Useful Definitions Flashcards
What is an element?
A substance that is only made up from one type of atom
What is an atom?
The smallest part of an element that can take part in a chemical reaction
What is a molecule?
The smallest particle of a compound/elements that are diatomic
What is an ion?
The name given to any electrically charged atom or molecule
- positively charged ions are called cations
- negatively charged ions are called anions
What is accuracy?
How CLOSE values are to the ACCEPTED VALUE
What is activation energy?
The minimum amount of energy that colliding particles need for a reaction to occur
What is atomic number?
The number of protons in the nucleus of an element
Avogadro’s law
Equal volumes of gases under the same conditions of temperature and pressure contain the same number of molecules
What are basic oxides?
Oxides of metals that react with water to form metal hydroxides and with acids to form salts and water
What is bond enthalpy?
The enthalpy change when one mole of a bond in the gaseous state is broken
What is bond length?
The distance between nuclei of two atoms that are covalently bonded together
What is a catalyst?
A substance that increases the rate of a chemical reaction but is chemically unchanged at the end of the reaction
What is cracking?
The breakdown of molecules into shorter ones by heating with a catalyst
What are delocalised electrons?
Electrons that are not associated with any single atom or covalent bond
What is disproportionation?
When an element is both oxidised and reduced in the same reaction
What is electronegativity?
The ability of an atom to attract a bonding pair of electrons
What is an electrophile?
- A species that is attracted to a region of high electron density
- Electron acceptor
What is the end point?
The point at which the indicator just changes colour
What does endothermic mean?
Heat energy is transferred from the soundings to the system
What is the equivalence point?
The point at which there are exactly the right amounts of substances to complete the reaction
What is an error?
The different between an experimental value and the accepted value
What is an ethanolic solution?
A solution where ethanol is used as the solvent
What does exothermic mean?
Heat energy is transferred from the system to the surroundings
What is first ionisation energy?
The energy required to remove an electron from each atom in one mole of gaseous atoms
What is second ionisation energy?
The energy required to remove a electron from each singly charged positive ion in one mole of positively charged ions in the gaseous state
What is Hess’ law?
The enthalpy change of a reaction is independent of the route taken
What is a hetrogeneous catalyst?
A catalyst that is in a different phase to that of the reactants
What is hetrolytic fission?
The breaking of a covalent bond so that both bonding electrons are taken by one atom
What is a heterogeneous system?
A system where there at least two different phases are present
What is homolytic fission?
The breaking of a covalent bond where each of the bonding electrons leaves with one species, forming a radical
What does Hund’s rule state?
Electrons will occupy the orbitals singly before electron pairing takes place
What is a hydrogen bond?
- An intermolecular interaction between a hydrogen atom and an atom which is more electronegative than hydrogen
- this would normally be between fluorine, oxygen and nitrogen atoms
What is a locant?
A number used to indicate which carbon atom in an chain an atom or group is attached to
What is mean bond enthalpy?
The average enthalpy change when one mole of a bond is broken
What is a measurement uncertainty?
The potential error involved when using a piece of apparatus to make a measurement
What is a meniscus?
The curving of the upper surface in a liquid in a container
What is metallic bonding?
The electrostatic force of attraction between the nuclei of positively charged metal ions and delocalised electrons
What is molar concentration?
The amount (in mol) of a solute divided by the volume of the solution
What is a mole?
The amount of a substance that contains the same number of particles as the number of carbon atoms in exactly 12g of carbon-12
What is the molecular ion peak?
The peak with the highest m/z ratio in the mass spectrum
What are monomers?
Small molecules that combine to form a polymer
