Yr 9 Second Assessment Flashcards
Stages of the Earth’s evolution
Stage 1: -Earth cools to form a crust > volcanoes produce molten lava, carbon dioxide, methane, water vapour and ammonia gases
Stage 2: -Earth cools below 100°C > water vapour begins to condense, falls as rain
- rains for a long, long time till oceans form
- most of carbon dioxide and ammonia gets dissolved in the oceans
Stage 3: -3 billion years ago, marine organisms (e.g. algae) form and their photosynthesis absorbs most of CO2
-reduces greenhouse effect > temperature decrease
-photosynthesis makes more oxygen
> but oxygen doesn’t build up immediately, reacts with metals/elements to make oxides
>some reacts to make ozone layers
-levels of nitrogen and water increased because they oxygen reacted with methane and ammonia to form carbon dioxide+ water and nitrogen + water
Photosynthesis equation
carbon dioxide + water = glucose + oxygen
Ammonia + oxygen
= nitrogen + water
Methane + oxygen
= carbon dioxide and water
Respiration equation (reverse photosynthesis)
glucose + oxygen = carbon dioxide + water
Why is it helpful that photosynthesis is just reverse respiration?
-it balances out the carbon dioxide in the atmosphere
Nitrogen
-2 nitrogen atoms (N2)
-78%
-there is more of this substance than there is any other, it is quite unreactive
Oxygen
-2 oxygen atoms (O2)
-21%
-this is a vital element needed by living creatures for respiration
Carbon Dioxide
-1 carbon atom, 2 oxygen atoms (CO2)
-0.04%
-this substance is used by plants in photosynthesis
Hydrogen
-2 hydrogen atoms (H2)
-0.00005%
-this substance reacts with other substances when they burn
Argon
-1 argon atom (Ar)
-0.9%
-this element is made of atoms and doesn’t react with anything at all
Test for chlorine (Litmus paper)
- Take a test tube with your sample gas
- Dampen a piece of blue litmus paper
- Put it into the test tube
- If chlorine is present, the paper will turn from blue > white*
*the paper may briefly turn red before white, because the chlorine briefly dissolves in the water on the paper, which makes the paper red because its acidic
WEAR A MASK: CHLORINE IS POISONOUS
Test for oxygen (Glowing splint)
- Take a test tube with your sample gas
- Take a glowing splint (no flame, but still glowing red at end)
- Place splint into tube
- If oxygen is present, the splint will relight
*this is because burning requires oxygen
Test for Hydrogen (“Squeaky Pop Test”)
- Take a test tube with your sample gas
- Take a burning splint
- Place splint into tube
- When moved close enough together, a squeaky pop will be heard, if hydrogen is present
*this is because the heat energy (from the flame) causes the hydrogen to react rapidly with oxygen, and burn quickly.
>rapid release of energy in the form of a pop
Test for Carbon Dioxide (Limewater)
- Take a test tube with sample gas
- Connect it to a test tube with lime water Ca(OH)2 using a delivery tube with the bung
- Bubble gas sample through limewater
* if the gas is carbon dioxide, it will go cloudy because the carbon dioxide and limewater form calcium carbonate + water, and calcium carbonate is a solid so its particles make it APPEAR cloudy
Plants carry out ____________________. This is a process where the plant takes in __________ _____________ gas and water. The carbon dioxide is then locked up into ____________. This process also gives out ____________ gas. Animals carry out the process called _________________. In this process sugars react with oxygen to give __________ _____________ gas and ___________. Therefore photosynthesis and _______________ keep a balance of carbon ______________ and oxygen in the atmosphere.
Plants carry out photosynthesis. This is a process where the plant takes in carbon dioxide gas and water. The carbon dioxide is then locked up into sugars. This process also gives out oxygen gas. Animals carry out the process called respiration. In this process sugars react with oxygen to give carbon dioxide gas and water. Therefore, photosynthesis and respiration keep a balance of carbon dioxide and oxygen in the atmosphere.
Four gases present in the early atmosphere of the earth
-carbon dioxide
-water vapour
-methane
-ammonia
Where do scientists think that life first evolved?
-near underwater volcanoes, where there were loads of nutrients and raw materials
How did oxygen appear in the Earth’s atmosphere?
- from photosynthesis, when organisms started to evolve (e.g. blue algae)
When oxygen first arrived in the Earth’s atmosphere, it reacted with metals, like iron. Give the word equation for the reaction.
iron + oxygen -> iron oxide
What layer did oxygen form in the upper atmosphere?
-ozone layer
Why was the ozone layer important for life on land?
-shielded the Earth from harmful UV light from the sun, so the organisms could live on land
Natural processes which remove carbon dioxide from the atmosphere.
-photosynthesis
-reacts with the water in lakes +oceans , because it is partly soluble in water
-taken up by marine organisms, such as crustaceans, for their shells
-dead organisms fell to the seabed, got buried in layers of sediment, and over mills of years,
sediment compressed to sedimentary rock, oil +gas, trapping carbon,
Why has carbon dioxide increased over the last 100 years?
