Chemistry Flashcards
How was the Earth’s early atmosphere formed?
By volcanic activity
What did the Earth’s early atmosphere consisit of?
It probably mainly consisited of carbon dioxide, probably with nitrogen and water vapour. There may have been traces of methane and ammonia.
What effect did plants spreading and developing have on the atmosphere?
They started to photosynthesis so the levels of oxygen in the atmosphere increased and the levels of carbon dioxide decreased.
How did the amount of carbon dioxide decrease?
- by algae and plants photosynthesisimg.
- by the formation of sedimentary rocks and fossil fuels that contain carbon.
- by being dissolved into the sea and then falling into the sea beds forming carbonate rocks.
How was the ammonia and methane in the early atmosphere removed?
Any ammonia and methane in the early atmosphere was removed by reactions with oxygen produced from photosynthesis.
Roughly, what is in the atmosphere today?
In today’s atmosphere, it’s about 80% nitrogen and 20% oxygen with small traces of other gases
What is one of the main reasons for the amount of carbon dioxide increasing in the recent past?
It is largely due to fossil fuels being burnt.
It’s hard to predict the effects on climate change of the rising levels of greenhouse gases on a global scale, however…
… most evidence suggests that the greenhouse gases from human activities will increase global temperatures.
How can the use of fossil fuels be reduced?
By using alternative sources of energy. However the change will cost money.
What risks are rising due to global climate changes?
- rising sea levels
- threats to ecosystems
- different patterns of food production
What can be caused by burning fuels?
Sulphur impurities in fuels burn to make sulphur dioxide which can cause acid rain.
When hydrocarbon fuels are burnt in plenty of air carbon dioxide and water are produced.
In insufficient oxygen, poisonous carbon monoxide gas can be produced. Particles of soot and unburnt hydrocarbons can be produced, causing global dimming.
Describe the differences between pure and impure substances.
Pure substances only contain one substance (can be elements or compounds) but impure substances are a mixture of two or more different elements or compounds.
Pure substances have specific melting and boiling points but impure substances melt/boil at a range of temperatures.
What are formulations?
useful mixtures made up in definite proportions, designed to give a product the best properties possible to carry out its function.
Rf =
distance moved by substance
________________________
distance moved by solvent
How do you test for hydrogen?
Place a lit splint in a test tube of hydrogen, if hydrogen is present there will be a “squeaky pop”
