(Q.1) classify the changes involved in the following process as a physical or a chemical changes:
a) photosynthesis
b) dissolving sugar in water
c) burning of a coal
d) melting of a wax
e) beating aluminium to make aluminium foil
f) digestion of food
Answers
Answer:
ANSWER
Physical changes only lead to changes in physical properties of the substance and are reversible chemical changes lead to change in composition or the structure and are irreversible in nature.
(a) Photosynthesis: irreversible, chemical changes.
6CO
2
+6H
2
O⟶C
6
H
12
O
6
+6O
2
(b) Dissolving of water : reversible, physical change.
(c) Bumping of coal − irreversible, chemical change.
(d) Melting of wax − reversible by cooling, physical change.
(e) Physical change as mallacbility (beating metal into then sheets) does not change composition.
(f) Digestion − chemical change.
Answer
a) Photosynthesis ➝ Chemical Change
- Because here energy is generated by absorbing carbondioxide & water in the presence of sunlight, and gives out energy, oxygen and water
b) Dissolving Sugar in water ➝ Physical Change
- We can reverse the reaction. The salt and water can be seperated back by simple Evaporation
c) Burning of cola ➝ Chemical Change
- We can't change back the burnt coal back to its original form, if it was possible then we won't have to dig the coal from the underground and instead just burn and convert them back
d) Melting of wax ➝ Physical Change
- Melting of wax is a Physical Change as the melted wax cools back and returns to its initial stage. But burning of wax is a chemical change
e) Beating of aluminium to make aluminium foil ➝ Physical Change
- The beaten aluminium foil can be reversed back to its earlier stage by simply melting and cooling it
f) Digestion of food ➝ Chemical Change
- In the process of digestion the food gets digested to give out. energy and after it gets digested we can't turn them back to their own original State
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