbon is a molecule which
contains only the elements Carbon and
Hydrogen.
• Hydrocarbons are obtained from the
Fractional Distillation of crude oil.
• We use them for fuels in cars (octane) and
in cookers (methane).
• Hydrocarbons exist as different ‘families’
Hydrocarbons – Homologous Series
• Definition:Homologous
Series
– a group of chemically similar compounds which can
be represented by a general formula.
– Physical properties change gradually through the
series
Now paste in
handout and
turn to page 12
of booklet.
Hydrocarbons
We will focus on the following homologous
series;
• Alkanes (Straight and branched chains)
• Alkenes
• Cycloalkanes
Alkanes
Alkanes are SATURATED HYDROCARBONS.
HYDROCARBONS are molecules that are made up of only
_________ and _________ atoms. They share a general
formula. Which is…………..
SATURATED means that all of the carbon atoms are held
together by ________ bonds, for example:
Ethane
Butane
Alkanes are quite unreactive (but they do burn well to make
__________ __________ and ______).
Starter
1. What is a homologous series?
2. Which of the following are hydrocarbons?
A.
B.
C.
D.
E.
F.
Aim: To learn about the first 8 alkanes; their formula,
structures, properties and general formula.
How Do We group all these alkanes together?
See page 9 of data-booklet
Alkanes
» Methane
» Ethane
» Propane
» Butane
» Pentane
» Hexane
» Heptane
» Octane
» Nonane
» Decane
Monsters
Eat
Pupils
But
Prefer
Hairy
Haggis
or
Nice
Dinners
Structures: Alkanes – Methane
Build methane using the moly mods
• 3D Full Structural  2D Full Structural
Formula
Formula
Remember - Alkanes
• The Alkanes are a family of hydrocarbons
and all share the same chemical
properties:
– Single Carbon to carbon bonds ( - C – C - )
– All end in -‘ane’
– Saturated hydrocarbons
– All share a General Formula
Now paste in appendix 2.2 and 2.2a
Alkanes
• Each member can be represented in three
different ways:
Methane
Propane
• Full Structural
Formula
• Shortened Structural
Formula
• Molecular Formula
Alkanes
Alkane
(Carbon
Atoms)
Full
Structural
Formula
Molecular
Formula
Shortened
Structural
Formula
Methane
(1)
Ethane
(2)
Propane
(3)
Boiling
Point
-164
C2H6
CH3- CH3
- 89
Alkanes
Alkane
(Carbon
Atoms)
Butane
(4)
Pentane
(5)
Hexane
(6)
Full
Structural
Formula
Molecular
Formula
Shortened
Structural
Formula
Boiling
Point
Alkanes
Alkane
(Carbon
Atoms)
Heptane
(7)
Octane
(8)
Molecular Shortened
Formula
Structural
Formula
Full
Structural
Formula
Boiling
Point
Alkanes
Alkane
(Carbon
Atoms)
Molecular Shortened
Formula
Structural
Formula
Full
Structural
Formula
Boiling
Point
Methane
(1)
CH4
CH4
-164
Ethane
(2)
C2H6
CH3- CH3
- 89
Propane
(3)
C3H8
CH3- CH2- CH3
- 42
Alkanes
Alkane
(Carbon
Atoms)
Shortened
Structural
Formula
Boiling
Point
C4H10
CH3-CH2-CH2-CH3
-1
Pentane
(5)
C5H12
CH3- CH2- CH2- CH2- CH3
36
Hexane
(6)
C6H14
CH3-CH2-CH2-CH2-CH2-CH3
69
Butane
Full Structural Mole
Formula
cular
Form
ula
(4)
Alkanes
Alkane
(Carbon
Atoms)
Molecular Shortened
Formula
Structural
Formula
Full
Structural
Formula
Boiling
Point
Heptane
(7)
C7H16
CH3CH2CH2CH2
CH2CH2CH3
98
Octane
(8)
C8H18
CH3CH2CH2CH2
CH2CH2CH3
126
Alkanes General formula
The following hydrocarbons are members of a different
homologous series;
•
For every carbon there is 2 x hydrogen minus 2 (e.g. ethyne = 2
carbons and 2 hydrogens, butyne is 4 carbons and 6 hydrogens)
Their general formula is CnH2n-2
Using this as a guide – work out the general fromula for the alkanes.
