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Water and Life

Water and Life. The Molecule That Supports Life. Item 1. Water is the biological medium. ¾ of the Earth is covered by water. Living cells require water and are made up of 70-95% water. Exists in all 3 phases naturally on Earth. Life began in water over 3 billion years ago. Item 2.

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Water and Life

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  1. Water and Life

  2. The Molecule That Supports Life Item 1 Water is the biological medium ¾ of the Earth is covered by water Living cells require water and are made up of 70-95% water Exists in all 3 phases naturally on Earth Life began in water over 3 billion years ago Item 2 Item 3 Item 4

  3. Water is Made of Polar Covalent Bonds Intramolecular force: polar covalent bond – unequal electron sharing The overall molecule is also polar – overall distribution of electrons is unequal. Intermolecular force: Hydrogen bonds  the slightly negative O of one water molecule attract the slightly positive H ends of neighboring water molecules. 4 H bonds per molecule! Last for trillionths of a second Sheer quantity implies many bonds at a given time.

  4. Cohesion of Water Molecules A second line of text here • H bonds keep water molecules linked creating a more structured liquid than most. • This phenomenon is know as cohesion • Cohesion helps drive water transport in plants • Adhesion – the attraction between 2 different substances also helps (water to cells) • Water also has a high surface tension!

  5. Water Moderates Temperature • Water can absorbs and store heat from the air • Water has a very high Specific Heat relative to other substances. 1cal/g×°C • Means it takes a great deal of energy to change the temperature of water! • What are some of the impacts on life of this specific heat?

  6. Evaporative Cooling • Water also has a high heat of vaporization (energy needed to convert 1g of liquid to gas). • Regulates temperature stability of bodies of water. • “hottest” molecules vaporize first – leaving the remaining surface slightly cooler.

  7. Density of Water vs. Ice Liquid water is more dense than solid water This is directly caused by the hydrogen bonding of water. Above 4°C water behaves like most liquids. From 4-0°C water starts to freeze due to lack of movement. 0°C locked in crystalline lattice.

  8. Water: The Solvent of Life Water can dissolve Ionic bonds due to the positive and negative regions of the molecule. As long as a molecule has a polar region the water can generate H bonds with it. Hydrophobic: Water-fearing. Non-ionic and Non-polar. Do not mix with water! Hydrophilic: Water-loving. Does not need to dissolve, but will generate bonds with the water.

  9. Solubility: Dissolving and Solutions

  10. Water is a Polar Covalent Solvent • Add a subtitle here An accent, click to edit the text inside. • This text is a placeholder. • Here is the second level. • You may change this text • Here is the third level • Formatting is controlled by the slide masterand the layout pages. • There is a third level • And even a fourth level An accent, click to edit the text inside.

  11. Water as an Acid or Base Water is amphoteric Acid Base • Acids increase H ions in a solution. • Acids increase the pH • Bases reduce H ions concentrations. • Bases decrease the pH pH measures the negative log of the hydrogen ion concentration.

  12. Water is a Buffer • Most living things require an optimal pH of 7 (neutral). • A buffer is a substance that minimizes changes in H and OH concentrations.

  13. Smart Art Page Layout PowerPoint 2007 Enhanced Version This chart utilizes Smart Art which is feature in PowerPoint 2007. If you wish to make charts like this and don’t have PPT 2007, we have provided the graphical elements to help you build this yourself. Here is the description of the chart. You may change or delete this text as you wish. Here is a placeholder for more text and description of the chart. Changing this text will not interfere with the formatting of this template.

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