Water: Properties and States of Matter - Class IX

Law of Constant proportion states that a chemical compound always contains same elements combined together in the same proportion by mass.

When hydrogen and oxygen combine to form water, they form water an extremely stable compound. We can say water is a stable compound because tremendous energy is released is a signal that hydrogen and oxygen are very eager to become water or in another way it is very hard to break water molecules apart into its components.

Hydrogen combines with oxygen to form water. Water exists in solid ( ice), liquid ( water) and gas ( water vapor).

Natural water, such as that found in rivers and lakes, contains dissolved gases like oxygen (essential for aquatic life) and carbon dioxide (from the atmosphere and respiration).

This law states that all samples of a given chemical compound have the same elemental composition by mass e.g. oxygen makes 8/9th of the mass of pure water while hydrogen makes up the remaining 1/9th of the mass.

The law of definite proportions and constant composition states that all samples of a given chemical compound have the same elemental composition by mass e.g. oxygen makes up up about 8/9th of mass of any sample of pure water while hydrogen makes up the remaining 1/9th of mass.

All of the following statements are correct for the composition of water.
A
For water, the gravimetric or mass ratio of hydrogen to oxygen is 1:8.
B
In water, the ratio of hydrogen and oxygen is 2:1 by volume.
C
The ratio in which hydrogen and oxygen combine gives the composition of water.
Note:
$2H _2 + O _2 \rightarrow 2H _2O$
Thus, the composition of water is $H : O = 2: 1 $
It is the ratio in which hydrogen and oxygen combine. The atomic masses of H and O are 1 and 16 respectively. Hence, for water, the gravimetric or mass ratio of hydrogen to oxygen is 2:16 or 1:8.
In water, the ratio of hydrogen and oxygen is 2:1
by volume. It is equal to the ratio in which hydrogen and oxygen combine.

Water will start comparing electrostatically,

According to the law of constant composition in a given compound, the elements always combine in the same proportion as each other.

The water vapor rises in the atmosphere due to heating of water by sunlight and there it cools down and forms tiny water droplets through something called condensation. When they all combine together, they grow bigger and are too heavy to stay up there in the air. This is when they will fall to the ground as rain, or maybe snow or hail by gravity.

The evaporation takes place at all the time

Condensation is the process by which water vapor in the air is changed into liquid water.Cloud formation is caused by condensation of water vapor in the atmosphere condensing into a liquid state. Thus Option C is correct.

The process of changing water vapour into water is called condensation.

Evaporation causes cooling.

Evaporation is the process of a liquid converts into gaseous phase. In all these process liquid moles are evaporated into gaseous phase. Hence, option D is correct.

Wet clothes dry in sun due to evaporation the water in wet clothes takes heat energy from sun and gets evaporated.This process involves evaporation.
Hence, option A is correct.

Drying clothes is an example of evaporation as in evaporation water evaporates by the heat of the sun thus helping in drying of clothes .

Evaporation of the substance is the process in which the substance transition from liquid phase to gas phase. Condensation is the process in which gas returns to liquid form. Hence, options A is correct.

                            	<span class="ng-binding">The fog appeared on sun glasses when gets in front of hot steam due to condensation.Condensation is the process where the vapor converts into liquid.<br>Hence option A is correct.<br></span>

                            	<span class="ng-binding">Evaporation

is the process of a liquid converts into gaseous phase.In all these
process liquid moles are evaporated into gaseous phase.So all the above processes involves evoporation.
Hence option D is correct.

The formation of water droplets on cold soda can while having soda in summer season is due to the process of condensation.

Condensation is the process where a gaseous substance converts into liquid.
Ex: Rainfall.