Flashcards in Chemistry Deck (31)
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.
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"
How do you test for oxygen?
Put a glowing splint in oxygen and if oxygen is present it will relight the glowing splint.
How do you test for carbon dioxide?
Bubble carbon dioxide gas into a test tube of limewater and if it turns cloudy, then carbon dioxide is present.
How do you test for chlorine gas?
Damp, blue litmus paper turns white when chlorine gas is present.
Which scientists have helped to develop the model of the atom?
What can happen at high temperatures in engines?
At high temperatures in engines, nitrogen can react with oxygen in the air, forming oxides of nitrates. These can result in breathing problems and acid rain.
What are the three sub-atomic particles?
What are the three sub-atomic particles' relative charges and relative masses?
relative charge relative mass
neutrons 0 very small
protons +1 1
electrons -1 1
What is an atomic number?
Number of protons (=number of electrons too)
What is an atomic mass?
number of protons + number of neutrons
What do atoms that gain electrons form?
What do atoms that loose electrons form?
What are isotopes?
Atoms of the same element with different numbers of neutrons.
They have identical chemical properties, but their physical properties, such as density, can differ.
What did Dalton discover about the atom?
Discovered the atom
What did Thomson discover about the atom?
Discovered electron and made plum pudding model