In which of the following, the identity of initial substance remains unchanged?
In which of the following, the identity of initial substance remains unchanged?
Options
Official answer
The correct option is B.
Marking scheme
- 1.1 mark for selecting the correct option (B).
Hint
Identify which of the given processes is a physical change where no new chemical substance is formed.
Quick oral answer
Crystallisation is a physical change because it only changes the physical form of the substance into highly ordered crystals without altering its chemical composition or forming any new substance.
Common mistakes
- 1.Students may confuse biological or organic processes like fermentation and digestion as physical changes, but they involve complex chemical breakdowns.
Analysis and explanation
According to the NCERT text, whenever a chemical change occurs, a chemical reaction takes place, and the nature and identity of the initial substance change. Curdling of milk, fermentation of grapes, and digestion of food are all chemical changes where new substances are formed, changing the identity of the starting materials. In contrast, the formation of crystals by the process of crystallisation is a physical change. During crystallisation, only the physical state and arrangement of particles change to form pure crystals, while the chemical identity of the substance remains completely unchanged.
Interesting facts
Crystallisation is a highly effective purification technique used in industries to obtain pure solids (like sugar or salt) from their impure solutions without altering their chemical properties.
Question details
Q10 of 30 questions
- Board
- CBSE
- Class
- Class 10
- Subject
- Science
- Year
- 2020
- Section
- Section A
- Marks
- 1
- Type
- MCQ
- Chapter
- Chemical Reactions and Equations
- Topic
- Physical and Chemical Changes
- Bloom's level
- Understanding
- Syllabus topic
- Chemical reactions: Chemical equation, Balanced chemical equation, implications of a balanced chemical equation, type of chemical reactions
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Frequently asked questions
How many marks does this question carry in CBSE Class 10 Science 2020?
This question carries 1 mark in the CBSE Class 10 Science 2020 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Physical and Chemical Changes" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2020 paper?
This is a MCQ question from Section A in the CBSE Class 10 Science 2020 paper.