Transcript Chemistry 1 HT Warm up - Thomas Tallis Science

Chemistry 1
HT
Warm up
Atomic
structure
Atomic structure
In an atom the number of electrons is equal to the
number of protons in the nucleus
Atomic mass and atomic number
Mass Number =
Number of protons + Number of neutrons
Atomic Number =
Number of protons
Number of electrons
9
4
Be
Beryllium has:
4 protons
4 electrons
How many neutrons?
Electronic structure
1st shell holds a maximum of
2 electrons
2nd shell holds a maximum
of 8 electrons
3rd shell holds a
maximum of 8 electrons
• Each level/shell has a maximum number of electrons it can hold
• Electrons will fill the levels nearer to the nucleus first
Bonding
How does electron structure affect reactivity?
The reactivity of alkali metals increases going down the group. What is the
reason for this?
increase in reactivity
Li
Na
 The atoms of each element get larger going
down the group.
 This means that the outer shell electron gets
further away from the nucleus and is shielded by
more electron shells.
 The further an electron is from the positive
nucleus, the easier it can be lost in reactions.
K
 This is why the reactivity of the alkali metals
increases going down group 1.
Ionic and covalent bonding
• When elements react, their atoms join with other atoms to
form molecules and/or compounds. This is Bonding.
• Bonding involves giving, taking or sharing electrons to form
ions or molecules
Conservation of mass
No atoms are lost or made during a chemical
reaction so the mass of products equals the
mass of the reactants
Limestone
Limestone cycle
Pros and cons of quarrying
Extracting
metals
How does reactivity affect extraction?
increasing reactivity
The reactivity of a metal determines how it is extracted.
potassium
sodium
calcium
magnesium
aluminium
(carbon)
zinc
iron
lead
(hydrogen)
copper
silver
gold
platinum
Metals above carbon in the
reactivity series must be
extracted using electrolysis.
Electrolysis can also be used
to purify copper.
Metals less reactive than
carbon can be extracted from
their ores by reduction using
carbon, coke or charcoal.
Platinum, gold, silver and
copper can occur native
and do not need to be
extracted.
Electrolysis of copper salts
Copper can be obtained from solutions of copper salts by
electrolysis or by displacement using scrap iron
Alloys can be designed to have properties for
specific uses
Stainless steel
Low carbon steel
High carbon steel
Low carbon steels are easily shaped, high carbon steels are
hard and stainless steels are resistant to corrosion
Hydrocarbons
Hydrocarbons
• Most of the compounds in crude oil consist of
molecules made up of hydrogen and carbon atoms
only (hydrocarbons)
Alkanes
• Most of these are saturated hydrocarbons called
alkanes which have the general formula CnH2n+2
Fractional distillation
• The many hydrocarbons in crude oil maybe separated into fractions by
evaporating the oil and allowing it to condense at a number of different
temperatures.
• Each fraction contains molecules with similar number of carbon atoms.
•This process is called fractional distillation
Problems with
burning
hydrocarbons
Burning fuels Acid rain
• Sulphur dioxide and oxides of nitrogen
cause acid rain
Burning fuels Global warming
Carbon dioxide
causes global
warming
Burning fuels Global dimming
• Solid particulates cause global dimming
Burning fuels Removing sulphur
• Sulphur can be removed from fuels before they are
burned, for example in vehicles.
• Sulphur dioxide can be removed from waste gases
after combustion for example in power stations
Cracking
Cracking
• The vapours are either passed over a hot
catalyst or mixed with steam and heated to a
very high temperature so that thermal
decomposition reactions then occur
Alkenes
• Alkenes are unsaturated hydrocarbon molecules: contain at
least one C=C double bond
• Alkenes have the general formula CnH2n
Testing for
double bonds
Testing for alkenes
• Alkenes react with bromine water,
turning it from orange to colourless
Polymers
Polymerisation
• Alkenes can be used to make polymers such as
poly(ethene) and poly(propene).