The number of Hydrogen atoms = 2 times the number
of Carbon atoms
plus 2
General Formula for alkanes is CnH2n+2
Properties of Alkanes
• Alkanes have single carbon to carbon
bonds. This makes them saturated.
• The general formula for alkanes is;
CnH2n+2
• The boiling points of alkanes increase as
they get bigger
Energy from Fuels
• A fuel is a substance that burns in oxygen
to produce energy.
• Different types of fuels provide different
quantities of energy.
• We can measure the energy produced by
a fuel when it burns experimentally.
Measuring the Energy from Fuels
Alcohols can be burned to produce energy and are
regularly used in combination with other fuels to produce
energy.
E.g. In Brazil alcohols can be mixed with
petrol and be used in cars!
Experiment: Calculating the Energy Released from Fuels.
The combustion of alcohols is exothermic and in this
experiment the energy released from burning a known
mass of alcohol is used to heat a known amount of water.
From measurements taken, the quantity of energy
transferred to the water can be calculated.
Now collect and paste in the Experiment handouts.
Outcome 1: Fuels Investigation
General Aim: Investigate how the number of carbon atoms
in a fuel affect the energy it will produce.
Using the equipment and chemicals listed on the
sheet;
Plan in your groups a fair investigation method to
determine how varying the number of carbons in an alcohol
affect the energy released per gram of fuel.
(Remember to identify what you will change each time(your
independent variable) and what you will measure each time
(your dependent variable)
Check you plan with your teacher.
Variables in Investigations
• An independent variable is the factor you
change in each experiment in an investigation
• All other variables should be kept the same
• A dependent variable is the variable being
tested/measured in a scientific experiment.
Note:
The dependent variable is 'dependent' on the
independent variable. As the experimenter
changes the independent variable, the change in
the dependent variable is observed and recorded.
Today’s Planning
Aim:
Apparatus
Safety
Variables
Method – Use of equipment
- measurements to be taken
- repeated for alcohol
- repeated for different alcohols
Later: Results – Table of measurements and
sample calculation for converting to 1g
Now carry out your investigation and then write it up formally (on A4
paper) including the headings;
(You must write this up yourself not in a group)
1. Aim
2. The independent variable (what you changed),
3. The dependent variable (what you measured),
4. Safety
5. The method with a diagram, mentioning all the
equipment used and measurements
6. A table (with headings) of your measurements,
sample calculation, and table and graph of your
results (average energy)
7. Your conclusion (what you found out – must mention
results and link to the aim)
8. An evaluation (Comment on how well you felt exp. Went
and how you can improve your investigation)
Alkenes
• The Alkenes are a family of hydrocarbons
and all share the same chemical
properties:
– They contain a double Carbon to carbon
bonds ( - C = C - )
– All end in -‘ene’
– Are unsaturated hydrocarbons (due to c=c
double bond)
– All share a General Formula
Now paste in appendix 2.3 and 2.3a
Alkenes
Ethane
Ethene
Butane
Butene
A double bond means that alkenes can join with other
molecules. This make them REACTIVE. We can tell the
difference between alkenes and alkanes because alkenes
decolourise bromine water but alkanes don’t.
ALKENES
ALKANES
Alkenes are different to alkanes; they are unsaturated.
This means that they contain a _______ bond between carbon
atoms.
Homologous series
A homologous series is a family of chemicals that have
have the same general formula.
The alkanes are a
homologous series
because all members
have the same
_________ formula.
The alkenes are a
homologous series
because all members
have the same
__________ formula.
The first part of the name of a hydrocarbon depends
on the number of carbon atoms:
meth = ___, eth= ___, ____ = 3, _____ = 4, pent = ___,
____ = ____, ____ = ____, ____= ____.
Complete #1
The name for the alkane with 5 carbon atoms is ______.
The name for the alkene with 5 carbon atoms is ______.
The name for the alkene with 3 carbon atoms is
________.
The name for the alkene with 12 hydrogen atoms is
________.
The name for the alkane with 18 hydrogen atoms is
________.
Complete #2
The molecular formula for propane is ______.
The molecular formula for hexane is ______.
The molecular formula for butane is ______.
The molecular formula for ethene is ______.
The molecular formula for octene is ______.
The molecular formula for _______ is C4H8.
The molecular formula for _______ is C7H16.
The molecular formula for _______ is C6H12.
The molecular formula for _______ is C5H12.
The molecular formula for _______ is C2H6.
Cycloalkanes
Naming Hyrocarbons
Isomers
Turn to page 21 of booklet;
1. Starter: What is the definition of an
isomer? Are the two compounds on the
whiteboard isomers?
