Irreversible Change

Q.

Difference between reversible and irreversible changes

Q. Ripening of fruit is considered to be a chemical change. State the reason.

Q.

A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilized. Can the change in POP be reversed?

Q.

Dissolving sugar in water is an example of ?

Q. Rusting of iron is termed as a permanent change because it:

1. is irreversible
2. is reversible
3. involves the formation of a new substance
4. occurs slowly

Q.

Question 18

Change of a bud into a flower is a change which cannot be reversed. Give four more such example.

Q.

Question 2

Which of the following changes cannot be reversed?
(a) Hardening of cement
(b) Freezing of ice cream
(c) Opening a door
(d) Melting of chocolate

Q.

Paheli mixed flour and water and $\left(\mathrm{i}\right)$ made dough, $\left(\mathrm{ii}\right)$ rolled the dough to make chapati, $\left(\mathrm{iii}\right)$baked the chapati on a pan, $\left(\mathrm{iv}\right)$ dried the chapati and ground it in a grinder to make powder. Identify the changes $\left(\mathrm{i}\right)\mathrm{to}\left(\mathrm{iv}\right)$ as the changes that can be reversed or that cannot be reversed?

Q.

Why does Aluminium metal items which shines like silver when new, turns dull gray after sometime?

1. Chemicals of dish washing brings about a change

2. Dirt sticks quickly to Al metal surface

3. None of the choice

4. Protective layer of $A{l}_2{O}_3$ forms on metal surface

Q.

2. State whether this change can be reversed or not.

(f) Making biogas from cow dung.

Q.

Three substances given below are kept in the open for a few days and some changes were observed.

Which of the substances will show a chemical change?

1. Plastic bottle

2. Eggs

3. Both eggs & moth balls

4. All eggs, plastic bottle and moth balls

Q. Pick the change that can be reversed from the following.

1. Cutting of trees
2. Melting of ghee
3. Burning of candle
4. 
   

   Blooming of a flower

Q. Mention any three changes that take place in our body.

Q.

When baking soda is mixed with lemon juice, bubbles are formed. Which gas is evolved in this reaction?

Q.

Differentiate between a reversible and an irreversible change

Q. Which of the following substance, when mixed with water, undergoes an irreversible change?

1. Sugar
2. Salt
3. Oil
4. Cement

Q.

Name the different types of changes. [1 MARK]

Q.

In an exam, a teacher asked students to give an example of a change which is a physical as well as a chemical change? Which one of the following examples is correct?

1. Photosynthesis

2. Burning of candle

3. Beating of aluminium to make foil

4. Dissolving salt in water

Q. Respected sir
please give me a good answer for my question

clay is moulded into different shapes it is soft .when it is baked it is hard. Is it a chemical change or a physical change? How?

Q.

Question 12

It was Paheli's birthday. Her grandmother gave her two gifts made up of metals, one old dull silver spoon and a pair of lustrous gold ear-rings she was surprised to see the difference in the appearance of the two metals. Can you explain the reason for this difference ?

Q.

This gas is not a constituent of air.

1. hydrogen

2. oxygen

3. carbon dioxide

4. nitrogen

Q. Difference between undiserable changes and discernable changes

Q.

Change of milk to curd is a _______ [desirable/undesirable] change.

Q. Bud to a flower and milk to paneer is a change or not

Q.

Differentiate between physical and chemical change.

Q. Cooking of food : desirable change :: decaying of food : change.

Q.

(B) Classify the following as physical or chemical change.

(vi) Knotting a rope

Q. Which of the following is true for a chemical change?
(I) New substance is formed.
(II) The change is reversible
(III) The change is permanent

1. Only (I) and (II)
2. (I), (II) and (III)
3. Only (I)
4. Only (I) and (III)

Q.

Melting of ice, ageing of living beings, stretching of a rubber band, dissolution of sugar in water

Q.

Nitrogen gas is the most abundantly available gas in the atmosphere.

1. True
2. False