Revision Notes C1 C1.1 Fundamental ideas - PowerPoint Presentation

Slide1

Revision Notes C1Slide2

C1.1 Fundamental ideas

Atomic Number

=

The number of protons in each atom of an element e.g. oxygen = 8.Mass Number = The number of protons AND neutrons in each atom of an element e.g. oxygen = 16. Mass Number will always be the bigger number.In an atom the number of protons = number of electrons. (This is why atoms are always neutral…no overall charge)Number of neutrons = Mass number - Atomic numberSlide3

C1.2 Limestone and it uses

Limestone is a rock made of calcium carbonate (CaCO

3

). Metal carbonates undergo thermal decomposition (they break down when heated) producing carbon dioxide:

CaCO

3

→

CaO

+ CO

2

A rotary kiln does this on a huge scale to make calcium oxide from limestone.

Metal carbonates also react with acid to make a salt, water and carbon dioxideCaCO3 + 2HCl → CaCl2 + H2O + CO2We test for carbon dioxide gas by bubbling it through limewater and seeing if it goes cloudy. Limewater is calcium hydroxide and reacts with CO2 to make calcium carbonate which is insoluble.Ca(OH)2 + CO2 → CaCO3 + H2O.Calcium hydroxide is made by adding water to calcium oxideCaO + H2O → Ca(OH)2These reactions represent the limestone cycle opposite (except the one with acid)

The limestone cycle:

Cement is a mixture of clay and calcium oxide. When mixed with sand and water it makes mortar. If we add small stones as well it becomes concrete. Concrete hardens over time as it reacts with CO

2 to become CaCO3 again. Concrete can be made even stronger by reinforcing it with steel rods. Limestone is quarried in areas of countryside. This can be a nuisance as it scars the landscape and creates a lot of noise and dust but creates lots of jobs bringing money to an area.Slide4

C1.3 Metals and their uses

Three ways of extracting metals from their ores.

Reduction with carbon

Electrolysis

Displacement

An ore is a rock that contains enough of the metal to make it worth extracting

1. Any metals lower than carbon in the reactivity series can be obtained by reduction with carbon. The metal oxide is reduced (loses oxygen) to give the metal and CO

2

.

Iron Oxide + Carbon → Iron + Carbon Dioxide

Zinc Oxide + Carbon

→

Zinc

+ Carbon

Dioxide

Iron is obtained from iron oxide by heating with carbon in a blast furnace. Steel is an

alloy of iron as the metal contains more than one element (iron + carbon). Alloys are much stronger than the pure metal. Stainless steel is very useful as it

does not corrode

.

Aluminium is a very light metal. It is extracted by electrolysis of aluminium oxide. This is very expensive as it needs a lot of electricity. Aluminium is unreactive as the metal forms a protective coating of aluminium oxide. Recycling aluminium

is

very important

as it saves energy/fuel, conserves ores and does not waste

space in landfill.

Titanium is

much stronger

than aluminium but even more expensive to make as it is

extracted

by

displacement with Mg.

Copper is extracted by smelting:

Copper

S

ulfide

+ Oxygen → Copper +

Sulfur

Dioxide

The copper is then purified by electrolysis to make very pure copper for electrical wiring.

Low-grade ores contain small amounts of copper. We extract the copper from these by using bacteria (bioleaching) or plants to absorb the copper into their roots (phytomining). We harvest and burn the plants to get the copper. Both of these green methods take a long time.

We can make an alloy of any metal to

change it’s properties (eg strength)Slide5

Alkanes

are hydrocarbons – they contain

carbon

and hydrogen only. Monkeys Methane CH4 Eat Ethane C2H6 Peanut Propane C3H

8

Butter

Butane C

4

H

10Alkanes have the formula CnH

(2n+2)

C1.4 Fuels from Crude OilBurning hydrocarbons in oxygen produces carbon dioxide and water.ALKANE + OXYGEN CARBON DIOXIDE + WATERWe can use this show this with this equipment:The carbon dioxide will turn the limewater cloudy

The water will condense in the U-tube and cause any indicator to change colour.

Fractional distillation separates crude oil into fractions containing similar sized hydrocarbon molecules. The crude oil is vaporised at high temperature and passed into a fractionating

column. The column is hot at the bottom and cool at the top. As the vapour rises up the column, different fractions condense at their boiling point and are collected. Big hydrocarbons

have high boiling points and are collected at the bottom of the column. Small hydrocarbons have low boiling

points and are collected at the top

of the column. Slide6

C1.4

Green Chemistry

Burning hydrocarbons in oxygen produces carbon dioxide and water.

