Chemistry Flashcards
What percentage is there of nitrogen in the air
78%
What percentage is there of argon in the air
0.9%
What percentage of co2 is there in the air
0.037%
What is wrong with the oxygen percentage test in which copper is heated up
There is air between the copper and the air in the gas syringe expands due to an next ease in temperature
How was the earths early atmosphere formed
Volcanic activity
What was the consistency of the earths early atmosphere
Mostly carbon dioxide
How many billion years was there intense volcanic activity to form the earths early atmosphere
1 billion
What gases other than co2 probably existed in the early atmosphere
Water vapour, ammonia, methane
How did the oceans get formed
The water vapour in the early atmosphere condensed because the earth cooled
Which to planets are believed to have early similar atmospheres compared to the early atmosphere of earth
Mars and Venus as their atmospheres consist mainly of carbon dioxide
Of they weren’t there how can scientists know the consistency o the early atmosphere
Scientists had to gain information from other sources for example:
Volcanoes on other planets release high quantities of carbon dioxide
Nitrogen and iron compounds present in very old rocks that could only have formed in an ocygen free environment
How did the proportions of oxygen in the early atmosphere go up and the proportion of carbon dioxide go down
The proportion of oxigen went up because of photosynthesis by plants
Carbon dioxide went down because:
It was locked up in sedimentary rocks like limestone, and in fossil fuels like oil
It was absorbed by plants for photosynthesis
It dissolved in oceans
How is the level of the current atmospheres co2 increasing
We are burning fossil fuels and adding co2 into the air faster than it can be removed
How is the level of carbon dioxide maintained
Photosynthesis
Green plants all remove co2 from the air through photosynthesis
Combustion
Releases co2 into the air
Respiration
Releases co2 into the air
Steps of the carbon cycle
Respiration and combustion out co2 into the air
Photosynthesis takes co2 out of the air
Animals eat plants and release co2 back into the air
Ways humans are increasing the atmospheres co2 content
With more people we burn more fossil fuels for energy
When land is cleared for timber and farms there are fewer trees to remove co2 this is extra bad when we clear trees for farmland by burning them
One does not always get the calculated amount of product from a reaction because;
Reversible reactions may not go to completion
Some products may be lost when it’s removed from the reaction mixture
Some of the reactants may react in an unexpected way
What is an example of conservation of mass
A precipitation reaction
Why is it easy to show conservation of mass in a precipitation reaction
All the reactants and products remain in the same sealed reaction container so it is easy to show the mass has not changed
What is copper sulphate
CuSO4
What is sodium hydroxide
NaOH
What colour precipitate does iron (II) produce
Green- turns brown when standing
What colour precipitate does iron (111)
Produce
Orangy brown
What colour precipitate does copper produce
Blue pale
What colour precipitate does zinc produce
White
4 features of acids
Have a low ph (1-6)
React with bases to form neutral compounds
Are corrosive when strong
Are irritant when weak
What is an indigestion remedy
An indigestion remedy contains a base like magnesium hydroxide which reacts to form a neutral compound and raises the oh of the stomach
What do you observe during a metal hydroxide and acid reaction
Temperature rise
The ph changes
What are the products in a metal hydroxide plus acid reaction
A salt and water
Are metal hydroxides soluble
Yes- they usually dissolve in water to form clear colour less solutions
Are metal oxides usually soluble
No but some of them such as sodium oxide can dissolve in water to form clear colourless solutions
What are the products of a metal oxide plus acid reaction
Salt and water
What can you observe during a metal oxide and acid reaction
Temperature rise and ph change
Are metal carbonates dissolve in water
No but sodium carbonate can (bicarbonate of soda) just remember that in both metal oxides and metal carbonates sodium is one of the only ones that dissolves
What are the products of a metal carbonate and acid reaction
A salt
Water
Carbon dioxide
What can you observe in an acid plus metal carbonate reaction
Bubbles being given off (co2)
A ph change
When hydrochloride acid reacts with a metal hydroxide carbonate etc is an ate or ide formed
It is always an Ide
When sulphuric acid reacts with an oxide hydroxide etcetera does it form an ate or an IDE
Always ate
What is electrolysis
Electrolysis is the process in which ionic substances are broken down into simpler substances using electricity. During electrolysis, metals and gases may form at the electrodes.
