Transcript Chapter 4 Section 4 Unique Properties of Water
Chapter 4 Section 4 Unique Properties of Water
Mrs. Kerstetter Biology
Structure of Water
All living things are dependent on water Cells are surrounded by fluid that is mostly water Cells are 70-95% water Formula for water?
H 2 O H atoms are joined to O atoms by a
Key to water’s unusual properties:
Electrons of each covalent bond are not shared equally between the H & O atoms Oxygen has a stronger attraction The unequal sharing causes the Oxygen to have a slightly negative (-) charge, while the hydrogen ends have a slightly positive (+) charge
A molecule in which opposite ends have opposite electrical charges is called a POLAR molecule Water is a polar molecule
How are water molecules attracted to each other?
Slightly negative O attracts the slightly positive hydrogen of adjacent molecules, causing molecules to become arranged using hydrogen
Water’s Unique Properties
Cohesion and Adhesion Temperature Moderation Low Density of Ice Ability to Dissolve Other Substances
Cohesion and Adhesion
Cohesion tendancy of molecules of the same kind to stick to one another Much stronger for water than other liquids Adhesion Attraction between unlike molecules Important to keep large groups of molecules organized in living world
Thermal energy Total amt of E associated with the random movement of atoms and molecules in a sample of matter Temperature Measure of the average E of random motion of particles in a substance Is temperature transferred from warmer to cooler or cooler to warmer?
Warmer to cooler
Temperature rises bc the molecules move faster In water, some of the E goes to break bonds, so doesn’t heat as fast When you cool a substance the molecules slow and temp drops BUT In water, it forms H bonds, so doesn’t cool as much as a metal
Examples of Temp Moderation of Water
Oceans and lakes moderate the temperature of nearby land masses El Nino Evaporation and sweat
Low Density of Ice
Formula for ice?
Water is more dense than ice Why?
Hydrogen bonds Longer lived bc slower moving than liquid form Why is this important to living things?
Ability to Dissolve Other Substances
Solution Uniform mixture of 2 or more substances Salt water Solute Substance that is dissolved and present in a lesser amount salt Solvent Substance that dissolves the other substance and is present in a greater amount water Aqueous solution When chemical dissolved in water
Water is the main solvent in all cells and in plant sap Polar molecules are easily broken down by water