The properties of water make it essential to life. Cohesion refers to its ability to form hydrogen bonds, attracting the molecules together and contributing to its high surface tension. Adhesion refers to water's attractive properties to other substances, and helps processes like absorption through the xylem. Solid ice is less dense than liquid water, allowing life to exist below the frozen surfaces of lakes and ponds. The polarity of water is essential for numerous biological processes and makes it a good solvent for most biological molecules. Finally, the high specific heat of water makes it resistant to temperature change, allowing life forms to maintain relatively constant internal temperatures.

The high specific heat and surface tension of water contribute to its high boiling point, helping to keep it in liquid form for most biological processes.

Adhesion refers to the attraction between water molecules and foreign particles or surfaces. Cohesion refers to the attraction between one water molecule and another.

Adhesion of water to the cell walls of the xylem vessels and cohesion of water molecules to one another allow for water transport in plants. This is also known as capillary action.

The high heat capacity, low solid density, and polarity of water, as well as its use as a solvent, are all essential to the role of water in supporting life in other ways.

The high specific heat of water means that it requires a large amount of heat to raise the temperature of water. This helps the temperature of the environment from becoming too hot or too cold. Also, humans are about 66% water, thus this property of water helps us regulate our body temperature too. Evaporative cooling helps prevent bodies from overheating. We have evolved to take advantage of this property of water, perspiring through our skin to cool it down during exercise. The fact that ice floats protects lakes from further cooling by cold wind. The fact that water is such a good solvent for polar molecules allows the chemistry of life to occur. Recall that life uses four main biomolecules, and dehydration synthesis and hydrolysis reactions occur constantly.

In osmosis, water diffuses through selectively permeable membranes to regions where the concentration of solute is higher (hypertonic).  Osmosis is not the movement of the solute particles.

A hypertonic solution has a higher concentration of solute than the solute in the cell.  Water diffuses to the higher concentration of solute, so water diffuses out of the cell, and the cell shrivels up. One way to think of this is that water follows "salt," as salt is the most common biological solute.

When the solution is hypotonic to the cell, the concentration of solute outside the cell is less.  The water diffuses to the higher concentration inside the cell and causes the cell to swell with water, at it may burst. 

The bond between oxygen and hydrogen in water molecules involves the sharing of electrons in which the oxygen atom pulls the electrons towards it more than the hydrogen pulls the electron.  This results in a slight negative charge on the oxygen and a slight positive charge on the hydrogen.  The bond is not ionic because electrons are not totally transferred, rather they are shared.

The correct answer is covalent bonds because they are the strongest of all bonds present in a water sample. Although hydrogen bonding is present in water it is not the strongest bond in a sample of water. The bonds that make up the water molecule themselves are strongest. Ionic bonds do not exist in water.

Hydrogen bonds are the intermolecular forces that allow it to engage in cohesion.  Ionic bonds are strong bonds within a molecule between a cation and anion.  Polar covalent bonds are bonds within a molecule in which there is a slight charge on the elements.  Nonpolar covalent bonds are bonds within a molecule in which there is no charge on the elements.

Acidic compounds and solutions release hydrogen () ions.  Basic compounds and solutions release  ions and take up hydrogen ions.  Because of their charge acidic compounds and solutions do not mix well with oil, which is nonpolar.