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

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++

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