Atoms, Elements, Compounds & Mixtures
Pure substances are made up of one type of atom |
Atoms of the same element are exactly alike |
Atoms cannot be created, destroyed, or divided into smaller particles |
An element is a pure substance that cannot decompose into simpler substances |
Compounds are formed by joining 2 or more elements e.g. water; they can be broken down into simpler substances |
Mixtures are two are more elements or compounds which are not chemically combined |
Mixtures can be homogeneous (uniform) e.g. sugar + water or heterogeneous (non-uniform) dirt + water |
Physical Separation Techniques
SEPARATING SOLIDS |
Sieving (density) |
Separating solid particles according to particle size by passing them through a perforated barrier |
Sedimentation |
Process in which solids settle to the bottom of a container |
SEPARATING SOLIDS FROM LIQUIDS |
Filtration (solubility, particle sizes) |
Process of separating undissolved solid from a liquid or gas by passing the mixture through a filter |
Decanting |
Process of carefully pouring out the liquid and leaving the solid undisturbed at the bottom of the container |
SEPARATING DISSOLVED SOLIDS AND LIQUIDS |
Evaporation (boiling point) |
Process of separating a dissolved solid from a solution by vaporising the liquid |
Crystallisation |
Process of forming crystals from a solution |
SEPARATING LIQUIDS |
Separating funnel (miscibility) |
Placing mixture in a separating funnel and opening the tap to let out the lower layer into a clean vessel below |
Distillation (boiling point) |
Process of separating the liquid by boiling the solution and condensing the resulting vapour back to a liquid (big difference in boiling points) |
SEPARATING GASES |
Fractional Distillation |
Similar to distillation, but performed under colder conditions instead of at room temperature (small difference in boiling points) |
OTHER SEPARATION METHODS |
Centrifugation |
Process of spinning molecules with different densities around an axis at high speed |
Magnetic Separation (magnetism) |
Process of passing a mixture through a magnetic field to separate the magnetic field and non-magnetic components |
Chromatography |
Process whereby mixture is dissolved in a solvent (called the mobile phase), which carries it through a second substance called the stationary phase |
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Atoms
An atom is the smallest particle of an element that is still recognisable as that element |
Atoms are made up of three sub atomic particles: electrons (-1), protons (+1) and neutrons (0) |
An atom consists of an extremely small, dense, and positively charged nucleus or core, which contains the bulk of the mass of the atom |
This nucleus is surrounded by an electron cloud of rapidly moving and extremely light negatively charged particles (electrons). |
Atomic number, Z, of an element is the number of protons in the nucleus of an atom of that element. |
The mass number, A, is the number of protons plus neutrons in the nucleus of an atom |
Number of electrons in the electron cloud is equal to the number of protons in the nucleus |
Table of Transition Metal and Metal Cations:
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Naming Inorganic Compounds
There are two types of inorganic compounds that can be formed: ionic compounds and molecular compounds. |
COMPOUNDS BETWEEN METALS AND NON-METALS |
When an atom loses one or more electrons, it becomes a positively-charged ion (cations) |
The cation (metal) is always named first with its name unchanged |
When an atom gains one or more electrons, it becomes a negatively-charged ion (anions) |
The anion (non-metal) is written after the cation, modified to end in –ide |
Transition metals may form more than one ion |
Example of Compounds Between Metals and Non-metals
More Than One Ion Example
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