3_Water_and_Life_Lecture_Slides

Polar covalent bond

A type of bond where electrons are shared unequally between atoms, resulting in partial charges.

What kind of molecule is water (H2O)?

polar molecule; the electrons spend more time near the oxygen than the hydrogen.

Hydrogen bond

A weak attraction between a hydrogen atom in one molecule and an electronegative atom in another molecule.

What are four of water’s properties that facilitate an environment for life?

cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent.

Cohesion

The tendency of water molecules to stick together due to hydrogen bonding; results in high surface tension.

Surface Tension

The property of water that allows it to resist external force, due to cohesive forces between water molecules at the surface.

Adhesion

the ability to work itself up something, like plant cell walls; helps to counter the downward pull of gravity.

Kinetic Energy

the energy in motion, affects the movement of water molecules and influences temperature.

Potential energy

stored energy, based on position or structure.

Thermal Energy

the total energy of all the particles in a substance, related to temperature and heat transfer. ATOMS THAT ARE MOVING.

Heat

thermal energy in transfer from one body of matter to another.

calorie (cal)

the amount of heat required to raise or lower the temperature of water by 1degreeC.

Specific heat

The amount of heat (energy) required to increase or decrease a temperature

Heat is absorbed when hydrogen bonds…

break

Heat is released when hydrogen bonds…

form

Heat of vaporization

The amount of heat a liquid must absorb for 1 g of it to be converted to gas.

Heat of vaporization

the heat a liquid must absorb for 1g to be converted to gas.

Evaporative cooling

A process which liquid evaporates, its remaining surface cools.

Water is __ dense as a solid than as a liquid

less

At what degree does water reach its greatest density?

4 degrees celsius.

Solution

a liquid that is a completely homogeneous mixture of substances.

Solvent

dissolving agent of a solution (what does the dissolving)

Solute

the substance that is dissolved (what is being dissolved)

Aqueous solution

water is the solvent.

Hydration shell

the layer of water molecules that surrounds and interacts with a solute particle in a solution.

Hydrophilic substance

a substance that has an affinity for water and can interact favorably with it.

Hydrophobic substance

a substance that repels water and does not interact favorably with it.

What do you use to calculate the number of solute molecules in an aqueous solution?

mass

Molecular mass

the sum of all masses of all atoms in a molecule

Avogadro’s number

the number of particles in one mole of a substance, approximately 6.022 x 10²³ daltons= 1g

Molarity (M)

the number of moles of solute per liter of solution

A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other:

-the molecule that lost the proton is now a hydroxide ion (OH-)

-the molecule with the extra proton is now a hydronium ion (H3O+), though it is often represented as H+.

dynamic equilibrium

water molecules dissociate at the same rate which they are being reformed.

dissociation of water

2 H2O ⇌ H3O+ + OH-

Concentrations of H+ and OH- are ___ in pure water

equal

acid

substance that increases the H+ concentration of a solution

base

a substance that reduces the H+ concentration of a solution.

equation of pH of a solution

pH = -log[H+]

example: [H+]= 10 ^-7, so

pH= - (-7) = 7

acidic solution pH values

less than 7

basic solutions pH values

greater than 7.

What is the internal pH of most living cells?

close to 7.

Buffers

are substances that help maintain a stable pH in biological systems by neutralizing acids and bases.

What is the main product of fossil fuel combustion?

CO2

ocean acidification

CO2 dissolved in seawater forms carbonic acid

How does bicarbonate ions form?

H+ ion combine with carbonate ions