LONGER ANSWERS PAPER 1 Flashcards
Explain why the reactivity of elements changes going down Group 1.
- reactivity increases
- as outer electron is further from the nucleus
- there is less attraction between the nucleus and the outer electron
- so the atom loses an electron more easily
Explain why alloys are harder than pure metals
- in an alloy the atoms are of different sizes
- so the layers of atoms are distorted
- so in an alloy the layers slide over each other less easily
Explain the trend in boiling points of the halogens as you go down the group
- boiling point increases down the group
- because the size of the molecule increases
- so the intermolecular forces increase in strength
- so more energy is needed to overcome the intermolecular forces
Explain why the reactivity of the halogens decreases going down the group.
- going down the group the outer electrons become further from the nucleus
- so the nucleus has less attraction for the outer electrons
- so an electron is gained less easily
Explain why ammonia has a low boiling point.
- ammonia has small molecules / a simple molecular structure
- ammonia has weak intermolecular forces
-so little energy is needed to overcome the intermolecular forces
Explain why hydrogen chloride is a gas at room temperature
- hydrogen chloride is made of small molecules / is simple molecular structure
- so hydrogen chloride has weak intermolecular forces
- intermolecular forces require little energy to overcome
Explain why this alloy is harder than the pure metal
- the atoms / particles / ions are different sizes
- so there are no layers to slide
Potassium forms an ionic compound with sulfur.
Describe what happens when two atoms of potassium react with one atom of sulfur. Potassium has 1 electron and sulfur has 6.
- electrons transferred from potassium to sulfur
- two potassium atoms each lose one electron, forming K 1+ ions
- sulfur atoms gain 2 electrons forming S 2− ions
Explain why graphite is:
* a good electrical conductor
* soft and slippery.
- bonds are covalent
- giant / macromolecular structure
- three(covalent bonds per carbon atom
- so one electron per carbon atom is delocalised, they can move through the structure carrying charge
- so graphite conducts electricity
- layered structure of hexagonal rings
- with weak intermolecular forces between layers
- so the layers can slide over each other
- so graphite is soft and slippery
Suggest why it is cheaper to use nanoparticles of silver rather than coarse particles of silver
- nano particles have a larger surface area to volume ratio
- so less can be used for the same effect
Explain why diamond is hard.
- it is a giant structure
- that has strong covalent bonds
Explain why thermosetting polymers are better than thermosoftening polymers for saucepan handles.
- thermosetting polymers do not melt when heated
- due to cross-links between chains
Evidence from the alpha particle scattering experiment led to a change in
the model of the atom from the plum pudding model.
- most alpha particles passed straight through the gold foil
- so the mass of the atom is concentrated in the nucleus and most of the atom is empty space
- some alpha particles were deflected / reflected
- so the atom has a positively charged nucleus
Chadwick’s experimental work on the atom led to a better understanding of
isotopes.
Explain how his work led to this understanding.
- Chadwick provided the evidence to show the existence of neutrons
- this was necessary because isotopes have the same number of protons
- but with different numbers of neutrons
Compare the plum pudding model with the nuclear model of the atom.
SIMILARITIES
* both have positive charges
* both have negative electrons
* neither has neutrons
DIFFERENCES
plum pudding model:
- ball of positive charge spread
throughout
- electrons are embedded in the ball of positive charge
- no empty space in the atom
- mass spread throughout
nuclear model:
- positive charge concentrated at
the centre
- electrons outside the nucleus
- most of the atom is empty space
- mass concentrated at the centre
what are the physical properties of transition elements?
- high melting points
- high densities
- strong
- hard
what are the physical properties of group 1 metals?
- low melting points
- low densities
- soft
what are the chemical properties of transition elements?
- low reactivity / react slowly (with water or oxygen)
- used as catalysts
- ions with different charges
- coloured compounds
what are the chemical properties of group 1 elements?
- very reactive / react (quickly) with water / non-metals
- not used as catalysts
- white / colourless compounds
- only forms a +1 ion
explain the properties of ionic compounds
- have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds
- When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
explain the properties of small molecules
- have only weak intermolecular forces between the molecules. It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.
- The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
- These substances do not conduct electricity because the molecules do not have an overall electric charge.
describe and explain the properties of graphene
- good conductor of electricity; delocalised electrons are free to move and carry charge
- strong
- high MP/BP; high number of covalent bonds which require a lot of energy to break
describe the electrolysis of aluminium oxide
- aluminium oxide is mixed with cyolite lowers the melting point
- reduces the amount of energy needed and saves money
- the cathode and anode are both make of graphite (carbon)
- the Al3+ ions are attracted to the negative electrode (cathode). each ion gains 3 electrons and forms an aluminium atom. Al3+ + 3e- -> Al
- the O2- ions are attracted to the positive electrode (anode). each ion loses 2 electrons to form an oxygen atom. 2O2- -> O2 + 4e-
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