Question:
Fill in the blanks in the following statements:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _____.
(b) The chemical name of baking soda is _.
(c) Two methods by which rusting of iron can be prevented are _ and _.
(d) Changes in which only _ properties of a substance change re called physical changes.
(e) Changes in which new substances are formed are called _____ changes.

Answer:

(a) Calcium carbonate (CaCO₃)
CO₂ that is Carbon dioxide reacts with Ca(OH)₂ (Calcium hydroxide) that is lime water, to form a white precipitate of CaCO₃ (Calcium carbonate).

(b) Sodium hydrogen carbonate
The chemical name of baking soda is (NaHCO₃) Sodium hydrogen carbonate (Sodium bicarbonate) .Sodium bicarbonate comes with sodium, acid and hydrogen. Sodium carbonate is diprotic and a strong base compound.

(c) Painting and galvanization Metals which cannot wear easily are melted into their molten form and are used to cover metals which rust easily. The surface of iron or metal are coated with paint or grease. Galvanization is the process of applying a protective layer of zinc on a metal. It is a very common method of preventing the rusting of iron.

(d) Physical
The change in which physical properties of the substance or a material change, this is called physical change. In physical changes, no new substances are formed.

(e) Chemical
The changes in which cannot be seen by naked eyes are called chemical changes. The chemical changes cannot be reversed.

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