chemical reactions Flashcards
1
Q
physical changes
A
- no new substances formed
- easily reversed
2
Q
chemical changes
A
- one or more new chemical substances formed
- energy is absorbed or released during reactions
- difficult to reverse
3
Q
redox
A
- reduction and oxidation
- chemical reactions where electrons are transferred from one species to another
- always occur together
- used to refer to the loss or gain of oxygen or hydrogen, however it is now known that many redox reactions dont involve oxygen
4
Q
oxidation
A
- loss of electrons
- gain of oxygen
- oxidation state increases
5
Q
reduction
A
- gain of electrons
- loss of oxygen
- oxidation state decreases
6
Q
oxidation states
A
- used to identify redox reactions
- oxidation states indicate how many electrons have been lost, gained or shared when forming a compound
7
Q
elements state
rule 1
A
0
8
Q
group 1
rule 2
A
+1
9
Q
group 2
rule 2
A
+2
10
Q
aluminium
rule 2
A
+3
11
Q
group 7
rule 2
A
-1
12
Q
hydrogen in compound
rule 3
A
+1
13
Q
oxygen in compounds (except peroxides)
rule 4
A
-2
peroxides: -1
14
Q
compound
rule 5
A
sum of each elements oxidation state is 0
15
Q
applications of redox reactions
A
- extraction of metals from their ores
- batteries, using ur phone is oxidation, charging it is reduction
- photosynthesis and respiration
- galvanising and electroplating
