Which of the following statements is incorrect about physical changes?a)There is no gain or loss of energy.b)It is permanent and irreversible.c)Composition of the substance remains same.d)No new substance is formed.Correct answer is option 'B'. Can you explain this answer?

Question

Answer

Explanation:

Physical changes are changes in the physical properties of a substance, such as shape, size, state, or appearance. They do not involve any change in the chemical composition of the substance. Some common examples of physical changes are melting, freezing, boiling, condensation, sublimation, and dissolution.

Now, let us analyze the given statements one by one:

a) There is no gain or loss of energy: This statement is correct. Physical changes do not involve any change in the energy of the substance. The energy may be required to carry out the change, but it is not gained or lost by the substance itself.

b) It is permanent and irreversible: This statement is incorrect. Physical changes are usually temporary and reversible. For example, if we melt an ice cube, it will turn into water, but we can freeze the water again to get back the ice cube. Similarly, if we dissolve salt in water, we can evaporate the water to get back the salt.

c) Composition of the substance remains the same: This statement is correct. Physical changes do not involve any change in the chemical composition of the substance. The atoms or molecules of the substance remain the same before and after the change.

d) No new substance is formed: This statement is correct. Physical changes do not involve any chemical reaction, so no new substance is formed. The substance may change its state or appearance, but it remains the same substance.

Therefore, the correct answer is option 'B' which says that physical changes are permanent and irreversible. In reality, physical changes are usually temporary and reversible.

Answer

B is correct as physical changes can be reversed

Answer

Physical change can be reversed in it's original form so it is temporary not permanent and not irreversible.

Answer

In a physical change, no new substance is formed. The change is temporary and can be easily reversed. There is no change in mass of the substance as there is a change in its form and not in the bulk. There is no loss or gain of energy because the exact same amount of energy is released back during the reverse process.

Answer

Answer
is option b)It is permanent and irreversible

Let me explain to you what is physical change

Physical change is the change where
the physical properties like shape, size, etc. of a substance are only changed.
It does not alter the chemical properties of the substance and no new substance
is formed.

I hope you have understood what physical change is, now let me explain
each of the options given in the question.

Option a)There is no
gain and loss of energy

This statement is correct. The reason is that in order for the substance
to lose or gain energy a new substance should be formed from the substance.

Option b)It is
permanent and irreversible

This statement is incorrect. Physical changes are usually reversible. For
example, if we freeze water it will change into its solid state that is ice.
Now if we melt ice it would change its state to liquid that is water.

Option c)Composition
of the substance remains same

This statement is correct. As I have explained earlier, a physical
change will only change the physical properties of a substance not the chemical
properties or composition.

Option d)No new substance
is formed

The statement is correct. As I have already explained earlier no new substance
is formed when a physical change happens.

But if you ask, 'If we mix salt in water it will form a salt
solution, right? So isn't it a new substance and is a chemical change'

Well I guess, you are right. I won't go deep into the topic but i will
explain to you a little bit. Salt dissolving in water is usually considered to
be a physical change however the chemical species in salt solution (hydrated
sodium and chlorine ions) are different from the species in solid salt.

But one thing you should know even though some textbooks say that
chemical changes are irreversible and physical changes are reversible, it is
wrong, although reversing chemical change can be difficult to do. For example
cutting paper is a physical change but it is irreversible. Rechargeable
batteries use one chemical reaction when discharging and recharging involves
driving that reaction backwards, turning the products back into the original
reactants.

But
if a question in your school exam comes like “Is dissolving salt in water a
chemical change or physical change?” write according to what your book has
explained, just for the sake of getting full marks.

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