Properties of Water

Key Takeaways: 1. List and explain the four properties of water that emerge as a result of its ability to form hydrogen bonds 2. Distinguish between the following sets of terms: hydrophobic and hydrophilic substances; a solute, a solvent, and a solution 3. Define acid, base, and pH

What percent of cells are water?

70-95%

Is a water molecule polar or non-polar?

polar

What kind of bond do water molecules form with each other?

hydrogen bonds

!!! What are four of water’s properties?

1. Cohesive behavior

2. Ability to moderate temperature

3. Expansion upon freezing

4. Versatility as a solvent

What is cohesion?

Hydrogen bonds hold water molecules together

What is an example of cohesion?

Helps the transport of water against gravity in plants

What is adhesion?

an attraction between different substances

What is an example of adhesion?

Water and plant cell walls

What is surface tension?

A measure of how hard it is to break the surface of a liquid

Is surface tension related to cohesion or adhesion?

Cohesion

Water can absorb or release a large amount of heat with a small/big change in its own temperature.

small

What does water’s high heat of vaporization allow for?

It allows for the evaporative cooling of the surrounding environment, which allows living organisms to maintain homeostasis.

What is specific heat?

the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree Celsius.

What is the specific heat of water and what effect does it have?

1 cal/g/degree Celsius. This high specific heat minimizes temperature fluctuations to within limits that permit life.

Why does water have a high specific heat?

Heat is absorbed when hydrogen bonds break, and heat is released when hydrogen bonds form.

Which is more dense—ice or liquid water?

Liquid water

!!! What is a solution?

A liquid that is a homogeneous mixture of substances

!!! What is a solvent?

The dissolving agent of a solution

!!! What is the solute?

The substance that is dissolved

What is an aqueous solution?

One in which water is the solvent

Why is water a versatile solvent?

Due to its polarity, which allows it to form hydrogen bonds easily

What is a hydration shell?

After an ionic compounds is dissolved in water, the hydration shell is the sphere of water molecules that surround each ion

True or false: a hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other.

True

The hydrogen atom leaves its electron behind and is transferred as a proton, or hydrogen ion (__)

H⁺

The molecule with the extra proton is now a hydronium ion (__), though it is often represented as __.

H₃0⁺, H⁺

The molecule that lost the proton is now a _________ ion (__).

hydroxide, OH^-

What does water being in a state of dynamic equilibrium mean?

Water molecules dissociate at the same rate at which they are being reformed

Are concentrations of H⁺ and OH^- equal in pure water?

Yes.

Acids and bases modify the ________ of H⁺ and OH^-.

concentrations

What is an acid?

Any substance that increases the H⁺ concentration of a solution

What is a base?

Any substance that reduces the H⁺ concentration of a solution

Most biological fluids have a pH range of __ to __.

6 to 8

____ are substances that minimize changes in concentrations of H⁺ and OH^- in a solution.

Buffers