2.2 Properties of Water KEY CONCEPT Water’s unique properties allow life to exist on Earth.

2.2 Properties of Water

KEY CONCEPTWater’s unique properties allow life to exist on Earth.

2.2 Properties of Water

OHH

_

++

Life depends on hydrogen bonds in water.• Water is a polar molecule.

– Polar molecules have slightly charged regions.– Nonpolar molecules do not have charged regions

Atom: Oxygen

Charge: negative (-)

Atom: Hydrogen

Charge: positive (+)

1. Weak Hydrogen bond2. Explain: form between slightly positive and slightly negative atoms---break easily

O HH

_

++ OHH

_

++

2.2 Properties of Water

• Properties of water related to hydrogen bonds:

1. Capillary action in plants….water moves up roots

2. Cohesion-water likes to bond with other water molecules (are cohesive or tight)

3. Adhesion-water will stick to or adhere to the sides of things

2.2 Properties of Water

Many compounds dissolve in water.

• A solution is formed when one substance dissolves in another.– Solvents dissolve other substances-usually water– Solutes dissolve in a solvent.

solution

2.2 Properties of Water

Some compounds form acids or bases.

• An acid releases a hydrogen ion when it dissolves in water.– high H+ concentration, taste sour…– pH = 1-6.9 (1 is strongest acid, 6.9 is weakest)

more acidic

stomach acid pH between 1 and 3

2.2 Properties of Water

• A neutral solution has a pH of 7.

pure water pH 7

2.2 Properties of Water

• A base removes hydrogen ions from a solution.

– low H+ concentration, taste bitter….are slippery– Called basic or alkaline– pH = 7.1-14 (7.1 is weakest base, 14 is strongest)

bile pH between 8 and 9

more basic