WJEC Chemistry GCSE Definitions
and Concepts, GCSE Edexcel
Chemistry - Key Concepts in
chemistry;<Chem Quest>.
Bulk properties - ANSWER The properties such as strength, melting point,
conductivity, flexibility and hardness which are related to the different types of bonds
the compound contains, the bond strengths in relation to intermolecular forces and
the ways in which the bonds are arranged. The atoms themselves do not have these
properties.
Conductor - ANSWER A material that contains charged particles which are free to
move to carry electrical or thermal energy. Metals are good conductors due to the
delocalised electrons.
Covalent bond - ANSWER A shared pair of electrons between two non-metals.
Diamond - ANSWER A giant covalent structure which is made up of carbon atoms
each of which form four covalent bonds with four other carbon atoms. The structure
makes diamond very hard, making it suitable for use as drill bits.
Electrostatic forces - ANSWER The strong forces of attraction between oppositely
charged ions.
Fullerenes - ANSWER Molecules of carbon atoms with hollow shapes. The
structures are based on hexagonal rings of carbon atoms but they may also contain
rings with five or seven carbon atoms. Examples include graphene and C60.
Giant covalent structure - ANSWER A molecular structure containing many atoms
covalently bonded together. The strong covalent bonds mean that giant covalent
structures have high melting points.
Graphene - ANSWER A single layer of graphite with properties that make it useful
in electronics and composites.
Graphite - ANSWER A giant covalent structure which is made up of carbon atoms
each of which form three covalent bonds with three other carbon atoms. These
atoms form layers of hexagonal rings which have no covalent bonds between them.
There is one delocalised electron per carbon atom which is free to move to carry
charge.
Ion - ANSWER An atom or molecule with an electric charge due to the loss or gain
of electrons. A positive ion is formed when an atom loses electrons, and a negative
ion is formed when an atom gains electrons.
Ionic bond - ANSWER The bond formed between the oppositely charged ions when
a metal atom loses electron(s) to form a positively charged ion and a non-metal
gains these electron(s) to form a negatively charged ion.
, WJEC Chemistry GCSE Definitions
and Concepts, GCSE Edexcel
Chemistry - Key Concepts in
chemistry;<Chem Quest>.
Ionic compound - ANSWER Chemical compound formed of oppositely charged
ions, held together by strong electrostatic forces.
Lattice - ANSWER A repeating regular arrangement of atoms/ions/molecules. This
arrangement occurs in crystal structures.
Malleable - ANSWER Capable of being deformed and moulded into various
shapes. Metals are malleable since the uniform layers of atoms can slide over each
other.
Metallic bond - ANSWER The bonds present in metals between the positive metal
ions and negatively charged delocalised electrons.
Nanoparticles - ANSWER Particles with diameters between 1 nm to 100 nm in size.
Nanoparticles can exhibit properties different to those for the same material in bulk.
Simple molecules - ANSWER Molecules containing a fixed number of atoms
covalently bonded together. Simple molecules have low boiling points since they
have weak intermolecular forces which are easy to overcome.
Smart materials - ANSWER Materials which respond to certain external stimuli
such as temperature and moisture.
Acid - ANSWER Produces hydrogen ions (H+) in aqueous solutions with a pH
range between 0 and 7. Acids will react with metals to produce a salt and hydrogen
and will react with carbonates to produce a salt, water and carbon dioxide.
Alkali - ANSWER Produces hydroxide ions (OH-) in aqueous solutions with a pH
range between 7 and 14. Alkalis are water soluble bases.
Neutralisation - ANSWER The reaction in which an acid and a base react together
to form a salt and water. Generally, neutralisation reactions are reactions in which
hydrogen ions react with hydroxide ions to form water: H+ + OH- → H2O.
pH scale - ANSWER A measure of the acidity or alkalinity of a solution. The scale
ranges from 0-14 and can be measured using universal indicator or a pH probe.
Precipitation reaction - ANSWER A reaction in which solutions react to form an
insoluble product.
Strong acid - ANSWER An acid which is completely ionised in an aqueous solution
so that nearly all the H+ ions are released. Examples of strong acids include
hydrochloric, nitric and sulfuric acids.
and Concepts, GCSE Edexcel
Chemistry - Key Concepts in
chemistry;<Chem Quest>.
