Q21
2 marksVery Short AnswerSection B

A student performs the following experiment in his school laboratory. List two observations to justify that in this experiment a chemical change has taken place.

Figure for question 21
Chemical Reactions and Equations
Chemical Reactions
Official Answer

Two observations to justify that in this experiment a chemical change has taken place are: 1. The color of the solution changes from colorless to yellow. 2. The solution becomes hot.

chemical changecolor changetemperature change

Marking Scheme

  • 1Observation 1: Color change from colorless to yellow
  • 2Observation 2: Solution becomes hot

Hint

Look for changes in color, temperature, or other physical properties that indicate a chemical reaction has occurred.

Quick Oral Answer

A chemical change has taken place in this experiment because the color of the solution changes from colorless to yellow, and the solution becomes hot. These observations indicate that a chemical reaction has occurred, resulting in the formation of a new substance with different properties.

Analysis & Explanation

The question requires the student to analyze the experiment and identify two observations that justify a chemical change has taken place. The correct answer is based on the principles of chemical reactions and the characteristics of chemical changes.

Common Mistakes

  1. 1Confusing physical changes with chemical changes
  2. 2Not considering all possible observations

Interesting Facts

Chemical reactions can result in changes in color, temperature, or other physical properties.

Chemical reactions involve the breaking and forming of chemical bonds.

Spotted a mistake or something unclear?

Tell us — we fix reported answers fast.

Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2025?

This question carries 2 marks in the CBSE Class 10 Science 2025 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 "Chemical Reactions" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2025 paper?

This is a Very Short Answer question from Section B in the CBSE Class 10 Science 2025 paper.