What is an ionic compound
The product of When a metal reacts with a non metal
What must the ions be to perform electrolysis
Free to move one does this by either dissolving the substance in water or melting it
How does electrolysis work
Positively charged ions move towards the negative electrode during electrolysis and receive electrons to turn them into their original form
Negatively charged ions move toward the positively charged electrode they lose electrons to form their original state and are oxidised
4 facts about the electrolysis of hydrochloric acid
Produces chlorine at the positive electrode
Produces hydrogen at the negative electrode
How to test for chlorine
Turns damp blue litmus paper red then white
The products of the electrolysis of water
Hydrogen at the negative electrode
Oxygen at the positive electrode
What percentage is the oxygen in the air
21%
What is reduction
The loss of oxygen from a substance many ores are oxides so one can extract metals through reduction
How do we extract very reactive metals compared to less reactive metals
The oxides of very reactive metals such as aluminium form stable oxides and other compounds
A lot of energy is needed to extract these this is often done through electrolysis
Less reactive materials such as iron can be split with their bonds fairly easily through reduction reactions using carbon
Unreactive metals like gold are extracted through various chemical reactions
What is rust a form of
Corrosion
What is rust
Hydrated iron (111) oxide
How to test that rust can not form with either water or air not present
For air but no water use calcium chloride so it reacts with any water in the test tube
For water but no air use boiled water with a layer of oil above it to stop air getting to it
What speeds up the formation of rust
Salt dissolved in water and acid
Why does aluminium not corrode
It is protected by a natural layer of aluminium oxide which stops the layer of pure aluminium coming into contact with air
Oxidisation on iron flakes off whereas oxidisation on aluminium does not
Use of metals: Aluminium Copper Gold Steal
Aluminium is low density and does not corrode so is suitable for bodies of planes
Copper is a good conducted of electricity and does not react with water so it is good for electrical wires and water pipes
Gold is a very good conducted and very unreactive so it is good for jewellery and electrical connections on circuit boards
Steel is cheap and strong so is suitable as a building material
How do alloys make a metal stronger
Alloys contain atoms of different sizes
Which distort the regular arrangement of atoms. This makes it harder for the layers to slide over each other so the metal is harder
What is brass and how is it used
It is an alloy of 70 percent copper and 30 percent zinc
What is 18 carat gold
75 percent gold and 25 percent copper
And other metals
What is duralumin
96 percent aluminium and 4 percent copper and other metals used in aircraft manufacture
Smart alloys
Smart alloys return to their original shape after being bent they are useful for spectacle frames and dental braces
What is an example of a smart alloy
Notinol returns to its original shape after being squealed by warming it
Notional tubes are used to open up arteries and as spectacle frames
What is nitinol made of
Nickel and titanium
What is an ore
A naturally occurring rock that contains metal or metal compounds at a sufficient amount to make it worthy to extract them
What is crude oil
A mixture of compounds called hydrocarbons
What is an alkane
A hydrocarbon with the formula
CnH2n plus 2
So an alkanes hydrogen is always double the amount of the carbon plus 2
What is meant by saturated hydrocarbon
The hydrogen is bonded to the carbon with double bonds making it relatively unreactive except for with oxigen
Alkanes are saturated
What are small hydrocarbons states
Gases
What are hydrocarbons with five to 12 carbons states
Liquids
Large hydrocarbons with many carbons are at which state
Solid
What is the sequence in events in distillation
Heating
Evaporating
Cooling
Condensing
What is complete combustion
