5.1.1.1 Atoms, Elements and Compounds Flashcards
1
Q
What are all substances made of?
A
- atoms
2
Q
What is an atom?
A
- smallest part of an element that can exist
3
Q
How are atoms of each element represented?
A
- by a chemical symbol
- e.g. O represents an atom of oxygen
- e.g. Na represents an atom of sodium
4
Q
How many different elements are there?
A
- 100+
5
Q
How are elements shown?
A
- in the periodic table
6
Q
How are compounds formed?
A
- from elements by chemical reactions
7
Q
What do chemical reactions always involve?
A
- formation of one or more new substances
- often involve a detectable energy change
8
Q
What do compounds contain?
A
- two or more elements chemically combined in fixed proportions
9
Q
How can compounds be represented?
A
- formulae using the symbols of the atoms from which they were formed
10
Q
How can compounds be separated into elements?
A
- chemical reactions
11
Q
How can chemical reactions be represented?
A
- word equations
- equations using symbols and formulae
