All matter is made up of the five elements. Hence, to understand the five elements at a deeper level, it is useful to know their qualities.
Air is the principle of motion and hence it is responsible for all movement. Air is mobile; all other elements are inherently static, as they have no inherent internal source of motion. Static relates most closely to earth. Earth is the most stable and it takes the most energy to move it. All elements can move, however their motion is dependent upon air, as air it the source of all motion. The ether and fire elements are often stated in texts to be mobile as well. However, their motion is still motivated by air. Ether and fire provide virtually no resistance to air. Hence, they are not at all stable, yet they have no inherent motion and so are inherently static. It is best to look at ether and fire as unstable, water and earth as most stable and air alone as mobile.
Dull, or resistant, as in a dull mind, relates to the water and earth elements. Sharp, or penetrating, relates to fire, air and ether. The sharp quality can be most easily understood as a quality of the voice or of the words a person chooses. A sharp voice and a sharp tongue are characteristic of Pitta and Vata. A sharp mind is another Pitta characteristic. A dull mind is a Kapha characteristic. Sharp increases Pitta and Vata. Dull increases Kapha.
Soft is a quality of water. On the emotional level, softness is related to compassion, love, and tenderness. These are qualities generally associated with a person of Kapha nature. Hardness relates to all the other elements. When air or fire causes dryness, the resulting substance becomes hard. Earth is inherently hard. Ether is neither hard not soft. Vata dosha is increases by the quality of hardness and decreased by the quality of softness. Kapha dosha is increased by softness and decreased by hardness. This is true in spite of the fact that Kapha contains earth. The large amount of water element inherent within Kapha creates softness. Pitta, which contains fire and water, is interesting in that it has a unique interaction with the qualities of hardness and softness. When Pitta is balanced, it contains significant water and as such it is soft. As it increases, the fire dries out the water. If Pitta remains increased for long periods, the result is hardness of the body and mind.
Like soft, smooth relates to water. Water makes rocks smooth as it flows over them. Water increases the smoothness of whatever it is in contact with. Rough is related to hard and dry substances. Earth is considered rough, as it is hard and dry. Fire increases roughness if it burns hot for very long, as it will increases dryness and hardness. Air, like the wind, causes out skin to become rough, dry and hard. Hence, air, fire and earth are rough. Water is smooth. Ether is neither rough nor smooth. Smooth increases Kapha. Rough increases Vata. The oily nature of Kapha is increased by smooth and rough increases the fiery nature of Pitta.
Clear is a quality of fire, air and ether. Fire burns away obstructions leaving a channel clear. Fire purifies what it comes into contact with. Air scrapes away obstructions. Air also purifies. Ether is inherently clear, being purity itself. A clear mind is one that is unencumbered by heaviness and lethargy. Clear is associated with purity and the purification process increases clarity. Water and earth are cloudy. They are understood to be so because they are not purifying and do not increase the quality of lightness. They are heavy and nourishing elements. Cloudy increases Kapha. Clear, or clarity, increases Pitta and Vata.