paper 1 Flashcards
why did mendeleev’s periodic table become more widely accepted? (3 marks)
- he had predicted the properties of missing elements
- elements were discovered
- and the properties of those elements matched his predictions
what are elements in the periodic table arranged in order of?
- increasing atomic number
why did mendeleev reverse order of elements?
- so that they were in groups of similar properties
how does lithium react with water
- a slow reaction
- does not melt
- fizzing can be seen and heard
how does sodium react with water
- large amounts of heat released,
- sodium melts
- hydrogen released catches fire and causes the ball o sodium to move around surface
how does potassium react with water
- burns with a lilac coloured flame
- melts into a shiny ball that dashes around the surface
group one reactions with chlorine
- the chlorine gas disappears
- same as reaction with water
how do group 1 metals react with oxygen
- react to form metal oxides
- metal oxide is a dull coating which covers the surface of the metal
steps to perform a titration for finding the concentration of sulfuric acid, with the known concentration of sodium hydroxide
- 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)
why do carbon nanotubes conduct electricity?
they have a delocalised electron that is free to move and carry charge through the structure
how did alpha particle scattering experiment lead to a change in the model of the atom from the plum pudding model?
- 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
why is the acid gently heated during the making salts experiment?
to speed up the rate of the reaction
advantages of hydrogen fuel cells over a rechargable cell to power cars
- 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)
limitations of particle model
- 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
why is a solid ionic compound not used in electrolysis?
solid ionic compound does not conduct electricity because the ions cannot move in the solid, (can only move in liquid/solution)
why can grpahite conduct electricity?
each carbon atom forms 3 covalent bonds so one electron per carbon is delocalised so these electrons carry charge through the structure.
compare properties of transition and group 1 elements
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
what happens when two atoms of potassium react with one atom of sulfur
- 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
what are the two half equations in a hydrogen fuel cell
H2 → 2H+ + 2e−
O2 + 4H+ + 4e− → 2H2O
how can you get more accurate results of volume
use a pipette or burette to measure volume rather than measuring cylinder as values are more precise
how can you get more accurate results of gas volume
use a gas syringe to collect gas so that the gas would not dissolve in water if using measuring cylinder and water
what is a strong acid
one that fully ionises in aqueous solution or when dissolved in water
how do covalent bonds hold two atoms together
electrostatic forces of attraction between shared pair of negatively charged electrons and positively charged nuclei
what are allotropes
substances made of same element with different structures
describe the structure and bonding of plantium which is a transition metal
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
