Water and Life

Solute

The substance that is dissolved in a solution (ex: salt in saltwater)

Solvent

the substance that does the dissolving; usually present in the greatest amount (ex: water in saltwater)

Solution

a homogeneous mixture of solute(s) dissolved in solvent (ex, saltwater)

Hydrophilic

“water-loving”; molecules that are polar and dissolve easily in water

Hydrophobic

“water-fearing”; molecules that are non-polar and do not dissolve in water (ex, fats, oils).

Acid

A substance that increases the concentration of H+ (protons) in a solution; pH less than 7

Base

A substance that decreases the concentration of H+ (often increases OH-); pH greater than 7

Buffer

A substance that resists changes in pH by accepting or donating H+ ions

Density of ice

Ice is less dense than liquid water, which is why it floats. The hydrogen bonds hold water molecules farther apart in solid form

high specific heat

Water can absorb or release a lot of heat without a significant change in temperature, which helps regulate temperature in environments and cells

high heat of vaporization 

Water requires a large amount of energy to change from liquid to gas, which helps cool surfaces (like when we sweat). 

Adhesion

The attraction between water molecules and other substances (ex: water sticking to plant walls).

Capillary action

The ability of water to move up narrow tubes against gravity due to cohesion and adhesion (ex, water traveling up plant roots and stems).

Cohesion 

The attraction between water molecules, which helps form droplets and allows surface tension

Surface tension

a “skin” on the surface of water caused by cohesive forces, making it resistant to external force

Oxygen is more electronegative than hydrogen.

true

Oil doesn't dissolve in water because

it is nonpolar

In one water molecule, what type of bond forms between the O and H atoms?

polar covalent bond

Buffers are substances that help resist shifts in pH by

both donating H⁺ to a solution when bases are added, and accepting H⁺ when acids are added.