GCSE CHEMISTRY INTRODUCTION EXAM REVISION. QUESTIONS
WITH VERIFIED SOLUTIONS LATEST 2025 UPDATE.
Atom - ANSWER- The smallest part of an element that can take place in a chemical reaction
Molecule - ANSWER- a group of atoms held together by covalent bonds
e.g H2 (2 hydrogen atoms bonded together)
What is the molecular structure of an element based on - ANSWER- The amount of electrons
in its outer shell
Chromatography - ANSWER- Method used to separate and distinguishes the different
substances within a mixture
Describe the process of chromatography - ANSWER- 1) Mixture is placed at the end of a strip
of a paper
2) The strip of water is dipped in water
3)As water level rises it takes different dye molecules with it
4) If the ink is a mixture of 2 or more inks different colours will move at different rates allowing
us to identify all the different colours
-Based on how strong the attraction is between the dye molecules and the water
Filtration - ANSWER- Method used to remove undissolved solids from liquids
Describe the process of filtration - ANSWER- 1) Filter paper is folded and put into a funnel
2) Filter allows liquid to flow through but not the solids
3) Results with the solid in the filter paper and the liquid in another container
,Crystillization - ANSWER- Method used to separate dissolved solids from liquids
Describe the process of crystillization - ANSWER- 1)Solution is heated in an open container
2) Solvent evaporates leaving a saturated solution
3) Saturated solution is left to cool where crystals of solid will grow in the solution
4) When the solution has completely evaporated crystallised solids are left
Distillation - ANSWER- Method used to separate a pure liquid from a mixture
Describe the process of distillation - ANSWER- 1) Mixture is heated in a flask
2) At a specific temperature the substance with a lower boiling point will evaporate into vapour
3) The vapour will travel down a condenser filled with cool running water cooling it back down a
liquid
4) As it travels down the condensor it will be collected in a separate container leaving the other
liquid in the flask
Fractional distillation - ANSWER- Method to separate a liquid mixture into its individual
components
Describe the process of fractional distillation - ANSWER- 1) Mixture is heated and different
substances evaporate at different time based on their boiling point
2)Different substance condense at different portions of the fractionating column (The higher up,
the lower the temperature)
3)Each substance will travel down a different condensor and get collected in different containers
Describe the importance of purity in substances - ANSWER- Impurities in drugs or foods can
be hazardous and detrimental to our health
,How to test for purity in a substance - ANSWER- Check if the substance boils/melts at a distinct
point, if it doesnt the substance isnt pure
Chemical substance - ANSWER- When a substance combines with another to form a new
substance
eg. Rotting fruit
Mixing chemicals
-Irreversible
Physical change - ANSWER- Changes that affect the form of an object but has no affect on its
chemical composition
eg. Tearing a piece of tin foil
Crumpling a paper
-Reversible
-No new substance is formed
Mixture - ANSWER- A system of 2 or more substances that are not chemically combined and
can be separated by physical means
Element - ANSWER- A substance which cannot be divided into simpler substances by chemical
means; all atoms in a element have the same number of protons
Compounds - ANSWER- Substances formed by the chemical combination of 2 or more
chemical elements in fixed proportions
What is an atom made up of? - ANSWER- Subatomic particles
-Neutrons
-Protons
, -Electrons
Nucleus - ANSWER- Central region of an atom that is made of the protons and neutrons in the
atom
Electron orbitals - ANSWER- Electron orbiting the nucleus
Describe the electron arrangement - ANSWER- Electrons are arranged in shells
-Each shell is equivalent to an energy level
First shell: 2 electrons
Second shell: 8 electrons
Third shell: 8 electrons
Proton properties - ANSWER- Relative mass: 1
Relative charge: +1
Electron properties - ANSWER- Relative mass: 1/1836
Relative charge: -1
Neutron properties - ANSWER- Relative mass: 1
Relative charge: 0
What happens when you go across the period by one - ANSWER- Atom will have one more
proton than the previous element
Isotope - ANSWER- Atoms of the same element which have a different neutron number but
the same proton number
WITH VERIFIED SOLUTIONS LATEST 2025 UPDATE.