Bulk properties - ANSWER The properties such as strength, melting point,
conductivity, flexibility and hardness which are related to the different types of bonds
the compound contains, the bond strengths in relation to intermolecular forces and
the ways in which the bonds are arranged. The atoms themselves do not have these
properties.
Conductor - ANSWER A material that contains charged particles which are free to
move to carry electrical or thermal energy. Metals are good conductors due to the
delocalised electrons.
Covalent bond - ANSWER A shared pair of electrons between two non-metals.
Diamond - ANSWER A giant covalent structure which is made up of carbon atoms
each of which form four covalent bonds with four other carbon atoms. The structure
makes diamond very hard, making it suitable for use as drill bits.
Electrostatic forces - ANSWER The strong forces of attraction between oppositely
charged ions.
Fullerenes - ANSWER Molecules of carbon atoms with hollow shapes. The
structures are based on hexagonal rings of carbon atoms but they may also contain
rings with five or seven carbon atoms. Examples include graphene and C60.
Giant covalent structure - ANSWER A molecular structure containing many atoms
covalently bonded together. The strong covalent bonds mean that giant covalent
structures have high melting points.
Graphene - ANSWER A single layer of graphite with properties that make it useful
in electronics and composites.
Graphite - ANSWER A giant covalent structure which is made up of carbon atoms
each of which form three covalent bonds with three other carbon atoms. These
atoms form layers of hexagonal rings which have no covalent bonds between them.
There is one delocalised electron per carbon atom which is free to move to carry
charge.
Ion - ANSWER An atom or molecule with an electric charge due to the loss or gain
of electrons. A positive ion is formed when an atom loses electrons, and a negative
ion is formed when an atom gains electrons.
Ionic bond - ANSWER The bond formed between the oppositely charged ions when
a metal atom loses electron(s) to form a positively charged ion and a non-metal
gains these electron(s) to form a negatively charged ion.
, WJEC Chemistry GCSE Definitions
and Concepts, GCSE Edexcel
Chemistry - Key Concepts in
chemistry;<Chem Quest>.
Ionic compound - ANSWER Chemical compound formed of oppositely charged
ions, held together by strong electrostatic forces.
Lattice - ANSWER A repeating regular arrangement of atoms/ions/molecules. This
arrangement occurs in crystal structures.
Malleable - ANSWER Capable of being deformed and moulded into various
shapes. Metals are malleable since the uniform layers of atoms can slide over each
other.
Metallic bond - ANSWER The bonds present in metals between the positive metal
ions and negatively charged delocalised electrons.
Nanoparticles - ANSWER Particles with diameters between 1 nm to 100 nm in size.
Nanoparticles can exhibit properties different to those for the same material in bulk.
Simple molecules - ANSWER Molecules containing a fixed number of atoms
covalently bonded together. Simple molecules have low boiling points since they
have weak intermolecular forces which are easy to overcome.
Smart materials - ANSWER Materials which respond to certain external stimuli
such as temperature and moisture.
Acid - ANSWER Produces hydrogen ions (H+) in aqueous solutions with a pH
range between 0 and 7. Acids will react with metals to produce a salt and hydrogen
and will react with carbonates to produce a salt, water and carbon dioxide.
Alkali - ANSWER Produces hydroxide ions (OH-) in aqueous solutions with a pH
range between 7 and 14. Alkalis are water soluble bases.
Neutralisation - ANSWER The reaction in which an acid and a base react together
to form a salt and water. Generally, neutralisation reactions are reactions in which
hydrogen ions react with hydroxide ions to form water: H+ + OH- → H2O.
pH scale - ANSWER A measure of the acidity or alkalinity of a solution. The scale
ranges from 0-14 and can be measured using universal indicator or a pH probe.
Precipitation reaction - ANSWER A reaction in which solutions react to form an
insoluble product.
Strong acid - ANSWER An acid which is completely ionised in an aqueous solution
so that nearly all the H+ ions are released. Examples of strong acids include
hydrochloric, nitric and sulfuric acids.
