Structure and potential of water.

Question 1

Density of water

Answer 1

The density of water is nearly 1 g/cm3 at 4°C. When the temperature of water is different from 4°C, higher or lower than 4°C, the density of pure water is less than 1 g/cm3.

Question 2

Viscosity

Answer 2

It is defined as the ratio of the drag force and the velocity gradient perpendicular to the direction of flow. The reciprocal of viscosity is known as fluidity.

Question 3

Specific heat capacity

Answer 3

The specific heat capacity of a substance is defined as the amount of heat required to change the temperature of a unit mass of a substance by a unit degree.

Question 4

Cohesion

Answer 4

The attraction of water molecules for each other is known as cohesion.

Question 5

Adhesion

Answer 5

Attraction of water molecules for solid surfaces is known as adhesion.

Question 6

Surface tension

Answer 6

Surface tension is a property of liquids, and as a result of unbalanced forces near the surface that cause the surface to be stretched.

Question 7

Capillarity

Answer 7

Capillarity, capillary rise, or wicking is the ability of a liquid to flow through the small spaces, known as capillaries, without any external support and against gravity.

Question 8

Potential energy

Answer 8

The potential energy is due to the position and internal condition of a body that allows it to do work. Potential energy (PE) of an object is provided by gravity and is given as follows: P.E= mgh

Question 9

Kinetic energy

Answer 9

The kinetic energy (KE) is due to the motion of a body and is given as: K.E = 1/2m v2

Question 10

Electrical energy

Answer 10

Electrical energy is a product of the electric potential (V) and the unit charge moved (Q).

Question 11

Water potential

Answer 11

The water potential at any given location is the difference in potential energy of water at that location and a reference location containing pure water. Ψw

Question 12

Gradient of flow

Answer 12

The driving force for the flow is known as the gradient of flow or soil water potential gradient and is defined as the change in potential energy with distance.

Question 13

Matric potential

Answer 13

The water potential resulting due to capillary and adsorptive forces of soil matrix is known as matric potential.
Ψm = the force with which water is held in soil solids.

Question 14

Gravitational potential

Answer 14

Gravitational potential is the force of gravity that is acting on soil water exactly as it does on any other body. Or
Ψg/z = vertical distance from an arbitrary reference elevation to the point in question.

Question 15

Osmotic potential

Answer 15

It is also known as solute potential and is a measure of the attraction of water to salts in the soil water film.
Ψo/s = the water potential caused by solutes in the soil or plant water system where there is a semipermeable membrane present.

Question 16

Pressure potential

Answer 16

Pressure potential is the height of water above a specific point in the soil or at the soil surface. Ψp

Question 17

Overburden potential

Answer 17

The potential due to the overlaying weight of the soil is known as the overburden potential. Ψb

Question 18

Total soil water potential

Answer 18

The amount of work per unit quantity of pure water that must be done by external forces to transfer reversibly and isothermally an infinitesimal amount of water from a pool of pure water at a specified elevation at atmospheric pressure to the soil water at the point of interest. Ψt