Principles of chemistry - IGCSE Flashcards
Compound
A substance made of two or more types of atoms chemically combined together
Element
A substance made up of only one type of atom
Mixture
Elements that react to form positive metal ions and negatively charged delocalised electrons
Pure substance
A substance which contains only one compound or element.
Pure substances have fixed melting and boiling points
Molecular formula
The actual ratio of atoms of each element present in a compound
Empirical formula
The simplest whole number ratio of atoms of each element in a compound
Period
A row of the periodic table
Elements in the same period have the same number of electron shells
Group
A column on the periodic table
Elements in the same group have similar chemical properties and the same number of valence electrons
Metals
Elements that react to form positive ions
Found to the left and towards the bottom of the periodic table
Non-metals
Elements that react to form negative ions
Found towards the right and top of the periodic table
Noble gases
The elements in group 0 of the periodic table
They have a stable full outer shell of electrons which make them very unreactive
Anion
Negatively charged ion
Cation
Positively charged ion
Electrolysis
The splitting up of an ionic compound using electricity.
The electric current is passed through a substance causing chemical reactions at the electrodes which lead to the decomposition of the materials
Electrode
A solid conductive material through which electricity can flow.
Positive and negative electrodes are used in electrolysis to conduct electricity
Anode
The positive electrode.
Where negatively charged ions lose electrons in oxidation reactions.
Where oxygen is produced unless the solution contains halide ions - then the halogen is produced
Cathode
The negative electrode.
Where positively charged ions gain electrons in reduction reactions.
Where hydrogen is produced if the metal in the electrolyte is more reactive than hydrogen
Oxidation
Reaction involving the gain of oxygen or loss of electroins
Reduction
A reaction involving the loss of oxygen or the gain of electrons
Isotope
Atoms of the same element with the same number of protons but a different number of neutrons
Chromatography
A process used to separate substances in a mixture.
Involves a mobile and a stationary phase.
Paper chromatography
A type of chromatography which uses paper as the stationary phase and a solvent as the mobile phase
The solvent carries the mixture up the paper where the substances in the mixture then separate, depending on how soluble they are in the mobile phase
Mobile phase
The fluid which moves through the chromatography system, carrying the mixture which is to be separated
Stationary phase
The nonmoving phase which the mobile phase passes over during chromatography
Rf value
A value used in chromatography which is calculated as the distance travelled by the dissolved substance divided by the distance travelled by the solvent
It can be used to identify substances within a mixture
Crystallisation
A separation technique to obtain soluble solids form solutions
The process involves heating the solution until crystals start to form, leaving the solution to cool and then filtering the formed crystals from the solution
Filtration
A separation technique used to separate an insoluble solid from a solution
Simple distillation
A separation technique used to separate a liquid from a solution
The solution is heated so that only the liquid with the lowest boiling point evaporates
The gas is then condensed in a condenser before being collected as a liquid
Fractional distillation
A process used to separate a mixture of liquids.
The liquids have different boiling points so they can be separated into different fractions within a fractionating column
Covalent bond
A shared pair of electrons between two non-metals
Giant covalent structure
A molecular structure containing many atoms covalently bonded together
The strong covalent bonds mean that giant covalent strctures have high melting points
Ion
An atom or molecule with an electric charge due to the loss or gain of electrons
Ionic bond
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.
Ionic compound
Chemical compound formed of oppositely charged ions, held together by strong electrostatic forves
Metallic bond
The bonds present in metals between the positive metal ions and negatively charged delocalised electrons
Gas
The state of matter where the particles have the most energy
The particles in a gas are relatively spread out and move randomly in all directions
Liquid
The state of matter where the particles are arranged randomly and close together
The particles are able to move past eachother
Solid
the state of matter where the particles hold a regular arrangement and have the least amount of energy
Solute
A substance which is dissolved in a solvent to create a solution
Solvent
A substance which dissolves a solute
Solution
A homogenous mixture in which a solute is dissolved in a solvent
Saturated solution
A solution which contains the maximum amount of solute that can be dissolved in the solvent.
If any more solute is added, it won’t dissolve in the solution
Solubility
The maximum mass of a solute which can be dissolved in 100g of solvent
Mole
Standard unit for measuring amounts of chemicals
The mole is the unit for amount of substance
Molar volume
The volume occupied by one mole of gaseous molecules
Molar volume at RTP
the volume occupied by one mole of molecules of any gas at room temp and pressure
Molar volume at RTP is 24dm^3
