Water Objectives: Describe the structure of a water molecule List and describe water’s unique properties

Think, Pair, Share Why is water so important to life? What makes water so special?

Water and Living Things Water is the most abundant molecule in living things. Water has special traits that make it important to life.

Polarity Water is a compound made up of polar molecules. A polar molecule is a molecule in which opposite ends have opposite electric charges. Negative charge Positive charge Electrons spend more time near the oxygen atom since its greater number of protons exerts a greater pull on the electrons. This imparts a slight negative charge to the oxygen portion of the water molecule. By default, the hydrogen atoms are left with a slight positive charge.

Hydrogen bonding Hydrogen bonds form when a covalently-bonded H+ is attracted to a negatively-charged atom in a neighboring molecule. Because of its polarity and hydrogen bonding, water has unique characteristics that benefit living things.

Online Activity 4.4 How are 2 water molecules like 2 magnets?

Characteristics of water: Water’s Life-Supporting Properties Cohesion Adhesion High Specific Heat Capacity Low Density of Ice Ability to Dissolve Other Substances

Characteristics of water: Cohesion Refers to the tendency of molecules of the same kind to stick together. This is stronger for water than other liquids. Example:

Characteristics of water: Adhesion Refers to the attraction that occurs between unlike molecules. Example: Water is able to travel against gravity up a tree trunk.

High Specific Heat Capacity Refers to the quantity of heat required to raise the temperature of a unit mass of the substance by one degree C. Water requires a lot of heat to change its temperature. Example:

Characteristics of water: Low Density of Ice Density refers to the amount of matter in a given amount of space. Ice (solid form of water) is less dense than water (liquid form). As a result, when a pond or lake freezes, the top ice layer floats on top of the liquid layer. Organisms can live in the liquid layer. Example:

Characteristics of water: Ability to Dissolve Other Substances Solution: a uniform mixture of two or more substances. Solvent: the substance that dissolves the other substance and is present in greater amounts. Solute: the substance that is dissolved by the solvent. Water is the main solvent inside all cells, in blood, and in plants.

Conclusion: Based on the notes, answer these two questions again. Why is water so important to life? What makes water so special?