Yr 9 Second Assessment Flashcards
(60 cards)
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)
