eoy prep

Question 1

how has the model of an atom changed over time?

Question 2

describe the structure of an atom

Answer 2

an atom is made up of a nucleus containing protons and neutrons, surrounded by electrons in shells. most of an atom is empty space, as a nucleus is quite small, and electrons are even smaller.

Question 3

where is most of the mass of an atom found

Answer 3

the nucleus

Question 4

what is the relative charge and mass of a proton, neutron, and electron

Answer 4

proton:
charge = +1
mass = 1
neutron:
charge = 0
mass = 1
electron:
charge = -1
mass = 1/1835 (negligible)

Question 5

what is the atomic number

Answer 5

the number of protons in an element

Question 6

what is the difference between the mass number and the relative atomic mass of an element

Answer 6

the mass number is the sum of the protons and neutrons in a particular atom - this will always be a whole number.
the relative atomic mass of an element is the weighted average mass of all the isotopes of the element - it will most likely not be an integer.

Question 7

what is an isotope

Answer 7

an isotope is an atom of an element with a different number of neutrons to another atom of the same element

Question 8

what is an ion

Answer 8

an ion is an atom of an element that has gained or lost electrons to have a full outer shell. metals usually lose electrons (cations), while non-metals gain electrons (anions).

Question 9

what is the formula to calculate the relative atomic mass (Ar) of an element

Answer 9

Ar=(isotope 1’s mass number * its percentage abundance in the total group of atoms) + (isotope 2’s mass number * its percentage abundance in the total group of atoms) etc./100

Question 10

what is the collective name for elements in group one and why

Answer 10

alkali metals, because they are all very reactive (they react on contact with water), and they all have one electron in their outer shell

Question 11

what is the collective name for elements in group two and why

Answer 11

alkaline earth metals, because they are reactive with water (hence ‘alkaline’) and their oxides are found in the earth’s crust. as well as this, they all have two electrons in their outer shell

Question 12

what are the transition metals

Answer 12

the elements found in the central block of the periodic table between group two and three.

Question 13

what is the collective name for elements in group seven and why

Answer 13

halogens, because they are all very reactive non-metals (as well as being extremely poisonous). they also all have seven electrons in their outer shell.

Question 14

what is the collective name for elements in group zero/eight and why

Answer 14

noble gases, because they are incredibly unreactive (some don’t react to anything at all, such as neon). this is due to their full outer shell, meaning they are naturally stable (they don’t have to become ions to be stable).

Question 15

where is the line between metals and non-metals on the periodic table

Answer 15

known as the steps to boron, the line between metals and non-metals is a zigzag from astatine to boron, with metals on the left and non-metals on the right. this is also dictated by the elements’ atomic structure, in that metals lose electrons to form cations, whereas non-metals gain electrons to form anions. as well as this, metals usually have 1-4 valence electrons, whilst non-metals have 4-8.

Question 16

explain how the electronic configuration of an element is related to its position in the periodic table

Answer 16

the electronic configuration of an element determines its exact position in the periodic table. the group number of the element is given by how many electrons the element has in its outer shell, and the period is given by the number of shells of electrons there are in the element (when it is not an ion). for the transition metals, their position is decided by how many electrons they have, as each element has one more electron than the element to its left.

Question 17

what is the difference between the use of ‘pure’ in chemistry compared with its everyday use

Answer 17

in chemistry, a pure substance is a substance that only contains one element, such as distilled water. however, in everyday use, one might advertise a drink as pure orange juice, but that does not mean it is only made of orange juice atoms.

Question 17

how can you interpret melting point data to distinguish between pure substances and mixtures

Answer 17

pure substances have a sharp melting point, whereas mixtures will melt over a range of temperatures due to the different elements involved.

Question 17

what is filtration used for, and how is it done

Answer 17

separating an insoluble solid from a liquid. the liquid filtrate passes through the filter paper, leaving the undissolved solid residue on the paper.

Question 18

what is evaporation used for, and how is it done

Answer 18

separating a soluble solid from a solution. the solution is heated, allowing the solvent to evaporate, leaving the solid solute behind.

Question 19

what is a solvent

Answer 19

the liquid in a solution

Question 20

what is a solute

Answer 20

the solid in a solution

Question 21

what are all the diatomic elements

Question 22

what is crystallisation used for, and how is it done

Answer 22

separating a soluble solid (solute) from a solution, usually to make crystals from a solution where the solvent is water. the solution is put in a warm place and left to evaporate slowly. when it becomes saturated crystals form, which can be separated from any remaining solution by filtration. the crystals contain water in their structure, so if strong heating was used on them the water would evaporate away, leaving an anhydrous powder.

Question 23

what does anhydrous mean

Answer 23

a substance that contains no water.

Question 24

what is simple distillation used for, and how is it done

Answer 24

separating a solvent from a solution. simple distillation relies on vastly different boiling points of the individual pure components in the solution. the solution is heated and the solvent evaporates into a tube surrounded by a cooling jacket (another tube, filled with cold running water). here, the solvent condenses to a liquid, and then falls into a separate container. the other liquid becomes more concentrated, as the amount of solvent decreases.

Question 25

what is fractional distillation used for, and how is it done

Answer 25

separating miscible liquids. fractional distillation is used when the boiling points of the two liquids are similar, so it uses a fractionating column. the mixture is boiled, and the vapours of both liquids pass into the column, but there is a higher proportion of the substance with the lower boiling point (the more volatile one). in the fractionating column, they condense and reboil many times, each time with a higher proportion of the more volatile liquid (as it is able to reboil faster). as a result, the liquid with the lower boiling point emerges in a pure state at the top of the column first, and passes into the container. a thermometer is used to measure the boiling point of the liquid distilling over at any moment.

Question 26

what does miscible mean (and its opposite)

Answer 26

the term given when two liquids can mix with each other (eg. alcohol and water) as opposed to being immiscible (eg. oil and water)

Question 27

what is the difference between simple and fractional distillation

Answer 27

simple distillation is used to separate a solution with elements/compounds that have drastically different boiling points, whilst fractional distillation is used to separate a solution with elements/compounds that have similar boiling points. it also uses a fractionating column.

Question 28

what is a separating funnel used for, and how is it used

Answer 28

separating a mixture of immiscible liquids. when the mixture is poured into the funnel, the less dense liquid (eg. oil) will sit on top, and the more dense liquid (eg. water) will stay on the bottom, with a clear line between the two. therefore, you can simply collect the liquids in two separate beakers by opening and closing the tap correctly.