Chemistry 1 - Core Flashcards
What is the Earth surrounded by a thin layer of?
Atmosphere
What does the atmosphere contain?
78% nitrogen 21% oxygen 1% argon (other noble gasses) Small amounts - water vapour, carbon dioxide and particulates) CO2 - 0.035%
When was the Earth formed?
4.6 billion years ago
What did the earliest atmosphere contain?
Ammonia, water vapour, carbon dioxide
How did the seas form?
From water vapour in the atmosphere
What lead to the decrease in atmospheric carbon dioxide, and increase in oxygen?
The evolution of photosynthesising organisms
What happened to carbon dioxide after it dissolved in the oceans?
Carbon became locked up in sedimentary rocks as carbonates and fossil fuels
What are pollutants?
Chemicals that harm the environment and our health
What can pollutants affect directly?
Food chains, health etc
How can pollutants have an indirect effect?
Through acid rain etc - it causes things which in turn have an effect
What is carbon dioxide harmful to and how?
The environment - traps heat in the earths atmosphere - leading to global warming
What is nitrogen oxide harmful to and how?
The environment and humans - can cause acid rain and breathing problems and make asthma worse
What is sulfur dioxide harmful to and how?
The environment and causes acid rain
What is carbon monoxide harmful to and how?
Humans - displaces oxygen in blood - binds to oxygen cite on red blood cell permanently
What are particulates harmful to and how?
Environment, humans, make buildings dirty - make asthma and lung infections worse if inhaled
How is pollutant concentration measured?
In Parts Per Million (ppm) and Parts Per Billion (ppb)
What can affect the measuring of pollutants?
1- variables (volume of traffic and weather)
2- measuring equipments accuracy
3- use of skill (will effect the use of accuracy and precision)
What are outliers?
They do not follow the general pattern of data - normally indicate some form of error
Why is it important to repeat measurements?
A single set of data may not be reliable - you cannot tell
How can you overcome small variations and get an estimate of the true value?
By calculating the mean
Where do the carbon monoxide emissions come from?
Around half from road transport, the rest from homes and other idustries
What is the correlation between carbon monoxide in the city and in the country park?
The mean carbon monoxide in the city is significantly higher than the park, supporting the theory it is produced by humans
What are elements?
The building blocks for all materials
How many elements are there?
Over 100
What are elements made up of?
Very tiny particles called atoms
What is specific about the atoms in one element?
They are all the same, and are unique to that element
What happens when atoms join together?
They form bigger building blocks called molecules
How are compounds formed?
When the atoms of two or more elements join chemically
What are chemical symbols and numbers used for?
To write formulae
What do formulae show?
The different elements that make up compound
The number of atoms of each different element in each molecule
What happens during a chemical reaction?
New substances are formed from old ones
Why are new substances formed during a chemical reaction?
The atoms in the reactants (starting substances) are rearranged in some wau
Can chemical changes be reversed?
Not easily
What is oxidation?
A chemical reaction that occurs when oxygen joins with an element or compound
What is reduction?
When oxygen is lost from a substance
What is combustion?
A chemical reaction that occurs when fuels burn, releasing energy as heat
What must be present for combustion to take place?
Oxygen
What is combustion an example of?
Oxidation
What is coal?
A fossil fuel containing mostly carbon
What is not produced during a chemical reaction?
Atoms
What happens to the number of atoms during a reaction?
It remains the same on either side of the equation - maintain mass
What is one result of the conservation of atoms during a reaction?
The production of some pollutants
Fossil fuels consist mainly of what compounds?
Hydrocarbons
What causes a burning reaction to be more rapid?
When fuel burns in pure oxygen rather than air
What is causes when a fuel is burned without the presence of enough oxygen?
Incomplete combustion
What does incomplete combustion lead to?
The production of carbon particulates or carbon monoxide
What can high temperatures during fuel combustion lead to?
Nitrogen in the atmosphere reacting with oxygen to form nitrogen oxides
What are the stages of nitrogen oxides production?
nitrogen reacting with oxygen - produce nitrogen monoxide
nitrogen monoxide is then oxidised - produce nitrogen dioxide
What are NO and NO2 called when together?
oxides of nitrogen (written as NOx)
What happens to carbon particulates once in the atmosphere?
They are deposited on surfaces (buildings etc) making them dirty
What happens to carbon dioxide when in the atmosphere?
Some is removed by plants during photosynthesis, some dissolves in rain and sea water where it reacts with other chemicals in the water
Each year what happens to the amount of atmospheric carbon dioxide?
It rises as we are producing too much to use up naturally
What produces acid rain?
Sulfur dioxide and nitrogen dioxide dissolved in water
What can acid rain do?
Cause damage to trees, erode stonework, corrode metal, upset pH balance of rivers and lakes - if water is too acidic, plants and animals will die - effecting entire food chain
How do scientists find out exactly how air quality affects up?
By looking for correlations that might link a factor to an outcome
How do scientists specify the outcomes to individual factors?
By carrying out secondary tests, eliminating all other variables
How do you know if results are reliable?
When the test can be repeated multiple times and receive the same outcome
Emissions from power stations can be removed by?
1- using less electricity so fewer fossil fuels need to be burned
2- removing toxic chemicals before they are burned
3- using alternative, renewable sources of energy
4- using a filter system to remove sulfur dioxide and particulates from flue gasses before they leave a coal burning power stations chimney
How is sulfur dioxide removed from flue gases?
By wet scrubbing using an alkaline slurry or seawater
What happens during wet scrubbing?
The sulfur dioxide in the flue gas is dissolved when contacted by a slurry of either lime stone (calcium carbonate) or lime (calcium oxide) and water. The absorbed sulfur dioxide is converted into calcium sulfate.
What happens during sea water scrubbing?
Sulfate salts are produced when the acidic dissolved sulfur oxides, produced when the sulfur oxides react with sea water, react with alkalis.
Emissions from motor vehicles can be reduced by?
1- buying a car with a more modern engine which is more efficient and burns less fuel
2- buying a hybrid car - uses electric power in the cities/ fuel for longer journeys
3- using a low sulfur fuel
4- converting the engine to run on biodiesel, a renewable fuel
5- using public transport to reduce the vehicles
6- ensuring cars are fitted with catalytic converters
What is a catalytic converter?
It reduces the amount of CO2 and nitrogen monoxide emitted - contains a catalyst in the exhaust of a vehicle which converts pollutant gases into less harmful ones
What are the benefits of recycling?
Helps to conserve natural resources
Saves energy - takes around 95% less energy to recycle and aluminium can than to make a new one
What has to happen when making national choices?
The benefits and needs must be weighed up against the problems
