HARD
7th CBSE
IMPORTANT
Earn 100
When magnesium burns in air, a white powder is formed. Explain.
Important Questions on Physical and Chemical Changes
HARD
7th CBSE
IMPORTANT
MEDIUM
7th CBSE
IMPORTANT
Frank Everyday Science>Chapter 6 - Physical and Chemical Changes>Let's revise>HOTS Give reasons for the following
MEDIUM
7th CBSE
IMPORTANT
Frank Everyday Science>Chapter 6 - Physical and Chemical Changes>Let's revise>HOTS Give reasons for the following
MEDIUM
7th CBSE
IMPORTANT
Rusting: _____ : : Chemical change: Physical change.
HARD
7th CBSE
IMPORTANT
Copper sulphate: Blue: : Iron sulphate: _____.
MEDIUM
7th CBSE
IMPORTANT
Tin : _____: : Tinning : Galvanising
MEDIUM
7th CBSE
IMPORTANT
Read the passage given below.
A chemical change is one in which changes take place on the molecular level. It produces a new substance whereas a physical change does not produce any new substance. To understand how a physical change occurs, take some sugar crystals and dissolve them in water. The water becomes sweet to taste, which shows that the molecules of sugar are present in water. Evaporate the sugar solution in a china dish over a bunsen burner or a spirit lamp. A white residue is obtained in the china dish. All the properties of this residue are identical to sugar, which was earlier dissolved in water. Thus, we find that in this case no new substance is formed. Hence, dissolving of sugar in water is a physical change.Change in state or phase are physical changes such as melting, freezing, vaporisation, condensation and sublimation. A chemical change results in a substance that was not there before.
Answer the following question by choosing the correct options given below.
In which of the following changes take place at the molecular level?
MEDIUM
7th CBSE
IMPORTANT
A chemical change is one in which changes take place on the molecular level. It produces a new substance whereas a physical change does not produce any new substance. To understand how a physical change occurs, take some sugar crystals and dissolve them in water. The water becomes sweet to taste, which shows that the molecules of sugar are present in water. Evaporate the sugar solution in a china dish over a bunsen burner or a spirit lamp. A white residue is obtained in the china dish. All the properties of this residue are identical to sugar, which was earlier dissolved in water. Thus, we find that in this case no new substance is formed. Hence, dissolving of sugar in water is a physical change.
Change in state or phase are physical changes such as melting, freezing, vaporisation, condensation and sublimation. A chemical change results in a substance that was not there before.
Answer the following question by choosing the correct options given below.
Vaporisation is an example of
