GCSE AQA Chemistry 2025
What are all substances made of? - ANS- Atoms which are the smallest part of an
element that can exist.
What is the size of an atom and nucleus? - ANS- Atoms radius is 1x10^-10 m. The
nucleus is 1/10,000 of the atom.
How to calculate the number of protons, electrons and neutrons when given atomic
number and mass number - ANS- The atomic number is the top number, mass number
bottom.
Number of protons is atomic number. Number of electrons is atomic number. Number of
neutrons is mass number - atomic number.
How to name an ionic compound - ANS- Metals element symbol first, non-metal takes
the name ending 'ide' unless oxygen is present. When oxygen is present, use the ending
'ate'. The ending 'ite' has less oxygen than 'ate'.
How to name a covalent compound - ANS- They are named using prefixes (mono, di, tri,
tetra, penta) to show how many of each element is present in the formula.
Which covalent compound names are you expected to know? - ANS- H2SO4 - Sulfuric
Acid
NH3 - Ammonia
CH4 - Methane
HCl - Hydrochloric Acid
C2H5OH - Ethanol
HNO3 - Nitric Acid
What is a physical method? - ANS- A method that doesn't involve a chemical reaction,
so doesn't form any new substances
How is filtration and crystallisation used to separate rock salt? - ANS- Rock Salt is a
mixture of salt and sand.
1 - GRIND the mixture to make sure the salt crystals are small so will dissolve easily.
2 - Put the mixture in water and stir. The salt will DISSOLVE but the sand won't.
3 - FILTER the mixture. The grains of sand won't fit through the tiny holes in the filter
paper, so they collect on the paper instead. The salt passes through the filter paper as it
is part of the solution.
4 - EVAPORATE the water from the salt so that it forms dry crystals.
, What are the 2 benefits of fractional column? - ANS- Hotter at the bottom, cooler at the
top
Bigger surface area.
Order of when subatomic structures were found - ANS- Electron - J.J Thompson 1987
Nucleus - Ernest Rutherford 1911
Proton - Ernest Rutherford 1917
Neutrons - James Chadwick 1932
What is the plum pudding model of the atom? - ANS- The atom is a ball of positive
charge with negative electrons embedded into it.
Compare Plum Pudding model with the nuclear model of the atom - ANS- Atom is mostly
positively charged in PPM, atom is mostly empty space in NM
Negative electrons are distributed throughout the atom in PPM, negative electrons orbit
the nucleus at a distance
Mass of the atom is evenly distributed in PPM, almost all of the mass of the atom is
concentrated in the positively charged nucleus
Alpha scattering experiment conclusions - ANS- Most of the alpha particles went straight
through the gold foil because most of the atom is empty space.
Some of the atoms deflected (went a different direction) as the nucleus of the atom must
have a positive charge which repels the nucleus of the alpha particles.
A few of the alpha particles bounced straight back because the mass of the atom must be
concentrated in the centre.
Why did the alpha scattering experiment lead to a new model of the atom? - ANS-
Because the results shown in the alpha scattering experiment did not match the
properties of the PPM.
The nuclear model different to the PPM, concluded that the mass of the atom is
concentrated in the centre in the nucleus. Also, the nucleus is positively charged.
Atoms radius - ANS- 0.1 nm (1 x 10-10 m)
Nucleus radius - ANS- 1 x 10-14 m
It is less than 1/10,000 size of an atom.
What is the top and bottom number of an element? - ANS- Top number is mass number
and bottom number is atomic number.
What are all substances made of? - ANS- Atoms which are the smallest part of an
element that can exist.
What is the size of an atom and nucleus? - ANS- Atoms radius is 1x10^-10 m. The
nucleus is 1/10,000 of the atom.
How to calculate the number of protons, electrons and neutrons when given atomic
number and mass number - ANS- The atomic number is the top number, mass number
bottom.
Number of protons is atomic number. Number of electrons is atomic number. Number of
neutrons is mass number - atomic number.
How to name an ionic compound - ANS- Metals element symbol first, non-metal takes
the name ending 'ide' unless oxygen is present. When oxygen is present, use the ending
'ate'. The ending 'ite' has less oxygen than 'ate'.
How to name a covalent compound - ANS- They are named using prefixes (mono, di, tri,
tetra, penta) to show how many of each element is present in the formula.
Which covalent compound names are you expected to know? - ANS- H2SO4 - Sulfuric
Acid
NH3 - Ammonia
CH4 - Methane
HCl - Hydrochloric Acid
C2H5OH - Ethanol
HNO3 - Nitric Acid
What is a physical method? - ANS- A method that doesn't involve a chemical reaction,
so doesn't form any new substances
How is filtration and crystallisation used to separate rock salt? - ANS- Rock Salt is a
mixture of salt and sand.
1 - GRIND the mixture to make sure the salt crystals are small so will dissolve easily.
2 - Put the mixture in water and stir. The salt will DISSOLVE but the sand won't.
3 - FILTER the mixture. The grains of sand won't fit through the tiny holes in the filter
paper, so they collect on the paper instead. The salt passes through the filter paper as it
is part of the solution.
4 - EVAPORATE the water from the salt so that it forms dry crystals.
, What are the 2 benefits of fractional column? - ANS- Hotter at the bottom, cooler at the
top
Bigger surface area.
Order of when subatomic structures were found - ANS- Electron - J.J Thompson 1987
Nucleus - Ernest Rutherford 1911
Proton - Ernest Rutherford 1917
Neutrons - James Chadwick 1932
What is the plum pudding model of the atom? - ANS- The atom is a ball of positive
charge with negative electrons embedded into it.
Compare Plum Pudding model with the nuclear model of the atom - ANS- Atom is mostly
positively charged in PPM, atom is mostly empty space in NM
Negative electrons are distributed throughout the atom in PPM, negative electrons orbit
the nucleus at a distance
Mass of the atom is evenly distributed in PPM, almost all of the mass of the atom is
concentrated in the positively charged nucleus
Alpha scattering experiment conclusions - ANS- Most of the alpha particles went straight
through the gold foil because most of the atom is empty space.
Some of the atoms deflected (went a different direction) as the nucleus of the atom must
have a positive charge which repels the nucleus of the alpha particles.
A few of the alpha particles bounced straight back because the mass of the atom must be
concentrated in the centre.
Why did the alpha scattering experiment lead to a new model of the atom? - ANS-
Because the results shown in the alpha scattering experiment did not match the
properties of the PPM.
The nuclear model different to the PPM, concluded that the mass of the atom is
concentrated in the centre in the nucleus. Also, the nucleus is positively charged.
Atoms radius - ANS- 0.1 nm (1 x 10-10 m)
Nucleus radius - ANS- 1 x 10-14 m
It is less than 1/10,000 size of an atom.
What is the top and bottom number of an element? - ANS- Top number is mass number
and bottom number is atomic number.
