+ Basic Chemistry Honors Bio Ms. Napolitano. + Water is everywhere! The Earth is ~71% water The human body is made up of about 55- 78% water Water is.

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Basic Chemistry

Honors BioMs. Napolitano

+Water is everywhere!

The Earth is ~71% water

The human body is made up of about 55-78% water

Water is a polar molecule

Molecules of water are held together by hydrogen bonds

+Properties of Water

1. Cohesion –the attraction of H2O molecules to other H2O molecules due to hydrogen bonding

Adhesion – attraction of H2O to other substances

Capillary Action - ability of H2O to move within narrow spaces against gravity

Surface Tension – cohesive forces at the surface of H2O

+Properties of Water

2. Expansion upon freezing

Solid state is less dense than liquid state

Begins to expand at 4°C Floating ice creates

insulation for underneath, allows for life in aquatic ecosystems

+Properties of Water

3. Universal solvent Solute – substance being dissolved Solvent – dissolving agent Solution – homogenous mixture of 2 or more

substances Aqueous solution – water is the solvent

Water forms a hydration shell around ionic compounds

Water dissolves polar compounds Hydrophilic – “water loving”, affinity for

H2O Hydrophobic – “water fearing”, repels H2O

+Properties of Water

4. Moderate Temperature Specific Heat – amount of heat that must be

absorbed or lost for 1g of substance to change 1°C

Calorie – amount of heat to raise 1g of water by 1°C

Water has high specific heat: 1 cal/g/°C Due to hydrogen bonding

Water has high heat of vaporization Moderates climate

Evaporative cooling prevents organisms from overheating

+10/21 - Do Now

Please take out your homework and a piece of notebook paper.

Grab your clickers!

+Properties of Water

4. Moderate Temperature Specific Heat – amount of heat that must be

absorbed or lost for 1g of substance to change 1°C

Calorie – amount of heat to raise 1g of water by 1°C

Water has high specific heat: 1 cal/g/°C Due to hydrogen bonding

Water has high heat of vaporization Moderates climate

Evaporative cooling prevents organisms from overheating

+Hydration Sphere

+Hydration Sphere

+pH

Dissociation: the breaking apart of 2+ molecules

Usually capable of recombining

In water, one H+ ion shifts from one molecule to the other

+pH Acid – increases H+ concentration of a solution

HCl H+ + Cl-

H2CO3 HCO3- + H+

Base – reduces H+ concentration of a solution

NH3 + H+ NH4+

NaOH Na+ + OH-

Acids and bases that dissociate completely in water are called strong acids and strong bases, respectively.

+

Measure of H+

concentration

pH is lower as H+ concentration increases

pH is higher as H+ concentration decreases

pH 7 = neutral

The pH Scale

+Buffers Many bodily processes are pH specific

Most living cells have pH of ~7

Buffers – substances that minimize change in H+ and OH- concentrations in a solution

Accept or donate H+ ions

Usually contain a weak acid and corresponding base