CHEMICAL COMPOSITION - Coggle Diagram
All matter around us, including you and me, are made of elements
Most elements are found chemically combined with other elements, existing as compounds. Elements, such as gold, silver, carbon, nitrogen, oxygen, helium can be found naturally as uncombined elements.
An element is a pure substance which cannot be broken down into two or more simpler substances by chemical reactions.
Atoms are the smallest particles of an element that have the chemical properties of that element.
An element is made up of only one type of atom.
High boiling points
High melting points
Malleable and ductile
Shiny solids, except mercury (liquid)
Good conductors of electricity
Good conductors of thermal energy
Low boiling points
Low melting points
Dull solids, liquids or gases (except diamond)
Poor conductors of electricity except carbon (graphite)
Poor conductors of thermal energy
Malleable: Can be flattened by sheets
Ductile: Can be drawn into wires
Brittle: Breaks easily into pieces
Sonorous: Produces a ringing sound when hit
Metalloids exhibit both metallic and non-metallic properties. E.g. silicon resembles metals, has a grey metallic sheen and very high melting and boiling points. Yet, it is brittle just like solid non-metals. Unlike metals and non-metals, it is a semiconductor.
A molecule is a group of identical atoms chemically combined together
The chemical formula of a molecule shows the types and numbers of atoms contained in it.
A compound is a pure substance which consists of two or more elements chemically combined together
The properties of compounds are different from teh properties of its constituent elements.
The elements that make up a compound are always combined in a fixed proportion by mass.
Compounds can only be broken down into simpler substances by chemical reactions such as heating and electrolysis.
Compounds are formed by chemical reactions.
A mixture consists of two or more different substances (elements or compounds) that are mixed, but not chemically combined.
A mixture has similar properties as the substances that it is made of
The components that make up a mixture are not present in a fixed proportion by mass
Mixtures can be separated into pure substances by physical methods such as filtration and evaporation.
When mixtures are formed, no chemical reaction takes place.
A few non-metallic elements exist as atoms such as helium and neon.
Metallic elements generally exist as atoms
Non-metallic elements generally exists as molecules.
Elements, Compounds and Mixtures
A pure substance only consists of one type of substance.
A pure substance melts or boils sharply at a specific melting point and boiling point.
An impure substance consists of more than one type of substance.
A mixture/impure substance melts or boils over a range of temperatures
For most substances, the presence of an impurity increases its boiling point but decreases its melting point.
COMPOUNDS VS ELEMENTS
Made up of two or more types of atoms
Can be broken down into two or more simpler substances
Made up of one type of atoms only
Cannot be broken down into any simpler substances
COMPOUNDS VS MIXTURES
Pure. Made up of two or more elements chemically combined
Elements in a compound are combined in a fixed proportion by mass
Melts or boils at a fixed melting point and boiling point
Chemical reaction takes place during its formation
Has different properties from its constituent elements
Can only be separated by chemical reactions like heat and electrolysis
Impure. Made up of two or more substances not chemically combined
Components that make up a mixture are not present in a fixed proportion by mass.
Melts or boils over a range of temperatures
No chemical reaction takes place during its formation
Has similar properties as the substances that it's made up of
Can be separated by physical methods such as filtration and evaporation
SOLUTIONS AND SUSPENSIONS
A solution is a homogeneous mixture formed when a soluble solute is dissolved in a solvent
Solute: The substance that dissolves in a solvent, e.g. salt
Solvent: The substance that dissolves the solute, e.g. water
Solution: The mixture of the solute and the solvent, e.g. saltwater
A suspension is a heterogeneous mixture formed when an insoluble solute is suspended in a solvent (liquid or gas). The solid is unevenly distributed in a liquid and it has to be stirred and shaken to get a uniformity in it.
Solid particles in a suspension do not dissolve, and can be seen in the suspension.
When a suspension is filtered, teh solid particles are too large to pass through filter paper. Hence, they are left behind as a residue on the filter paper.
When a suspension is left to stand for some time, the solid particles settle to the bottom.
SOLUBILITY AND RATE OF DISSOLVING
Solubility is the maximum mass of solute that can dissolve in 100g of solvent at a fiver temperature
Type of solvent: Salt dissolves in water, but does not dissolve in oil.
Type of the solute: Sugar dissolves in water, but oil does not dissolve in water.
Temperature: Sugar dissolves in hot water but not in cold water
RATE OF DISSOLVING:
The rate of dissolving is a measure of how fast a fixed amount of substance dissolves in a fixed volume of solvent, given a fixed amount of time.
Temperature: The higher the solvent's temperature, the faster the dissolving rate.
Surface area of solute: The smaller the size of the solute particles, the faster the solute dissolves, because smaller particles have larger surface area in contact with solvent.
Rate of stirring: The faster the rate of stirring, the faster the solute dissolves.