• In these reactions many small molecules (monomers) join
together to form very large molecules (polymers)
Polymers- plastic bags
Advantages of plastic bags
Disadvantges of using plastic bags
Reuse & recycle- saves raw materials Non biodegradable
/ crude oil
Fills up land fills and land fills are an
Reuse & recycle- saves energy
eyesore
Reuse & recycle- cuts down on CO2
emissions
Reuse & recyle- Less global warming
Burning- can use them to make
energy
Burning can increase CO2
Burning can increase global warming
Producing ethanol - steam
• Ethanol can be produced by hydration of
ethene with steam in the presence of a
catalyst
Vegetable oils
Plant oils
• The plant material is crushed and the oil removed
by pressing or in some cases by distillation.
• Water and other impurities are removed
Plant
material
Crushed
Pressed
or distilled
Water & impurities
removed
What are the differences between fats?
Saturated fats contain no carbonto-carbon double bonds. The
straight fatty acids chains pack
closely together.
Unsaturated fats contain at least one
carbon-to-carbon double bond. This
bends the fatty acid chains and they
cannot pack closely together.
Saturated fats are less healthy than unsaturated fats
because the dense packing makes them harder for the
body to digest.
Making margarine
• Hydrogen adds to the carbon=carbon double bonds.
• The hydrogenated oils have higher melting points so they
are solids at room temperature, making them useful as
spreads and in cakes and pastries
Oil and water
• Oils do not dissolve in water
• They can be used to produce emulsions
Emulsifier molecule - Higher tier
• Emulsifiers have hydrophilic and hydrophobic
properties
Earth’s
structure
The Earth’s structure
The Earth’s movement
• The Earth’s crust and the upper part of the mantle are
cracked into a number of large pieces (tectonic plates)
Evidence for Wegener’s theory...
• Continents fit together like a jigsaw puzzle
• Similar fossils and rocks found on coastlines of
continents
How do tectonic plates move?
• Radioactive processes in
earth’s core release heat...
• ...Heat creates a convection
current in mantle...
• ...which moves the plates
Why can scientists not accurately predict
when earthquakes will occur?
• Earthquakes involve sudden movements
between plate boundaries so...
• ...so don’t know where or when the
force/ pressure is building up – and
reaches its limit
The Earth’s atmosphere today
How was our atmosphere formed?
•
•
•
•
First billion years - there was intense volcanic activity.
This activity released the gases that formed the early atmosphere and water vapour
that condensed to form the oceans.
There may also have been water vapour and small proportions of methane and ammonia.
Plants produced the oxygen that is now in the atmosphere
Tips for the
exam
Long exam questions – 6 marks
For 6 marks:
3 advantages/ disadvantages
Use of key scientific words
Excellent spelling
Excellent grammar and punctutation
No bullet points!
Some extra stuff...
Reliable
Repeating tests, checking results, having a
bigger sample
Valid
Keep everything the same except the
independent & dependent variables
Precision
Smaller scale division on equipment
Claims
You decide if it is true or false by looking at
evidence , independent organisations avoid bias
Ethical issues
Religious reasons, suffering, human rights
Environmental issues How does it affect the atmosphere / global
warming, habitat destruction
Key words
• Range = from smallest to biggest values
• Interval = what the values go up by
Eg: 2, 4, 6, 8, 10: Interval = 2
Don’t forget...
Describe a graph
Refer to the pattern e.g.
as……...increases………increases etc
Explain
Describe & give a reason “because…….”
Evaluate
For & against
Compare
What is the same & what is different
Calculate
Show calculations & give units
Suggest a reason
This should be scientific
Some final tips...
• Read the whole Q – 33% of the Qs can be
answered from information given to you in
text, diagrams, graphs & tables
• Follow instructions – “tick one box” “tick two
boxes” “use info from the table”
• Don’t write “it” – “the concentration
increases” NOT “it increases”
• What is the Q asking you to do?
Remember...
• 1 mark per minute – you have 45
minutes to answer 45 marks
• Use bullet points – 3 marks should
mean 3 bullet points
Good luck!
