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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