Water is often treated with chlorine,because it

Match List-$I$ with List-$II$ and select the correct answer using the codes given below.

List-$I$	List-$II$
$1.$ Heavy water	$(a)$ Bicarbonates of $Ca$ and $Mg$ in water
$2.$ Temporary hard water	$(b)$ No foreign ions in water
$3.$ Soft water	$(c)$ $D_2O$
$4.$ Permanent hard water	$(d)$ Sulphates and chlorides of $Ca$ and $Mg$ in water

Give an example of a substance that can exist in different physical states. State its physical properties,chemical composition,and characteristics.

Which of the following is not true about the $H_2O$ molecule?

Which of the following is heavy water?

Observe the following statements:
$1.$ Heavy water is harmful for the growth of animals.
$2.$ Heavy water reacts with $Al_4C_3$ and forms $\text{deuterated acetylene}$.
$3.$ $BaCl_2 \cdot 2D_2O$ is an example of $\text{interstitial deuterate}$.
The correct statements are: