Gases generally have a low density because their molecules are much further apart compared to liquids and solids. In a gaseous state, the molecules possess a lot of kinetic energy, which allows them to move freely and occupy a larger volume. This separation between the molecules results in a lower mass per unit volume, hence a low density.
When we look at the options provided:
- a) Low density: This is correct. Gases have low densities due to the significant distance between their molecules.
- b) High density: This is incorrect. Gases do not have high densities, as mentioned.
- c) No increase in volume when temperature is increased: This is also incorrect. When the temperature of a gas increases, its volume usually increases, according to Charles’s Law.
- d) No decrease in volume when pressure is increased: This is misleading. In fact, gases can decrease in volume under increased pressure due to Gas Laws, often resulting in a contraction of the gas.
In summary, the primary reason gases have low densities is due to the large spaces between their particles, which allows them to expand and fill available space, leading to a lower density compared to other states of matter.