The Earth s early atmosphere Mostly carbon dioxide with little or NO oxygen Early atmosphere formed by gases given out by volcanoes Smaller proportions of water vapour ammonia and methane Most of the water vapour condensed and formed oceans ID: 650366
Download Presentation The PPT/PDF document "Air Chapter 31 Page 186" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Air
Chapter 31 Page 186Slide2Slide3
The Earth
’
s early atmosphere
Mostly carbon dioxide with little or NO oxygen
Early atmosphere formed by gases given out by volcanoes
Smaller proportions of water vapour, ammonia and methane
Most of the water vapour condensed and formed oceans
Very similar to the atmospheres of Mars and VenusSlide4
Changes to the early atmosphereSlide5
What is air made of?
Air is a mixture of different gasses
Nitrogen N
2
Oxygen O
2Noble Gasses ArCarbon Dioxide CO2
Water Vapour H2OSlide6
Changes to today
’
s atmosphere
Where has this increase in carbon dioxide come from?
Burning fossil fuels!Slide7
How can we prove air is a mixture?
Its composition varies – in compounds the composition is constant
If air is cooled down to low temperatures the gasses all become liquids at different temperatures – in compounds gasses would change state at the same time
The components of air can be separated individuallySlide8
How can we prove air is a mixture?
When the gasses air mixed together in the right amounts they form air, no heat is given out or taken in so no new compound is madeSlide9
How can we show the amount of oxygen in air?
The candle uses up all of the oxygen in the air until it goes out. The level that the water rises could be used to calculate approx. that 21% of air is made up of oxygen.Slide10
How can we show that the air contains carbon dioxide?
Carbon Dioxide, turns lime water milky.Slide11
How can we show that the air contains water
vapour
?
Turns blue cobalt chloride paper pinkSlide12
Oxygen
Oxygen is prepared in the lab by looking at the breakdown of Hydrogen Peroxide
This is however a very slow reaction so we use a substance called a catalyst
A Catalyst is a substance that speeds up a chemical reaction without being used up in the reactionSlide13
Oxygen
Chemical equation:
2H
2
O2 2H2O + O2Hydrogen Peroxide Water + Oxygen
MnO2Manganese DioxideSlide14
Oxygen
Properties:
Oxygen is a
colourless
,
odourless, tasteless gasOxygen is slightly heavier than airOxygen is slightly soluble in waterOxygen is a neutral gas, it is not acidic or basic
5. Oxygen relights a glowing splint – this is the test for oxygen6. Oxygen is a very reactive element. It combines with other elements to form oxidesSlide15
Oxygen
Acidic – Carbon dioxide
C + O
2
CO2Basic – Magnesium Oxide2Mg + O2 2MgOSlide16
Oxygen
Uses:
Breathing – our cells need oxygen to release energy from our food
Welding – Cutting and welding requires a very hot flame, this is achieved when acetylene is mixed with oxygen
Burning – Oxygen is needed for the burning of fossil fuels Slide17
Preparing oxygen
We will look at this next weekSlide18
03/12/13Slide19
Preparing Oxygen
Today we will
Prepare oxygen using hydrogen peroxide and manganese dioxide
Conduct the tests for oxygenSlide20
Preperation of OxygenSlide21
Oxygen
Chemical equation:
2H
2
O2 2H2O + O2Word Equation :Hydrogen Peroxide Water + Oxygen
MnO2Manganese DioxideRemember:Reactants ProductsSlide22
Testing for Oxygen
Relight a glowing splint
Neutral – moist red and blue litmus stay red
and blueSlide23
10/12/13Slide24
Today we will…
Look at
the production of Carbon
dioxide
How it is produced
Its propertiesIts UsesWe will make some!Slide25
Carbon Dioxide
Carbon Dioxide can be prepared in the lab by reacting dilute, Hydrochloric acid and marble chips
Calcium
carbonate + Hydrochloric acid
Calcium Chloride + Water + Carbon Dioxide CaCO3
+ 2HCl CaCl2 + H2O + CO2Slide26
Properties of Carbon Dioxide
CO
2
is a
colourless, odourless, tasteless gasIt is an acidic gas – Turns blue litmus paper redDoes not support combustion (burning)It is denser than airSlide27
Properties of Carbon Dioxide
5. It
turns limewater milky – this is the test for carbon
dioxide
Ca
(OH)2 + CO2 CaCO3 + H2O
Limewater + Carbon dioxide Chalk + WaterSlide28
Properties of Carbon Dioxide
6. It dissolves in water to form an acidic solution that turns blue litmus paper red
CO
2
+ H
2O H2CO3Carbon dioxide + Water Carbonic AcidSlide29
Uses of Carbon Dioxide
Photosynthesis – green plants use it to make their food
Fire Extinguishers – puts out fires
Fizzy Drinks – It is dissolved under high pressure in fizzy drinksSlide30
The Production of CO
2
(
Pg
105)Slide31
Procedure
Set up as shown (calcium carbonate is the chemical name for marble chips)
.
Slowly release the hydrochloric acid into the flask underneath
.
Carbon dioxide is collected it the gas jarTest 1:Pour a small volume of limewater into the jar and shake – the limewater will turn milky showing that the gas is carbon dioxide.Test 2:Add water to a fresh jar of carbon dioxide and test with blue litmus paper: it turns red demonstrating that it is an acid.