Atom - ANSWER- The smallest part of an element that can take place in a chemical reaction
Molecule - ANSWER- a group of atoms held together by covalent bonds
e.g H2 (2 hydrogen atoms bonded together)
What is the molecular structure of an element based on - ANSWER- The amount of electrons
in its outer shell
Chromatography - ANSWER- Method used to separate and distinguishes the different
substances within a mixture
Describe the process of chromatography - ANSWER- 1) Mixture is placed at the end of a strip
of a paper
2) The strip of water is dipped in water
3)As water level rises it takes different dye molecules with it
4) If the ink is a mixture of 2 or more inks different colours will move at different rates allowing
us to identify all the different colours
-Based on how strong the attraction is between the dye molecules and the water
Filtration - ANSWER- Method used to remove undissolved solids from liquids
Describe the process of filtration - ANSWER- 1) Filter paper is folded and put into a funnel
2) Filter allows liquid to flow through but not the solids
3) Results with the solid in the filter paper and the liquid in another container
,Crystillization - ANSWER- Method used to separate dissolved solids from liquids
Describe the process of crystillization - ANSWER- 1)Solution is heated in an open container
2) Solvent evaporates leaving a saturated solution
3) Saturated solution is left to cool where crystals of solid will grow in the solution
4) When the solution has completely evaporated crystallised solids are left
Distillation - ANSWER- Method used to separate a pure liquid from a mixture
Describe the process of distillation - ANSWER- 1) Mixture is heated in a flask
2) At a specific temperature the substance with a lower boiling point will evaporate into vapour
3) The vapour will travel down a condenser filled with cool running water cooling it back down a
liquid
4) As it travels down the condensor it will be collected in a separate container leaving the other
liquid in the flask
Fractional distillation - ANSWER- Method to separate a liquid mixture into its individual
components
Describe the process of fractional distillation - ANSWER- 1) Mixture is heated and different
substances evaporate at different time based on their boiling point
2)Different substance condense at different portions of the fractionating column (The higher up,
the lower the temperature)
3)Each substance will travel down a different condensor and get collected in different containers
Describe the importance of purity in substances - ANSWER- Impurities in drugs or foods can
be hazardous and detrimental to our health
,How to test for purity in a substance - ANSWER- Check if the substance boils/melts at a distinct
point, if it doesnt the substance isnt pure
Chemical substance - ANSWER- When a substance combines with another to form a new
substance
eg. Rotting fruit
Mixing chemicals
-Irreversible
Physical change - ANSWER- Changes that affect the form of an object but has no affect on its
chemical composition
eg. Tearing a piece of tin foil
Crumpling a paper
-Reversible
-No new substance is formed
Mixture - ANSWER- A system of 2 or more substances that are not chemically combined and
can be separated by physical means
Element - ANSWER- A substance which cannot be divided into simpler substances by chemical
means; all atoms in a element have the same number of protons
Compounds - ANSWER- Substances formed by the chemical combination of 2 or more
chemical elements in fixed proportions
What is an atom made up of? - ANSWER- Subatomic particles
-Neutrons
-Protons
, -Electrons
Nucleus - ANSWER- Central region of an atom that is made of the protons and neutrons in the
atom
Electron orbitals - ANSWER- Electron orbiting the nucleus
Describe the electron arrangement - ANSWER- Electrons are arranged in shells
-Each shell is equivalent to an energy level
First shell: 2 electrons
Second shell: 8 electrons
Third shell: 8 electrons
Proton properties - ANSWER- Relative mass: 1
Relative charge: +1
Electron properties - ANSWER- Relative mass: 1/1836
Relative charge: -1
Neutron properties - ANSWER- Relative mass: 1
Relative charge: 0
What happens when you go across the period by one - ANSWER- Atom will have one more
proton than the previous element
Isotope - ANSWER- Atoms of the same element which have a different neutron number but
the same proton number
