1. Journal Question If you have ever seen a photograph of Earth from space, you know that much of the planet is covered by water. Water makes life on Earth possible. If life as we know it exists on some other planet, water must be present to support that life. a.) Try to make a list of 10 things that have water in them b.) Compare your list to another student and add to your list c.) Did either list contain any living things?

2. Properties of Water Biology - Irwin

3. Why is Water So Important??

4. The Water Molecule – H2O  In your journal, draw the hydrogen and oxygen atom like we have done earlier in the unit (Bohr Model)  How many protons (+) are in the nucleus of an oxygen atom?  How many protons (+) are in the nucleus of a hydrogen atom?  Does the nucleus of the oxygen atom or the hydrogen atom attract electrons more strongly?

5. Water molecules are polar  Polar because of an uneven distribution of electrons between the oxygen and hydrogen atoms  A water molecule has both partial negative charges and partial positive charges. O HH (-) (+)

6. Journal Question  Think of the interaction of two magnets and how they either are attracted to each other or repel. Then draw a picture of how you think the water molecules will interact with each other.

7. Hydrogen Bonding  Polar water molecules can attract each other.  Hydrogen atom with partial positive charge (+) is attracted to the partial negative charge (-) of another atom (oxygen)  This is known as a hydrogen bond  Not as strong as covalent or ionic bonds  Bonding between molecules

8. Activity #1 – Penny Wars  For this mini lab you will need:  Penny  Paper towel  Small beaker (cup) of water  Dropper  Each student will write down their prediction for how many drops of water that can be held on the penny (heads or tails) until the water spills over onto the paper towel.

9. Properties of Water  Cohesion

10. Cohesion  Attraction between molecules of the same substance (water)  Water molecules can form up to four hydrogen bonds at the same time so it is very cohesive.  Examples:  Beads of water on leaves  Raft spider  Surface tension – glass of milk that is poured to very top and somehow doesn’t spill.

11. Activity #2  Part 1: For this mini lab, you will add water to the Petri dish from a small beaker. Use your fingers to “float” the small paper clip on the surface of the water.  Record your observations  Part 2: Add two drops of soapy water with a dropper to your Petri dish  Record your observations

12. Follow-Up Lab Questions  Penny Wars: How many drops of water could your penny hold before it spilled over onto the paper towel?  Penny Wars: What property of water made it possible for so many drops of water to stay on the penny? Explain!  Soap and Paper Clips: How did the paper clip “float” on top of the water?  Soap and Paper Clips: Why did the paper clip sink once the soap was added to the Petri dish?

13. Properties of Water  Adhesion

14. Activity #3 – Water in Graduated Cylinders  In your group, add water into your glass graduated cylinder until it is about half full. Remember how we discussed earlier in the year that the meniscus is the curvature you see at the the water level line.  Draw a sketch of your water in the graduated cylinder and label the meniscus

15. Adhesion  Attraction between molecules of different substances  Ex.) Water forms “meniscus” in graduated cylinder  Adhesion between water molecules and glass molecules is stronger than cohesion between water molecules

16. Activty #4 – Capillary Action in Flowers  We know that plants are mainly made up of water, but how does it get from the soil up to the leaves of the plant?  Capillary Action!

17. Question:  Think about an extremely hot day in the summer that is followed by a very cold rainy day. Are the fish and other aquatic organisms in Lake Michigan in danger due to very high or low water temperatures?  NO. Water absorbs large amounts of heat with only very small changes in temperature, so aquatic organisms are protected by drastic temperature changes.

18. High Heat Capacity  Heat Capacity: Amount of heat energy needed to increase waters temperature  Water had a high heat capacity due to the hydrogen bonds between molecules  A large amount of heat energy is needed to cause the molecules to move faster and raise the temperature of water.

19. Ice  Why does ice float in water?

20. Why does ice float in water?  Water is less dense as a solid than a liquid  Solid water (ice) = less dense  Liquid water = more dense  Example: Rocks and water  Solid water floats

21. Mixture  Mixture: Material composed of two or more elements or compounds that are physically mixed together but not chemically combined.  Examples:  Salt and pepper mixed together  Sugar and sand mixed together  Two types of mixtures:  Solutions  Suspensions

22. Solutions  Solution: all components are evenly distributed throughout the solution  Solute: substance that is dissolved  Solvent: substance in which the solute dissolves  Aqueous solutions: Solutions where the solvent is water

23. Mini Lab  At your table, fill your test tube up about half way with water.  Add a small pinch of salt and gently mix together until dissolved.  Identify the solvent, solute and solution.  Is this an aqueous solution? Why?

24. How does water dissolve table salt?  Table salt (NaCl)  Remember that NaCl is bonded together by an ionic bond. Write out the two ions with their charges for table salt.  Draw a solid piece of salt at the molecular level.  Draw a water molecule, and add its partial charges.  Remember water is POLAR!  How do you think water dissolves table salt?

26.  http://www.4shared.com/video/I9Huy_EY/Dissociation_of_sa lt.html?cau2=403tNull

27. Water is the Best Solvent on Earth!  Since water is polar, it can dissolve ionic compounds and other polar molecules  Can dissolve salts, sugars, minerals, and some gases

28. Mini Lab Part 2  Dump out the water and salt solution and add about 15 mL of water and a large spoon full of salt.  Gently shake the solution until the salt is dissolved  What did you notice?  Saturated solutions: when solvent has dissolved all of the solute possible  Unsaturated: not all of the solute have been dissolved by the solvent

29. Suspensions  Suspensions: when some materials do not dissolve when placed in water  Materials separate into very small pieces so they do not settle out right away.  Water molecules are always moving so they keep small particles suspended for a period of time  Examples:  Blood is a suspension  Flour in water is a suspension

30. Acids and Bases  Water molecules sometimes split apart to form ions. H 2 O  H + + OH - Water  hydrogen ion + hydroxide ion  Pure water is neutral  # H + = # OH -

31. pH Scale  Indicates concentration of H + ions in a solution

32. pH Scale  Neutral: pH of 7  Concentration of OH - and H + are equal  Acids:  Compounds that form H + ions in a solution  More H + than OH -  Bases:  Compound that produces hydroxide (OH-) ions in solution  Alkaline  More OH - than H +

33. Buffers  Buffers prevent drastic changes in pH  Buffers: weak acids or bases that can react with strong acids or bases to prevent sudden changes in pH