Name the fractions from fractional distillation of crude oil from the top to the bottom of the column
number of carbon and hydrogen atoms in the molecules, ease of ignition, viscosity, boiling points
How do hydrocarbons in different fractions differ from each other? (4 things)
Give an example of a homologous series
a series of compounds which: have the same general formula, differ by CH2 in molecular formulae from neighbouring compounds, show a gradual variation in physical properties, e.g. boiling points & have similar chemical properties
What is a homologous series?
What is the general formula of alkanes?
Name the alkane with the molecular formula CH4
What is the molecular formula of ethane?
Name this alkane
water and carbon dioxide are produced and energy is released
What happens during the combustion of hydrocarbon fuels?
carbon and carbon monoxide
What can be produced from the incomplete combustion of hydrocarbons?
there is not enough oxygen to fully oxidise all of the carbon atoms to produce carbon dioxide
Why can the incomplete combustion of hydrocarbons produce carbon and carbon monoxide?
It combines with haemoglobin in red blood cells which stops oxygen from being transported around the body
How does carbon monoxide behave as a toxic gas?
Soot can block pipes carrying waste gases away from an appliance, cause breathing problems if inhaled and blacken buildings
What problems can soot (unburnt carbon) cause?
sulfur impurities in the fuel combine with oxygen
Why is sulfur dioxide produced when hydrocarbons burn?
sulfur dioxide dissolving in rain water
What is the major cause of acid rain?
crops don't grow well, insects die, fish eggs don't hatch, buildings are weathered, metals corrode more quickly
What problems can acid rain cause? (5 things)
In the high temperatures inside the engine, nitrogen and oxygen react together.
How are oxides of nitrogen produced in cars?
The combustion of hydrogen doesn't produce carbon dioxide which is a greenhouse gas. Hydrogen can be produced relatively easily. Hydrogen is easy to ignite.
Give advantages of using hydrogen rather than petrol as a fuel in cars
Hydrogen is a gas at room temperature and so is difficult to store in large amounts unless it is compressed or cooled so that it becomes a liquid.
Give disadvantages of using hydrogen as a fuel in cars
the breaking down of longer chain hydrocarbons into smaller ones, some of which are unsaturated
What is cracking?
It produces more useful molecules
Why is cracking needed?
an unsaturated hydrocarbon
What is an alkene?
What is the general formula of alkenes?
What is the name of this molecule?
What is the molecular formula for propene?
Which hydrocarbon homologous series contains carbon-carbon double bonds?
by gases released from volcanic activity
How was the Earth's early atmosphere formed
little or no oxygen, a large amount of carbon dioxide, water vapour, small amounts of other gases
What did the Earth's early atmosphere contain?
condensation of water vapour
How were the oceans formed?
it dissolved as the oceans formed
How did the amount of carbon dioxide from the early atmosphere decrease?
by photosynthesis of primitive plants
How did the amount of oxygen in the atmosphere increase?
a glowing splint relights
What is the chemical test for oxygen?
gases in the atmosphere absorb heat radiated from the sun
What is the greenhouse effect?
carbon dioxide, methane and water vapour
Give examples of greenhouse gases
correlation between carbon dioxide emissions and temperature change
What evidence is there that human activity has caused climate change?
the location of measurements and the accuracy of historical data
What are the problems with data suggesting that human activity has caused climate change?
rising sea levels, extinction of species as their habitat changes, more extreme weather events, coral 'bleaching'
What are the possible effects of climate change?
Measuring the volume of gas produced or measuring the time taken for a colour change to happen
Give two ways of measuring the rate of reaction
Particles must collide with sufficient energy
What has to happen for a reaction to occur?
Increase the frequency and/or energy of collisions
How can the rate of a chemical reaction be increased in terms of collisions?
increase the temperature, increase the surface area, increase the concentration, increase the pressure
How can the rate of a chemical reaction be increased practically?
The rate of reaction is high
If a rate of reaction graph is steeper what does that mean?
The line levels off (is horizontal)
How can you tell from a rate of reaction graph that the reaction has stopped?
It reduced the activation energy so more collisions are successful
How does a catalyst increase the rate of a reaction?
a substance that speeds up the rate of a reaction without altering the products of the reaction, being itself unchanged chemically and in mass at the end of the reaction
What is a catalyst?
The minimum amount of energy that colliding particles need to have for a reaction to happen
What does the term activation energy mean?
a biological catalyst
What is an enzyme?
the production of alcoholic drinks
Give a use of enzymes
What word describes a chemical reaction where the surroundings get hotter?
a reaction where heat energy is given out
What is an exothermic reaction?
