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Core Chemistry
73 cards·by olimyers1919
What is the general formula of an alkane?
CnH2n+2
Name the alternative word for 'burning in air'
combustion
Are alkanes saturated or unsaturated?
saturated
At room temperature, what state is a small hydrocarbon?
gas
At room temperature, what state is a large hydrocarbon?
solid
What is distillation used for?
separating a pure liquid from a mixture of liquids
What is the sequence of events in distillation?
heating-evaporation-cooling-condensation
What are the products of complete combustion?
water + carbon dioxide
What are the products of incomplete combustion?
water + carbon monoxide + carbon
How can sulfur dioxide be removed from waste gases after the combustion of fuel?
treated with powdered limestone to form calcium sulfate
What is the role of carbon dioxide in the greenhouse effect?
it absorbs heat energy and prevents it from escaping from the Earth's surface into space
What will happen as a result of melting polar ice caps?
increased coastal erosion and flooding of low-lying land
What is the cause of global dimming?
tiny particles that are released during combustion
What is the effect of global dimming?
less sunlight reaching the Earth's surface
What are the products of the thermal decomposition of calcium carbonate?
calcium oxide + carbon dioxide
How can we test for carbon dioxide after the thermal decomposition of a metal carbonate?
using limestone - it turns cloudy white when carbon dioxide is bubbled through it
How is quicklime produced from limestone?
thermal decomposition
How is slaked lime made from limestone?
thermal decomposition + water
Why is limestone used in the manufacture of glass?
to stop the glass dissolving in water
Why is sodium carbonate used in the manufacture of glass?
to reduce the melting temperature, making it cheaper
Wht are two advantages of the limestone industry?
useful for making things such as glass and concrete, provides employment opportunities
What are two disadvantages of the limestone industry?
may permanently disfigure the local environment, creates noise and heavy traffic
What is the disadvantage of limestone as a building material?
reacts with carbon dioxide in rainwater and slowly wears away
What is the disadvantage of concrete as a building material?
concrete structures are commonly viewed as unattractive
What is an advantage of concrete as a building material?
it is easily formed into different shapes before it sets hard
What is an advantage of glass as a building material?
lets lots of light in
What is a disadvantage of glass as a building material?
buildings with lots of glass can be too hot in the summer
What is an ore?
rocks that contain metal or metal compounds in sufficient amounts to make it economically
worthwile extracting them
How are the most reactive metals extracted from their ores?
electrolysis
How are the reasonably reactive metals extracted from their ores?
reaction with carbon or carbon monoxide
What compound do iron ores (e.g. haematite) contain?
iron oxide
What is the name for reactions in which oxygen is removed?
reduction
What is the function of coke in the blast furnace?
burns in air to produce heat, and reacts to form carbon monoxide - needed to reduce the iron
oxide
What is the function of limestone in the blast furnace?
helps to remove acidic impurities from the iron by reacting with them to form molten slag
What is the function of air in the blast furnace?
allows coke to burn
How is carbon removed from pure iron?
by blowing oxygen into the molten metal, forming carbon monoxide and carbon dioxide
What is a property of stainless steel?
resistant to corrosion
What is the name for a mixture of two or more elements, where at least one element is a metal?
alloy
What are smart alloys?
alloys which return to their original shape after being bent
What are some properties of transition metals?
good conductors/easily bent/high densities/high melting points
Why is copper useful for plumbing?
it does not react with water
What is meant by
ores which contain little of the desired metal element and a lot of waste rock
Why are aluminium and titanium resistant to corrosion?
they have a thin layer of their oxides on their surface, which stops water and air getting to the
metal
How is titanium used in medicine?
for artificial hip joints
Why is aluminium extraction expensive?
requires a lot of energy
Why is titanium extraction expensive?
the process involves several stages
Why is aluminium extensively recycled?
less energy is needed to produce recycled aluminium than to extract aluminium from its ore
What is continental drift?
the movement of tectonic plates that allow continents to shift apart
What causes tectonic plates to move?
convection currents in the mantle - caused by heat produced by the decay of radioactive
elements
Why did it take more than 50 years for Wegener's theory to be accepted?
it was difficult to work out what the mechanism was that could make the plates move
What is the main piece of evidence for Wegener's theory?
similar fossils on both sides of the Atlantic
What is the main gas in the Earth's atmosphere, and what percentage?
nitrogen - 78%
What percentage of the Earth's atmosphere is oxygen?
21%
What is the main property of noble gases?
they are chemically unreactive
What is argon used for?
light bulbs
What is krypton used for?
laser eye surgery
How was the Earth's early atmosphere formed?
from the gases given out by volcanoes
Why did the carbon dioxide levels in the Earth's atmosphere fall?
photosynthesis, locked up in rocks, dissolved in oceans
How is oil obtained from plant material?
the plant material is squeezed and crushed
What do molecules of vegetable oils contain?
fatty acids and glycerol
How can carbon-carbon double bonds be tested for in unsaturated oils?
using bromine or iodine
What happens when bromine water is shaken with an alkene?
it becomes colourless
What can be used to speed up hydrogenation?
a nickel catalyst
What is meant by the term 'carbon neutral'?
as much carbon dioxide is released as produced
Why do people say it is unethical to use biodiesel?
food crops should be used only to feed hungry people
Why are partially hydrogenated vegetable oils unhealthy?
they contain trans fats
What does an E number indicate?
the substance is licensed by the EU
What is cracking?
when large hydrocarbon molecules are broken down into smaller hydrocarbon molecules, by
being passed over a hot catalyst
Are alkenes saturated or unsaturated hydrocarbons?
unsaturated
Why can alkenes be used as fuels?
their double bonds allow them to react with oxygen
How is sugar from plant material converted into ethanol and carbon dioxide?
fermentation
Why can alkenes act as monomers?
they have a double bond
What are plasticisers?
substances that let polymer molecules slide over each other more easily