paper 1

Question 1

why did mendeleev’s periodic table become more widely accepted? (3 marks)

Answer 1

• he had predicted the properties of missing elements
• elements were discovered
• and the properties of those elements matched his predictions

Question 2

what are elements in the periodic table arranged in order of?

Answer 2

• increasing atomic number

Question 3

why did mendeleev reverse order of elements?

Answer 3

• so that they were in groups of similar properties

Question 4

how does lithium react with water

Answer 4

• a slow reaction
• does not melt
• fizzing can be seen and heard

Question 5

how does sodium react with water

Answer 5

• large amounts of heat released,
• sodium melts
• hydrogen released catches fire and causes the ball o sodium to move around surface

Question 6

how does potassium react with water

Answer 6

• burns with a lilac coloured flame
• melts into a shiny ball that dashes around the surface

Question 7

group one reactions with chlorine

Answer 7

• the chlorine gas disappears
• same as reaction with water

Question 8

how do group 1 metals react with oxygen

Answer 8

• react to form metal oxides
• metal oxide is a dull coating which covers the surface of the metal

Question 9

steps to perform a titration for finding the concentration of sulfuric acid, with the known concentration of sodium hydroxide

Answer 9

• use a pipette to measure the fixed volume of sulfuric acid and transfer it to a conical flask
• add a few drops of indicator to the acid - if using phenolphthalein then it should be colourless
• place conical flask on a white tile so colour change is more visible
• set up a burette above the conical flask, attached to a clamp
• add a fixed concentration of sodium hydroxide
• perform a rough titration to find the approximate end point
• record the volume of sodium hydroxide used
• repeat the experiment to remove anomolies and calculate a mean (when calculating mean use concordant results)

Question 10

why do carbon nanotubes conduct electricity?

Answer 10

they have a delocalised electron that is free to move and carry charge through the structure

Question 11

how did alpha particle scattering experiment lead to a change in the model of the atom from the plum pudding model?

Answer 11

• most of the particles passed straight through so it was mainly empty space, and mass was concentrated at the centre
• some deflected therefore the atom is positively charged at the nucleus

Question 12

why is the acid gently heated during the making salts experiment?

Answer 12

to speed up the rate of the reaction

Question 13

advantages of hydrogen fuel cells over a rechargable cell to power cars

Answer 13

• no toxic chemicals to dispose of at the end of the cell’s life
• take less time to refuel (than to recharge rechargeable cells)
• travel further before refuelling (than before recharging
  rechargeable cells)
• no loss of efficiency (over time)

Question 14

limitations of particle model

Answer 14

• particles are shown as spheres
• its only 2d
• doesnt show the movement or speed of the particles
• doesnt show the weak forces between the particles

Question 15

why is a solid ionic compound not used in electrolysis?

Answer 15

solid ionic compound does not conduct electricity because the ions cannot move in the solid, (can only move in liquid/solution)

Question 16

why can grpahite conduct electricity?

Answer 16

each carbon atom forms 3 covalent bonds so one electron per carbon is delocalised so these electrons carry charge through the structure.

Question 17

compare properties of transition and group 1 elements

Answer 17

Physical:
Transition elements
- high melting points
- high densities
- strong
- hard
Group 1
- low melting points
- low densities
- soft

Chemical:
Transition elements
- low reactivity/react slowly (with water or oxygen)
- used as catalysts
- ions with different charges
- coloured compounds
Group 1
- very reactive/react (quickly) with water/non-metals
- not used as catalysts
- white/colourless compounds
- only forms a +1 ion

Question 18

what happens when two atoms of potassium react with one atom of sulfur

Answer 18

• electrons transferred from potassium to sulfur
• two potassium atoms each lose one electron
• forming K+ / 1+ ions
• sulfur atoms gain 2 electrons
• forming S2- / 2- ions

Question 19

what are the two half equations in a hydrogen fuel cell

Answer 19

H2 → 2H+ + 2e−

O2 + 4H+ + 4e− → 2H2O

Question 20

how can you get more accurate results of volume

Answer 20

use a pipette or burette to measure volume rather than measuring cylinder as values are more precise

Question 21

how can you get more accurate results of gas volume

Answer 21

use a gas syringe to collect gas so that the gas would not dissolve in water if using measuring cylinder and water

Question 22

what is a strong acid

Answer 22

one that fully ionises in aqueous solution or when dissolved in water

Question 23

how do covalent bonds hold two atoms together

Answer 23

electrostatic forces of attraction between shared pair of negatively charged electrons and positively charged nuclei

Question 24

what are allotropes

Answer 24

substances made of same element with different structures

Question 25

describe the structure and bonding of plantium which is a transition metal

Answer 25

it is a giand structure with a sea of delocalised electrons. the positive metal ions and electrons are held together by strong electrostatic forces of attraction