What word describes a chemical reaction where the surroundings get colder?
a reaction where heat energy is taken in
What is an endothermic reaction?
dissolving, precipitation, neutralisation and displacement
Give four examples of reactions that involve changes in heat energy
Is bond breaking exothermic or endothermic?
Is bond making exothermic or endothermic?
If more heat energy is released in forming bonds in the products than is required in breaking bonds in the reactants what sort of reaction is it?
If less heat energy is released in forming bonds in the products than is required in breaking bonds in the reactants what sort of reaction is it?
Is this an exothermic or endothermic reaction?
Draw the energy level diagram for an endothermic reaction
sub-atomic particles were discovered
Why did the Dalton model of the atom change over time?
protons and neutrons
Which sub-atomic particles are in the nucleus?
in shells around the nucleus
Where are electrons found?
What is the relative charge of a proton?
What is the relative charge of a neutron
What is the relative charge of an electron?
What is the relative mass of a proton?
What is the relative mass of a neutron?
What is the relative mass of an electron?
How big is the nucleus compared to the overall size of the atom?
concentrated in the nucleus
Where is most of the mass of an atom?
the number of protons + the number of neutrons
What is meant by the term 'mass number'?
they contain the same number of protons
What do atoms of an element have in common?
Atoms of an element with the same number of protons but a different number of neutrons
What is an isotope?
because of the existence of isotopes
Why are relative atomic masses of some elements not whole numbers?
properties of elements and their compounds
What did Mendeleev use to make his Periodic Table?
in terms of increasing atomic mass
How did Mendeleev think he had arranged the elements?
a row going across
What is a period on the Periodic Table?
a column going down
What is a group on the Periodic Table?
in order of increasing atomic number
How are elements arranged in the Periodic Table?
they have the same number of electrons in their outer shell and similar properties
What is true about elements in the same group in the Periodic Table?
If an element is in group 1, how many electrons are there in the outer shell?
If an element is in group 2, how many electrons are there in the outer shell?
If an element is in group 3, how many electrons are there in the outer shell?
If an element is in group 6, how many electrons are there in the outer shell?
If an element is in group 7, how many electrons are there in the outer shell?
by the transfer of electrons
How are ionic bonds formed?
an atom or groups of atoms with either a positive or negative charge
What is an ion?
If an element is in group 1, what will the charge on the ion be?
If an element is in group 2, what will the charge on the ion be?
If an element is in group 6, what will the charge on the ion be?
If an element is in group 7, what will the charge on the ion be?
If the name of a compound ends in -ate, which element must it contain?
What is the formula for a hydroxide ion?
a giant ionic lattice
What is the structure of an ionic compound?
strong electrostatic forces (ionic bonds)
What holds together an ionic compound?
a metal ion and a non-metal ion
What are ionic compounds made from?
a positive ion
What is a cation?
a negative ion
What is an anion?
positive ions (cations)
What sort of ions do metals form?
negative ions (anions)
What sort of ions do non-metals form?
a shared pair of electrons between atoms
What is a covalent bond?
What sort of bonding results in the formation of molecules?
100 pm (1 x 10^-10 m)
Approximately how big is an atom?
200 pm (2 x 10^-10 m)
Approximately how big is a molecule?
Draw a dot-cross diagram to show the bonding in hydrogen molecules.
Draw a dot-cross diagram to show the bonding in hydrogen chloride molecules.
Draw a dot-cross diagram to show the bonding in water molecules.
Draw a dot-cross diagram to show the bonding in methane molecules.
Draw a dot-cross diagram to show the bonding in oxygen molecules.
Draw a dot-cross diagram to show the bonding in carbon dioxide molecules.
high because of the strong electrostatic forces between the ions
Are the melting and boiling points of ionic compounds high or low and why?
low because of the weak inter-molecular forces between the molecules
Are the melting and boiling points of covalent (simple molecular) compounds high or low and why?
only when molten or dissolved, not when solid
Do ionic compounds conduct electricity?
Do covalent compounds conduct electricity?
Which element are diamond and graphite made from?
How many bonds does each atom form in graphite?
How many bonds does each atom form in diamond?
large molecules containing chains of carbon atoms
What do simple polymers consist of?
Give an example of a polymer
they are malleable and can conduct electricity
Give two properties of metals
What must be conserved in a chemical reaction?
add up all the relevant relative atomic masses
How can you calculate relative formula mass?
the Avogadro constant number of particles of that substance or a mass of 'relative particle mass' g.