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Properties of Water

Properties of Water. Water. The universal solvent in living things which makes up over 90% of cells and the majority of Earth. Why water works well in living things. Water is Polar and is really good at dissolving substances Water is needed for all cellular chemistry

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Properties of Water

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  1. Properties of Water

  2. Water The universal solvent in living things which makes up over 90% of cells and the majority of Earth

  3. Why water works well in living things • Water is Polar and is really good at dissolving substances • Water is needed for all cellular chemistry • Water molecules adhere to some things • Water molecules stick together • Water molecules form surface tension • Ice floats • Water has a high specific heat

  4. Some substances adhere to water, others are repelled • Hydrophilicmeans watermolecules are attracted to this substance • “Water Loving” • Hydrophobic means water molecules are repelled from this substance • “Water Fearing”

  5. Universal solvent • Water is a solvent (it dissolves stuff for living things) • Water can dissociate (break apart) most ionic compounds such as salts. • Solutes + Solvent = Solutions

  6. Reflection Writing • Why do we look for water on other planets like Mars?

  7. Water molecules are Polar • 2 hydrogen + 1 oxygen (H2O) •  = delta = slightly - O H H + +

  8. Polarity • Water molecules are polar. • Polarity: one end of molecule positively (+) charged and other end negatively (-) charged • Polarity causes hydrogen bonding between water molecules

  9. Hydrogen Bonding • Weak bonds between a hydrogen of one molecule to an adjacent negative molecule • Ex: attraction between water molecules.

  10. Drawing of a water molecule indicating the charges.

  11. Cohesion • Water molecules are attracted to each other. • Water molecules “stick” together. Hydrogen Bonds

  12. Cohesion causes Surface Tension • Surface Tension • Water molecules tend to stick together, forming a sort of “skin” • Some animals can use this “skin” as surface on which it can walk. Water strider spider

  13. Surface Tension • What properties of water makes a belly flop hurt so bad? • http://www.youtube.com/watch?v=N8gavevFX-0&feature=fvsr

  14. Adhesion • Water molecules stick to other molecules (not water) • Water molecules are attracted to surfaces that have charges (hydrophilic). • Water molecules are repelled from surfaces that have no charge (hydrophobic).

  15. Capillary action in Plants

  16. Density • Water becomes less dense (more space between molecules) when it freezes.

  17. Density How does DENSITYaffect ecosystems? • Ice floats, creating buffer from cold air, enabling organisms to still survive underneath the frozen surface.

  18. Properties of Water Lab • What are the properties of water that make it important for life? • Why do all living cells require water? • Why is water called the universal solvent?

  19. Surfactants • Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid. • Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. • Why are surfactants used in an automatic dishwasher?

  20. Properties of Water Lab • Use your Notes & Discussion from powerpoint • After notes and discussion on the properties of water, write a hypothesis about how many drops of water you should be able to fit onto a penny • Each groups does 5 trials • Average the results and put them on the class data table • Copy data from class data table • Calculate the % error • Create a bar graph of the data. • Answer the conclusion questions on your lab sheet

  21. Water Lab

  22. Acids, Bases & pH scale

  23. Acids • Compounds that forms H+ ions in solution. • pH values below 7. • Acids taste sour • The lower the pH number the stronger the acid. • Ex. Stomach acid, Vinegar, Lemon juice.

  24. Bases • Compounds that produces hydroxide ions (OH-) in solution. • Also known as alkaline solutions • pH values above 7. • Bases taste bitter • The higher the pH the stronger the base. • Ex. Ammonia, soap, bile.

  25. pH scale • Used to indicate the concentration of H+ ions in a solution. • Ranges from 0 to 14. • At a pH of 7, the concentration of H+ ions and OH- ions are equal. • Pure water has a pH of 7. • Each step on the pH scale represents a factor of 10.

  26. The following slides have MANY different looking pH scales • They all say the same thing, just be used to seeing a variety for the class assessments

  27. pH Scale

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