Marvels of Water: Unraveling the Mysteries of a Universal Solvent

1. Objectives • Identify the major properties of water. • Distinguish among the factors that make water a unique substance. • Understand how the presence of substances dissolved in water will affect the properties of water. • pH • Acids & Bases

2. Vocabulary • Cohesion • Adhesion • Solution • Acid • Base • pH • Buffer

3. Employ the Knowledge • Watch the video and write down at least 5 things mentioned about how awesome water is. http://youtu.be/HVT3Y3_gHGg

4. Water • One of the most important substances on Earth. • Without question, one of the biggest reasons life exists as it does. • It looks plain. It’s odorless, tasteless, and everywhere.

5. Water Facts • Biological Facts • We are roughly 75% water!

6. Water Chemistry • Water is constructed from a covalent bond between two hydrogen atoms and an oxygen molecule. • Because of where oxygen’s absent valence electrons are, this bond forms a bent molecule, making it polar. • Being polar is incredibly important to its properties… how it behaves chemically.

7. Water: Not Sharing Electrons Equally Partially - - - - - - - - - - - Partially +

8. Properties of Water • Being polar gives water a partial positive charge on one end and a negative charge on the other. • Specifically; • Oxygen = Negative End • Hydrogen = Positive End • The attraction between the positive (H) of one water molecule and the negative (O) of another causes a bond to form, called a HYDROGEN BOND. • These bonds make most of what water does possible.

9. Water: Polar Molecules The polarity of water makes it able to form polar bonds with other water molecules, called hydrogen bonds, due to the negative oxygen and the positive hydrogen

10. Hydrogen Bonds • All bonds are powerful. • It takes energy to break these bonds. • Some bonds are more powerful than others. • The hierarchy of bonds: • Covalent (strongest) • Ionic • Hydrogen (weakest)

11. Properties • Water’s ability to form hydrogen bonds is responsible for many of its properties. Some of these properties are: • Floats in Solid State • High Heat Capacity/Specific Heat • High Heat of Vaporization • Cohesion: Surface Tension • Adhesion: • Capillary Action • Universal Solvent

12. Property #1: Water Floats when Frozen • When water freezes, the crystal structure formed due to hydrogen bonding makes ice less dense than liquid water. • Because it is less dense than liquid water, when water freezes it floats to the top. • INSULATION: This enables life to survive in warmer temperatures below the ice, insulated from the elements above and prevents most deep bodies of water from freezing solid.

14. Property #2: High Heat Capacity • Water can absorb a large amount of heat without changing temperature. • This property can help organisms maintain a constant internal temperature. • This is mostly due to the hydrogen bonds, again. • When energy in the form of heat enters water it is efficiently distributed the molecules of water by breaking and re-forming new hydrogen bonds • It takes a lot of energy to heat water just 1 degree.

15. Property #3 Heat Capacity & Evaporation • Water is one of the most resistance fluids to boiling and evaporation. • When water is heated, the energy is absorbed in the bonds causing boiling, vaporization, or at least evaporation. • If you add heat to the water then the energy goes into the electrons. • This causes the molecules to become excited and want to break the bonds that holds it with the other molecules. • Heat will break the weakest (hydrogen) bonds first. • This results in evaporation or boiling. Energy

16. Property #4: Cohesion • The attraction of particles of the same substance, such as water, is called cohesion. • Cohesion keeps water from evaporating easily; thus, water is a liquid at ordinary temperatures. • It allows for water to maintain a high surface tension. • What it surface tension? • The resistance water has against something pushing down on it. If the surface tension is greater than the force pushing down, the substance will sit on top of the water… not float, literally sit on top water.

17. Property #5: Adhesion • Water molecules also stick to other polar molecules. This attraction between particles of different substances is called adhesion. • This is important property for plants especially. • This property, along w/ cohesion, allows water to travel upwards through stems and trunk.

18. #6. Capillary Action • Adhesion + Cohesion gives water the property of climbing through tight veins that are made of polar compounds.

19. #7. Universal Solvent • Because of its polarity, water is capable of dissolving many substances with charge (polar stuff and ions) • Therefore, water is an efficient solvent. • This property helps water become a medium for chemical reactions in the body. • What’s dissolved in soda? • Carbon dioxide • HFCS • Salts • Caffeine • Ect.

20. The properties of water revisited • Floats in Solid State • High Heat Capacity/Specific Heat • High Heat of Vaporization • Cohesion: Surface Tension • Adhesion: • Capillary Action • Universal Solvent It is your responsibility to know these properties, be able to define them, and explain why these are biologically relevant.

21. Think-Pair-Share… take a few minutes and read each situation. Decide which property or characteristic is responsible for the process. ANSWER ANSWER ANSWER ANSWER ANSWER ANSWER ANSWER ANSWER ANSWER

22. Water Facts • Water covers 70.9% of the Earth’s surface. • Only 3% of Earth’s water is fresh water. 97% of the water on Earth is salt water... [undrinkable] • 68.7% of the fresh water on Earth is trapped in glaciers, 3% is found in lakes, streams, ponds, and swamps. • 30% of fresh water is in the ground. • Water can dissolve more substances than any other liquid, including sulfuric acid. • A ten meter rise in sea levels due to melting glaciers would flood 25% of the population of the United States. • There is more fresh water in the atmosphere than in all of the rivers on the planet combined. • If all of the water vapor in the Earth’s atmosphere fell at once, distributed evenly, it would only cover the earth with about an inch of water. • Water boils quicker in Denver, Colorado than in New York City. • Approximately 400 billion gallons of water are used in the United States per day. • In one year, the average American residence uses over 100,000 gallons (indoors and outside). • Water is the only substance found on earth naturally in three forms: solid, liquid and gas. • Water makes up between 55-78% of a human’s body weight. • Taking a bath requires up to 70 gallons of water. A five-minute shower uses only 10 to 25 gallons. http://water.epa.gov/learn/kids/drinkingwater/water_trivia_facts.cfm