ALKANE + OXYGEN CARBON DIOXIDE + WATERWe can show this with the set-up below:The carbon dioxide will turn the limewater cloudy

The water will condense in the U-tube and cause any indicator to change colour.

Burning fossil fuels releases carbon dioxide, CO

2

. Carbon dioxide is a greenhouse gas. It traps heat in the earth’s atmosphere and causes global warming.

Burning diesel also produces particulates (soot) – these small carbon particles. Slide7

Cracking

= Big alkane Small alk

ane

+ Small Alkene Octane Hexane +

Eth

ene

How?

Heat and catalyst

Why? Turn useless

big alkanes into small

alkanes (fuel) and alkenes (to make polymers and ethanol)

Polymerisation: Many small molecules (monomers) joined togetherto make very large molecules (polymer)C1.5 Products from Oilmonomer polymer ethene poly(ethene

) n is a very large number

Unsaturated – alkene - C=C double bondsBromine water tests for these. This is orange but goes colourless if C=C present

.If bromine water stays orange its alkane – saturated – C-C bonds only

Smart polymers have properties which change depending on their surroundings e.g. shrink as they warm up

Plastic waste is a big problem. We can:Burn it to provide energy (but that’s dirty)Recycle and make into other products

Dump as landfill (not very green)

Plastics from crude oil do not break down. We can make biodegradable plastics from plants (PLA -

cornstarch

) which do break down. These are also renewable (unlike plastics from crude oil) but people may starve as less land used to grow food.

Ethanol

: From plants or oil?

Hydration

(from oil):

Ethene

+ Steam Ethanol

Fermentation

(from plants):

Glucose Ethanol + Carbon dioxideSlide8

2 methods of extracting plant oils

Pressing

Steam Distillation

Unsaturated

means

C=C

double bonds

Bromine water

tests for these. This is orange but goes

colourless if C=C present

.

Cooking with oils (frying):Good: Nice taste and texture Energy rich Nutrients eg Vitamin E Quick (higher temperature)Bad: Make you fat if eat too muchHardening: Turn oils to solid fat (margarine)Why? Make spreadableHow? Hydrogen / 60

oC / Nickel catalyst

Emulsions

: Mixture of two

immiscible

liquids (oil and water).

Examples: Mayonnaise, Milk, Paint

Why? Nicer,

thick

er

texture

.

Good coating ability

(dipping chips in sauce)

How? Add

emulsifier

– chemical that forces oil and water to mix…

C1.6 Plant Oils

Hydrophilic head

a

ttracted to

water

Unsaturated Saturated

C=C C-C

Emulsifier Emulsion

Unsaturated fats (C=C)

good for you

Saturated fats (C-C only)

bad for you

Monounsaturates

have one C=C

Polyunsaturates

have more than one C=C

E numbers are food additives…chemicals added as emulsifiers, preservatives or for colour

Hardening oils

increases melting point

so solid at room temperature

Hydrophobic tail

a

ttracted to oilSlide9

Radioactive decay

in the

core

releases

heat

which causes

convection currents

in the

mantle

.

Tectonic plates

can move on these currents.Wegener believed South America and Africa were joined together a long time ago. He believed this because:Coastlines fit together like a jigsawSimilar layers of rock on both coastlines.Similar fossils on both coastlines.

The edges of tectonic plates are called plate boundaries. We can get

earthquakes or volcanic eruptions at these but it is difficult to predict them as we cannot see under the earth’s surface.Volcanoes formed our early atmosphere which was mainly water vapour and carbon dioxide. The water vapour condensed and formed the

oceans. The carbon dioxide has been ‘locked up’ in carbon sinks (sedimentary rock, fossil fuels, oceans). Plants also changed carbon dioxide into oxygen during photosynthesis.In the Miller-Urey experiment they showed it was possible to make

organic compounds from simple molecules in the early atmosphere (hydrogen, ammonia, water and methane) but they cannot make living things. Other possibilities are meteors or developed in volcanic vents under the sea.

Fractional distillation is used to separate the gases in air. They are cooled to make liquid air (the solid carbon dioxide and water are removed) and then warmed up slowly so they boil one at a time.

C1.7 Our changing planet

The

carbon cycle

balances the amount of carbon dioxide in the atmosphere. Burning fossil fuels is upsetting the carbon cycle causing

global warming

and making

the sea more

acidic

.

p

rimordial

soup