5 — elements, compounds and mixtures Flashcards
Element
An element is a pure substance that cannot be broken down into 2 or more simpler substances by chemical methods
Metalloids
Elements that have properties of both metals and non-metals
Compound
A compound is a pure substance containing 2 or more different elements that r chemically combined in a fixed ratio
Separation of chemical compounds into constituent elements
- Thermal decomposition
- Electrolysis
Molecule
A molecule is a group of 2 or more non-metal atoms that r chemically combined tgt
(Can be atoms of same or different elements)
2 atoms chemically combined: diatomic molecules
3 or more atoms chemically combined: polyatomic molecules
Mixture
A mixture is made up of 2 or more elements and/or compounds that r not chemically combined
Explain if x is a compound or a mixture
It is a mixture since x is made up of y number of compounds and are not chemical combined tgt.
Composition of elements, compounds and mixtures (avoid using definitions to compare)
Formation:
E: mostly natural occurring
C: from a chemical reaction
M:usually from physical mixing
Ratio of its constituents
E: -
C: fixed ratio
M: no fixed ratio
Properties
E: -
C: dif properties from its constituent elements
M: similar properties to its constituent substances
Melting and boiling points
E: fixed
C: fixed
M:melt and boil over a range of temperatures
Energy
E: -
C: a chem reaction takes place when a compound is formed — usually has an energy change
M: no chem reaction takes place when a mixture is formed — usually no or little energy change
Separation:
E: -
C: chemical methods
M: physical methods