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Observations of Chemical Changes

Which of the ...

Question

Which of the following changes indicate that a chemical change has not been taken place?

A

No new substance is formed

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B

Absorption or release of heat

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C

Change in colour

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D

Evolution of gas

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Solution

The correct option is A No new substance is formed
A chemical change is a permanent change in which new substances are formed that are entirely different from the original substance.
It is usually accompanied by:
$∙$ change in colour
$∙$ formation of new substances
$∙$ evolution of gas
$∙$ release or absorption of energy in the form of heat or light or sound, etc.

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Similar questions

Which of the following observations helps to determine whether a chemical reaction has taken place or not?

(i) Change in state.

(ii) Change in colour.

(iii) Change in shape

(iv) Evolution of gas.

(v) Change in temperature.

Q. Which of the following observation does not indicate a chemical change has occurred?

Q. Matter undergoes a change. The changes are of two types: Physical and chemical change.

A physical change is a change that involves only a change in the physical state of matter. Its chemical properties remain the same. Usually increasing the temperature or applying pressure or both bring about a physical change. On reversing the condition, that is reducing the temperature or reducing the pressure or both, the original state of matter is restored. In other words, physical changes are reversible.

A chemical change is a change that involves a change in the chemical composition of matter. A new substance is formed. In a chemical change, new chemical and physical properties of the substance are formed. In a chemical change, the chemical and physical properties of the substance formed will be different from the original substance.

In a chemical change, the properties that change are :

Q. Following are the observations of changes that have taken place. Classify them into chemical change or a physical change. [5 MARKS]

1. The change is temporary and can be reversed by changing the conditions in most of the cases.
2. New substance(s) is/are formed.
3. The chemical properties of the original substance remain the same.
4. There is an exchange of energy during this change which means that heat and light may be given out or absorbed.
5. As a result of the change, there may or may not be any change in the energy possessed by the original substance.
6. There is no change in the chemical composition of the original substance.
7. The change is permanent and cannot be reversed by changing the conditions or through ordinary physical processes.
8. There may or may not be any change in the state, size, shape, colour, and smell of the substance that undergoes this change.
9. The composition and the properties of the parent substance or substances change.
10. There is usually a change in the mass of the parent substance/s as well.

Q. The following are the observations of changes that have taken place. Align them to either chemical change or a physical change.

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