Water

Chapter 6:2

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Water

• Life is inextricably tied to water

• Covers almost ¾ of Earth’s surface

• Your body is made up of approximately 60% water

Polarity of Water

• water polarity animation

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Water is polar (has charges).

***Remember- Electrons have a (-) charge, if Oxygen keeps electron longer than Hydrogen then Oxygen’s charge will be slightly (-).

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Polarity

• What does polarity mean?

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Polarity of water

• Within a water molecule, the bonds between oxygen and hydrogen are highly polar (charges unevenly distributed)

• Partial electrical charges develop– Oxygen keeps shared electrons longer so it is

partially negative δ–

– Hydrogen has shared electrons for less time so it is partially positive δ+

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Hydrogen bonds• Cohesion –attraction between molecules

of the same substance

• Attraction produces hydrogen bonds• Each individual bond is weak• Cumulative effects are enormous

Cohesion

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Cohesion

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Hydrogen bonds• Adhesion –attraction between molecules

of different substances• Attraction allows water to bind to other

substances

Hydrogen Bonds

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• Cohesion – water molecules stick to other water molecules by hydrogen bonding

• Adhesion – water molecules stick to other polar molecules by hydrogen bonding

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Properties of water1. Water has a high specific heat

specific heat : The amount of energy required to raise the temperature of 1 gram of a substance by 1 C.

– A large amount of energy is required to change the temperature of water

2. Water has a high heat of vaporization– The evaporation of water from a surface causes cooling of that

surface

3. Ice is less dense than liquid water– Bodies of water freeze from the top down

4. Water is a good solvent– Water dissolves polar molecules and ions

5. Water can form ions

H2O OH– + H+

hydroxide ion hydrogen ion

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Properties of water3. Ice is less dense than liquid water

– Bodies of water freeze from the top down

hydrogen ion

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Properties of water4. Water is a good solvent

– Water dissolves polar molecules and ions

5. Water can form ions

H2O OH– + H+

hydroxide ion hydrogen ion