23. Water Facts

24. True of False? • 1: Myth – Bottled Water has more minerals • 2: Myth – Vitamin Water is better for you • 3: Fact – The Average American uses around 80 gallons of water a day • 4: Myth – Being thirsty is all down to dehydration • 5: Myth – Drinking water at night will speed your metabolism • 6: Myth – Staying in the pool means that you won’t dehydrate. • 7: Fact – We don’t use much of the Earth’s water. • 8: Fact – You need on average 2.5 liters of water per day. • 9: Myth – All bottled water comes from pure sources. http://eatdrinkbetter.com/2012/08/30/8-water-myths-and-facts/

25. Summary • The hydrogen bonding between water molecules explains many of the unique properties that make water an important substance for life. • Acids and bases change the concentration of hydronium ions in aqueous solutions. The pH of solutions in living things must be stable. • Reflection: • Using one property, describe how water makes life possible.

26. Water As a Solvent & Solutions • Water is the primary, most important medium for solutions that allowed life to develop on Earth. • A solutionis a mixture in which ions or molecules of one or more substances are evenly distributed in another substance (a fluid). • A solvent is a fluid that dissolves something. • A solute is the substance that gets dissolved. • Water dissolves many ionic and polar substances but does not dissolve non-polar substances. • Many substances are transported throughout living things as solutions of water. • Dissolved substances can move more easily within, in and out of, and between cells.

27. Solutions, Acids and Bases • Acids are compounds that form extra hydronium ions when dissolved in water. • Bases are compounds that form extra hydroxide ions when dissolved in water. • You create acids or bases by dissolving substances, such as chlorine, in water. • When acids and bases are mixed, the extra hydronium and hydroxide ions neutralize each other to form water.

28. Solutions Acids and Bases • Sometimes water dissolves itself and breaks apart to form hydronium and hydroxide ions. • In pure water, hydronium and hydroxide ions are present in equal numbers. • Acids and bases are solutions that result in different amounts of hydronium and hydroxides.

29. Solutions

30. Solutions pH and Buffers • pH is a measure of how acidic or basic a solution is. • pH is decided by how many hydronium ions are present in the solution. • Each one-point increase in pH represents a 10-fold decrease in hydronium ion concentration. • Eventually, you’ll get to the point where the concentration of hydronium ions is taken over by hydroxide ions.

31. How Do You Measure the pH of Substances? • Pure water has a pH of 7. • Acidic solutions have a pH below 7 (lots of hydronium). • Basic solutions have a pH above 7 (lots of hydroxide).

32. Solutions, continued pH and Buffers • The pH of solutions in living things must be stable. • For a stable pH to be maintained, the solutions in living things contain buffers. • A buffer is a substance that reacts to prevent pH changes in a solution. • Luckily, our blood is buffered in a bicarbonate solution so that when we eat certain foods they don’t affect our pH too much when they are broken down.

33. Employ the Knowledge • Review the video again. See if it makes more sense. http://youtu.be/HVT3Y3_gHGg

34. Group Analysis • Get into groups. • Together, work through the questions. • We will discuss with 15 minutes left in class.

35. Pre-Demonstration: Properties of Water • Pre lab questions: • What exactly do expect to happen? Write a hypothesis for this. Be specific and thorough. • We’re going to take some notes today, first we’ll watch a video.

36. Demonstration: Properties of Water • If you have washable markers (like Crayola or highlighters) get them out. • One sheet of paper per two persons (you and the person sitting next to you). • Follow directions quickly and carefully. • This is a graded “Lab/Exercise” (50 pts) that is due tomorrow. • It is homework and must be turned in 1st thing tomorrow if you do not finish.

37. Pre-Demonstration: Properties of Water Place this end in the water • Acquire a cup, a large piece of paper towel, and cut a piece of paper towel roughly 3 inches long by 2-3 inches wide. • Fill the cup up most of the way with water and carefully walk it back to your seat. • Carefully color lines across the strip of paper towel about 2 inches from one end. • One mark w/ pencil, one with pen, one with a marker. • If you press too hard you’ll cut your paper in half. • Without submerging your lines…place one end of the paper towel about an inch into the water and let the other end hang off the outer edge of the cup. • Let it sit, undisturbed, for 20 minutes. Two Inches

38. Post-Demo Analysis (50 pts.) Direction of flow • What do expect to happen? • Write a hypothesis for this. • Write what you observe & draw a picture of it. • What did the water really do? • What properties of water makes this possible? • Research your books and describe what organism uses these same principles and how.

39. Post-Demo Analysis: Properties of Water 3. Write what you observe & draw a picture of it. What did the water really do? 4. What properties of water makes this possible? 5. Research your books and describe what organism uses these same principles and how. Clean up all materials. Throw paper towels away. Dump water out and stack cups onto pile. Clean up should take less than 3 minutes.