The Nature Of Substances And Chemical Reactions Flashcards
What is an element?
An element is a substance made up of one type of atom and cannot be broken down into anything simpler.
What is a compound?
Give an example.
A compound is a substance that is made of two or more different atoms chemically joined together.
Compounds are made by chemical reactions. During a reaction atoms are rearranged, no atoms are created/destroyed.
E.g burning hydrogen:
2H2 + O2 —> 2H2O
Chemical Symbols and Formulae
Give an example.
Compounds can be represented by chemical formulae. The formula tells you how many of each element is in the compound.
E.g Na2SO4:
2 x Na
1 x S
4 x O
What is the use of a space filler diagram?
Space filler diagrams can be used to show the number of different atoms in molecules.
What is an ion?
Ionic compounds are made from ions. An ion is an atom or molecule that is charged.
Lost electrons and formed positive ions examples.
Na —> Na+ + e-
Mg —> Mg2+ + 2e-
Metals lose electrons to form positive ions.
Gained electrons and formed negative ions examples.
Cl + e- —> Cl-
O + 2e- —> O2-
Non-metals gain electrons to form negative ions.
What are atoms made of?
Protons,neutrons and electrons.
What is the relative atomic mass?
The mass of one element compared to other elements (specifically carbon)
How is the relative molecular mass calculated?
By adding the relative atomic masses of all the atoms in a molecule.
Percentage composition sum?
And example?
(Mass of element / mass of compound) X 100
CH4 = (1 x C / CH4) x 100
= 1 x 12 / 12 + 4 x 100
What is a use of Filtration?
Filtration removes an insoluble solid from a liquid.
What is a use of evaporation when separating mixtures?
Evaporation removes a soluble solid from a liquid.
What is a usage of distillation when separating mixtures?
Distillation separates mixtures of liquids, or removes the solvent from a solution.
What is a usage of chromatography?
Chromatography separates mixtures of dyes or gives information on the compounds in a liquid.
What is chromatography?
Chromatography is used to identify the different compounds present in a liquid.
A drop of the mixture is placed on chromatography paper which is placed in the solvent.
The solvent soaks into the paper and moves upwards.
The dissolved compounds move it different speeds up the paper and so separate out.
