[BIO 111] Ch 3 - Water and Life

Emergent properties of H2O

• Cohesion

• Adhesion

• Moderates temperatures

• Universal solvent

Cohesion

H2O ability to hold other H2O molecules

Adhesion

attraction between different substances

Surface tension

how much force must be used to break the surface of a liquid

Why does H2O have a high surface tension?

Due to arrangement of H2O molecules and their hydrogen bonds

Thermal energy

kinetic energy associated with random motions of atoms or molecules

Temperature

average kinetic energy of molecules

Heat

transfer of thermal energy

Calorie (cal)

amount of energy required to change the temperature of 1g of H2O by 1C

Joules

unit of energy

1 cal is equal to how many joules?

4.184 J

Specific heat

amount of energy needed to change to temperature of 1g of a substance by 1C

What special ability does H2O have because of it’s high specific heat?

It can absorb large amounts of heat without drastic temperature changes

What does heat do when hydrogen bonds are broken? — evaporization

It’s absorbed

What does heat do when hydrogen bonds are made? — condensation or solidification

It’s released

Heat of vaporization

energy needed for 1g to convert to gas

Evaporative cooling

process where surface of an object becomes cooler during vaporization

Why is evaporative cooling important for organisms? What’s an example?

It helps them regulate their internal temp, sweating

Why does ice float in liquid water?

Movement of molecules slows and makes hydrogen bonds more order and spaced out

Solution

homogenous mixture of substances

Solvent

substance doing the dissolving

Solute

substance being dissolved

Aqueous solution

anything dissolved in H2O

What kind of molecules can water dissolve?

nonionic polar molecules

Hydrophilic

affinity for water, usually polar

Hydrophobic

no affinity for water, usually nonpolar

Molecular mass

sum of all atoms masses in a molecule

1 mole

6.022×10²³ molecules

Hydrogen ion

H+, also known as a proton

Hydroxide ion

OH-

Acid

solution with a high concentration of H+ ions, pH between 0-6.99

Base

solution with high concentration of OH- ions, ph between 7.1-14

Most biological fluids have a pH of…

6 to 8

Buffers

substances that maintain a specific pH level

When an acid is added to a buffer solution, the buffer…

Accepts H+ ions

When a base is added to a buffer solution, the buffer…

Donates H+ ions

Ocean acidification

dissolved CO2 in water increases decreases its pH

Why is ocean acidification bad for oceanic organisms?

it decreases the amount of carbonate in the ocean which is needed for calcification

How much human-made CO2 is absorbed by the ocean?

25%