NCERT 6th Class (CBSE) Science: Changes Around Us

Question: When sugar dissolves in water, it disappears. That means it must have change into a new substance. Therefore, dissolving is a chemical change. Do you agree?

Answer: 

1. Sugar remains sugar and water remains water.
2. Properties are same and do not changed.
3. They can be separated by crystallization.

Question: On boiling potato becomes soft and egg becomes hard. What value do you barn?

Answer: On boiling the potato becomes soft and egg becomes hard through both of them undergone through the same situation but they reacted differently. We barn that it’s the person’s character not the circumstances that determine that he will be successful or not.

Question: Give two examples of slow changes.

Answer:

1.  Growing of plants
2.  Ripening of fruits.

Question: Give two examples of fast changes.

Answer:

1.  Blowing of balloon
2.  Rolling out roti from dough ball.

Question: Give two examples of reversible changes.

Answer:

1.  Drying of wet clothes
2.  Heating of milk.

Question: Give two examples of irreversible changes.

Answer:

1. Milk to cheese
2. Cooking of food.

Question: Can you say deforestation is an irreversible or reversible change?

Answer: It is an irreversible change.

Question: Why does a blacksmith heat the metal rim to fix it on a cart wheel?

Answer: A blacksmith heats the metal rim to fix it onto a cart wheel because a metal rim is made slightly smaller. On heating, the rim expands and fits onto the wheel. Then on cooling, the rim contracts and fits tightly onto the wheel.