Explanation:
Chemical Reaction: A chemical reaction is the change that brings about new products.
Chemical Change:
- Chemical changes produce new substances.
- Most chemical changes are irreversible.
- Chemical changes are product-oriented.
- Chemical changes follow the law of conservation of mass.
Physical Change:
- Physical changes are reversible.
- No new substance is formed in a physical change.
- Physical changes involve changes in the state of matter.
Important Points
- Melting of ice results in water, which can be frozen back to ice, thus it is a physical change.
- Crystallization is a process that changes liquids into solids, which is again a physical change.
- Souring of milk is a chemical change because a new substance, yogurt, is formed.
- Dissolving sugar in water is the formation of a solution that can be called a mixture.
- There is no reaction in the mixture of sugar and water, so it is a physical change.
Additional Information
Temperature: It is the degree of amount of heat and cold measured.
Boiling Point: The minimum temperature at which a liquid starts to boil is called its boiling point.
Freezing Point: The minimum temperature at which a liquid starts to freeze is called the freezing point.
Melting Point: The minimum temperature at which a solid starts to melt or changes into a liquid is called the melting point.
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Important Questions from Basic Concepts of Chemistry
Which of the following pair is correct?
I. Isotopes – different mass numbers
II. Isobars – different atomic numbers
Which of the following is a zone of a flame?
I. Dark
II. Luminous
III. Non-Luminous
Sphalerite is an ore of:
If formula of sodium salt of an anion X is \(Na_2X\) , then the formula of its aluminium salt would be
Which of the following set contains same number of molecules?
A. 1 gram O 2, 2 grams SO 2
B. 1 gram CO 2, 1 gram N 2O
C. 1 gram O 2, 1 gram O 3