- burning of fossil fuels from cars/factories/air travel/power stations
- deforestation (less photosynthesis to absorb the carbon dioxide)
Atmosphere percentages
- Nitrogen (78%)
- Oxygen (21%)
- Argon (0.9%)
- Carbon dioxide (0.04%)
- Hydrogen (0.00005%)
What is the most common gas?
Nitrogen
How much of the Earth’s atmosphere is oxygen?
21%
Greenhouse gases
-greenhouse gases in the atmosphere maintain temperature on Earth high enough to support life
-they absorb UV and infra-red radiation from the Sun and emit them into the atmosphere
3 main greenhouse gases
-water vapour
-carbon dioxide
-methane
Greenhouse effect
- The Sun emits short-wavelength radiation, warming the Earth.
- The Earth loses heat through long-wavelength radiation (e.g. thermal infrared), with most escaping to space.
- Greenhouse gases absorb some long-wavelength radiation, stopping it from escaping.
- These gases re-radiate the thermal energy in all directions, including back to Earth.
Hydrocarbon
-organic chemical compounds made exclusively of hydrogen and carbon atoms
What happens when you burn fossil fuels? (e.g. coal, oil, gas)
-produces carbon dioxide + water
-releases lots of energy
Complete combustion
-when a hydrocarbon burns in plenty of oxygen:
hydrocarbon + plenty of oxygen -> water + carbon dioxide
Incomplete combustion
-when a hydrocarbon burns but there’s not enough oxygen available:
hydrocarbon + not enough oxygen -> particulates/carbon monoxide + water
Particulates
- solid particles of carbon
Problems of particulates/soot
- when inhaled, they get stuck in our lungs and damage them, leading to respiratory problems
- particulates also form dark clouds/smog, reflecting sunlight back into space, less light reaching the Earth (GLOBAL DIMMING)
What is global dimming?
- decline in the amount of sunlight reaching the Earth’s surface
Problems of carbon monoxide
-if breathed in from the air, it diffuses into our blood and binds to the haemoglobin
> so less oxygen gets transported round the body, potentially leading to fainting, coma or even death, as the brain is starved of oxygen
Why is carbon monoxide hard to detect?
- colourless and odourless
How is sulfur dioxide formed?
-sometimes the hydrocarbons can have impurities (e.g. sulfur atoms)
- so when they burn sulfur dioxide is produced
How are nitrogen oxides formed?
-when nitrogen + oxygen from the air react together
-rare as it requires super high temperatures
>temperatures are often reached inside internal combustion engines (e.g. cars)
Problems of sulfur dioxide and nitrogen oxides
- when breathed in, can damage lungs -> leading to respiratory problems
- when mixed with clouds, they dissolve to from dilute sulfuric acid or dilute nitric acid, falling as acid rain
ACID RAIN ⚠
-damages stonework (e.g. limestone)
-kills fish
-damages plants, either by landing directly on them or by making the soil more acidic
-corrodes metals
Flue gas desulphurisation
- remove sulfur dioxide by reacting it with calcium oxide or calcium carbonate ( CaO and CaCO3)
Catallytic converters
-catallytic converters in cars remove NO2 or NO3 (nitrogen oxides)
Equation for complete combustion
CH_4 + 2O_2 -> CO_2 + 2H_2_O
hydrocarbon + oxygen -> carbon dioxide + water
Equation for incomplete combustion
2CH_4 + 3O_2 -> 2CO + 4H_2_O
hydrocarbon + oxygen -> carbon monoxide + water
CH_4 + O_2 -> C + H_2_O
hydrocarbon + oxygen -> particulates + water
Fill in the blank: The primary function of a catalytic converter is to convert _____ and _____ into less harmful emissions.
carbon monoxide, nitrogen oxides
What is the purpose of flue gas desulphurisation?
To remove sulfur dioxide (SO2) from flue gases before they are released into the atmosphere.
Which of the following is a product of incomplete combustion? A) CO2 B) H2O C) CO D) O2
C) CO
How does methane increase?
-land fill sites
-farming
-growing rice
-natural gas and petroleum systems
Carbon footprints
-total emission of CO_2 and other greenhouse gases over the full-life cycle of a product
Life cycle assessment (LCA)
- technique used to assess the environmental impact associated with all the stages in the life cycle of a product, event, service
How to reduce a carbon footprint?
- walk instead of driving
- buy locally sourced food
- reforestation
- recycling
- use electric cars
How do big companies reduce their carbon footprint?
-carbon capture
> store it in the deep underground areas, in porous rocks, and years later, extract oil and gas
-renewable energy sources
Effects of climate change
-flooding
-extreme weather
-changes in rainfall
-extinction
Climate change
-long-term changes in global temperatures and other characteristics of the atmosphere
Peer- reviewing
- the evaluation of scientific work by other experts in the same field
Percentage change
(New- Old)/Old ×100
Photosynthesis symbol equation
6CO2 + 6H2O → C6H12O6 + 6O2
