2.3 Chemistry of Water

Properties of Water

Water has a high heat capacity.

Properties of Water Water has a high heat capacity. –A calorie is the amount of heat energy needed to raise the temperature of 1g of water 1 ° C.

Properties of Water Water has a high heat capacity. –A calorie is the amount of heat energy needed to raise the temperature of 1g of water 1 ° C. –It only takes about 0.5 calories to raise the temperature of most other covalently bonded liquids 1 0 C.

Properties of Water

Water has a high heat of vaporization.

Properties of Water Water is a solvent.

Properties of Water Water molecules are cohesive and adhesive.

Properties of Water Water molecules are cohesive and adhesive. –Water molecules cling together because of hydrogen bonding (cohesion).

Properties of Water Water molecules are cohesive and adhesive. –Water molecules cling together because of hydrogen bonding (cohesion). –Water’s positive and negative poles allow it to adhere to polar surfaces (adhesion).

Properties of Water Water molecules are cohesive and adhesive. –Water molecules cling together because of hydrogen bonding (cohesion). –Water’s positive and negative poles allow it to adhere to polar surfaces (adhesion). –Water is an excellent transport system, both outside and within living organisms.

Properties of Water Water has a high surface tension

Properties of Water Water has a high surface tension –This allows some insects to walk on the surface of a pond or lake.

Properties of Water Frozen water is less dense than liquid water.

Acids and Bases

When water ionizes, it releases an equal number of hydrogen ions (H + ) and hydroxide ions (OH - ).

Acids and Bases

Acidic Solutions (High H + Concentrations)

Acids and Bases Acidic Solutions –Acids are substances that dissociate in water, releasing hydrogen ions (H + ).

Acids and Bases Acidic Solutions –Acids are substances that dissociate in water, releasing hydrogen ions (H + ). –An example: HCl H + + Cl -

Acids and Bases Basic Solutions (Low H + Concentrations)

Acids and Bases Basic Solutions –Bases are substances that dissociate in water, releasing hydroxide ions (OH - ) or take up hydrogen ions (H + ).

Acids and Bases Basic Solutions –Bases are substances that dissociate in water, releasing hydroxide ions (OH - ) or take up hydrogen ions (H + ). –An example: NaOH Na + + OH -

Acids and Bases

The pH Scale

Acids and Bases The pH Scale –Ranges from

Acids and Bases The pH Scale –Ranges from –A pH below 7 is acidic [H + ] > [OH - ]

Acids and Bases The pH Scale –Ranges from –A pH below 7 is acidic [H + ] > [OH - ] –A pH above 7 is alkaline [OH - ] > [H + ]

Acids and Bases The pH Scale –Ranges from –A pH below 7 is acidic [H + ] > [OH - ] –A pH above 7 is alkaline [OH - ] > [H + ] –A pH of 7 is neutral [H + ] = [OH - ]

The pH Scale

Acids and Bases The pH Scale –Each unit change in pH represents a change of 10X

Buffers and pH

A buffer is a chemical(s) that keeps pH within normal limits.

Buffers and pH A buffer is a chemical(s) that keep pH within normal limits. Bicarbonate ions (HCO 3 - ) and carbonic acid (H 2 CO 3 ) found in human blood buffers the pH to 7.4

Buffers and pH If hydrogen ions (H+) are added to the blood, this reaction occurs: H + + HCO 3 - H 2 CO 3 If hydroxide ions (OH-) are added to the blood, this reaction occurs: OH - + H 2 CO 3 HCO H 2 O

2.4 Organic Molecules

Always contain: –Carbon (C) and Hydrogen (H) –A carbon atom may share electrons with another carbon atom

2.4 Organic Molecules Always contain: –Carbon (C) and Hydrogen (H) –A carbon atom may share electrons with another carbon atom

2.4 Organic Molecules Many molecules of life are macromolecules. (macromolecules contain many molecules joined together)

2.4 Organic Molecules Many molecules of life are macromolecules. (macromolecules contain many molecules joined together) –Monomers:Simple organic molecules that exist individually –Polymers:Large organic molecules form by combining monomers

2.4 Organic Molecules

A meal containing carbohydrates, lipids, and proteins.

2.4 Organic Molecules Cells have mechanisms of joining monomers to build polymers

2.4 Organic Molecules Cells have mechanisms of joining monomers to build polymers

2.4 Organic Molecules Cells have mechanisms of joining monomers to build polymers Dehydration Reaction: an -OH and -H are removed Hydrolysis Reaction: the components of water are added

2.4 Organic Molecules