2. Collect and read appendix 2.6 – insert
them into notes.
3. Collect a set of molymods.
Now use the molymods to complete activity
2.15(a) and 2,15(c) - name all the isomers.
Alkanols (Alcohols)
Definition:
• The alkanol family (sometimes known as alcohols) is a
group of carbon compounds which contain an –OH
(hydroxyl) group. When attached to the molecule this is
known as a functional group.
• The alkanol ethanol, is used in drinks. However, many
(alkanols) alcohols are used as fuels.
• The name of all alkanols is very similar to the alkanes,
as are their structures:
E.g. Methanol:
E.g. Butan-1-ol:
Now turn to page 22
Copy and complete;
Alkanols
The Alkanols
Molecular Shortened
Formula
Structural
Formula
Methanol
CH3 OH
CH3 - OH
Ethanol
C2H5OH
CH3- CH2 - OH
Propanol
Butanol
CH3- CH2- CH2 -OH
Full Structural
Formula
Naming Alkanols & Isomers
• Just like the alkenes, the alkanols have isomers that are
dependent on the position of the functional group, in this
case the hydroxyl group (-OH).
Example;
and
Draw and name the structure below!
Now complete exercise 2.3
Move onto textbook – list some uses of alkanols.
Researching Alkanols
Using the internet find out about and write
a short report on;
• The chemistry of how alkanols (alcohols)
are made)
• The different uses of alkanols (alcohols)
http://www.chemguide.co.uk/organicprops/al
cohols/uses.html
Uses of Alcohols
• Drinks – the alcohol in beers and spirits is
ethanol.
• As a fuel – ethanol can be mixed with
petrol (Gasohol)
• Methylated spirits – industrial alcohol
• As a solvent – in perfumes and cosmetics
Carboxylic (Alkanoic) Acids
Carboxylic acids, sometimes known as
alkanoic acids, are a homologous group of
organic acids which contain the carboxyl
functional group:
• The third member is;
propanoic acid
• What do you think the name of the first and second
members are?
Copy and complete;
Carboxylic
Acids
The Carboxylic Acids
Molecular Shortened
Formula
Structural
Formula
Methanoic
acid
HCOOH
Ethanoic
acid
CH3 COOH
Propan__
acid
Butan___
acid
HCH3- -
CH3- CH2-
Full Structural
Formula
Uses of Carboxylic Acids
• Vinegar is a solution of ethanoic acid.
• Ethanoic acid can also be used as a preservative in the
food industry.
• Carboxylic acids are used in household cleaning
products including soap
• In manufacture of important organic compounds), acetic
anhydride (used in aspirins), cellulose acetate (used in
synthetic fibres), various dyes, perfumes & medicines.
• As a solvent it dissolves phosphorus, sulphur & iodine.
• Carboxylic acids can be used to make chemicals called
esters.
Researching Carboxylic Acids
Using the internet find out about and write
a short report on;
The different uses of carboxylic acids
(alkanoic acids)
• http://www.preservearticles.com/20110102
2309/uses-of-carboxylic-acids.html
Esters
Esters are made by reacting a carboxylic acid with an alcohol.
Making an Ester
Esters are made by reacting a carboxylic acid with an alcohol. This is known as
esterification and is a CONDENSATION reaction.
The name of the ester comes from the alcohol and carboxylic acid!
Ethanoic Acid
H
O
H-C - C
H
+ Ethanol
O-H
Ethyl ethanoate
CH3COOC2H5
H H
H O-C-C-H
H H
+
Water
H2O
Questions:
1. What is the name of the ester made by
combining ethanol and propanoic acid?
2. What is the name of the alcohol and
carboxylic acid which made the follow ester –
Butyl propanoate
Now paste in and read Appendix 2.13
Making and naming esters
Drawing and Naming Esters
In your groups;
1. Collect an ester.
2. Write down the alcohol and acid that
made it.
3. Now draw the ester.
4. Now smell the ester and complete the
table on page 2
Most esters have a pleasant odour and are used as perfumes and flavourings in
food.
Depending on the alcohol and acid used, many different fragrances can be
made.
ALCOHOL
ACID
pentanol
butanoic
acid
apricot
pentanol
ethanoic
acid
banana
Ethanol
butanoic
acid
apple
ethanol
ethanoic
acid
fruity
Name of Ester
ESTER
FRAGRANCE