The hydrogen in hydrocarbons oxidises to form water and the carbon oxidises to form carbon dioxide
Hydrocarbon+ oxygen=>water and carbon dioxide
What is incomplete combustion
Carbon monoxide produced, particles of carbon (seen as soot or smoke)
What happens to sulphur compounds in hydrocarbons when they are burnt
Soulful dioxide
What are the five gases that can be released into the air by the combustion of fuels
Water vapour Carbon dioxide Carbon monoxide Particles ( carbon) Sulphur dioxide
8 factors that have to be considered when deciding weather or not to use a fuel/ how to use a fuel
The energy value of the fuel in joules The availability of the fuel How the fuel can be stored The cost of the fuel The toxicity of the fuel Any pollution that the fuel may cause such as sulcus dioxide How easy it is to use the fuel
Positives of solid fuels (coal)
And negatives
Easier to store
Harder to light
Benefits of liquid and had fuels
Light easily
Flow through pipes
Problems with soulful dioxide
Causes acid rain when soulful dioxide dissolves in clouds
Effects of acid rain
Reacts with metals and rocks such as limestone buildings and statues are damaged as a result
Acid rain damages the waxy layer on leaves of trees and make it harder for plants to soak up the minerals they need for growth
Acid rain makes lakes and rivers too acidic for some aquatic life to survive
How is sulphur dioxide dealt with
It can be removed from waste gases after the combustion of the fuel by treating it with calcium carbonate to form calcium sulphate this can be used to make plaster board
What does a greenhouse gas do
Absorb thermal energy and prevent it from going back into space
The four steps of the greenhouse effect
The suns rays enter the earths atmosphere
Heat is reflected back off of the earths surface
Heat is absorbed by greenhouse gases such as co2 or methane
The earth gets hotter
Effect of global warming two things
Global weather patterns will change drought and flooding
Polar ice caps will melt raising sea levels increased coastal erosion and flooding of low lying land including land where major cities lay
How are scientists trying to control the amount of co2 in the atmosphere
Iron seeding of oceans
Converting carbon dioxide into hydrocarbons
Advantages of biofuels
Carbon neutral
Negatives about biofuels
Ethical issue that people think that it is bad to make fuel out of food crops
Problems with hydrogen fuel
Need electricity to produce which uses hydrocarbons to make
Not convenient, very flammable May explode must be compressed and chilled then stored in tough insulated tanks
What is the name for 1 2 3 and 4 carbons in a hydrocarbon
Meth
Eth
Prop
But
How is cracking done
Fractions containing large hydrocarbons are vaporised then passed over a hot catalyst to break them into smaller pieces
Why do we crack hydrocarbons
Large molecules aren’t efficient
They don’t flow easily
Crude oil often contains too many large hydrocarbons and too little small to meat demand
What is an Alkene
An unsaturated hydrocarbon this happens by the carbon atoms having double bonds
The formula for alkanes is to double the amount of carbons to get the hydrogens
Testing for alkenes
Bromine water is used
An Alkene will turn brown bromine water couler less as it reacts with the double bond
Use for alkenes
Polimers
What are Polimers
Very large molecules made when many smaller molecules join end to end the smaller molecules are called mine mets
Ethan can polomerise to form
Polyethene
Propane can polomerise to form
Poly proper
Use for poly ethane
Polypropene
Polychloerothene
Polyethene plastic bags and bottles
Polypropene crate and ropes
Polychlorothene water pipes and insulation
Uses of polymers
Ethane flexible cheap insulator plastic bags and bottles coating on wires
Proper flexible and strong buckets and crates
PVC tough cheap and long lasting window frames
Tetrafluoroethene tough and non stick
Coating on pans
Polymer problems
Are not biodegradable although chemicals can be added to make the degrade
When incinerated toxic gases are produced unless burning at very high temp
Problems with recycling
Difficult to seperate different plastics
