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Chemistry II: Properties of Water and pH Nancy Dow Kathrine Alexander

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1 Chemistry II: Properties of Water and pH Nancy Dow Kathrine Alexander
Biology Partnership (A Teacher Quality Grant) Chemistry II: Properties of Water and pH Nancy Dow Kathrine Alexander Image: 1:00 housekeeping Gulf Coast State College Panhandle Area Educational Consortium 5230 West Highway 98 753 West Boulevard Panama City, Florida 32401 Chipley, Florida 32428

2 Our approach to the standards & to this lesson
Pre-test Breaks Q & A boards Asking questions Our approach to the standards & to this lesson Pre-Test 1:15

3 Florida Next Generation Sunshine State Standards
SC.912.L Discuss the special properties of water that contribute to Earth’s suitability as an environment for life; cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent. (Moderate) Benchmark Clarifications Students will explain the properties of water at a conceptual level. Students will explain how the properties make water essential for life on Earth. Content Limits Items referring to the properties of water are limited to hydrogen bonding, polarity, cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent. Items may address adhesion but will not assess adhesion 1:30-1:35

4 Bell ringer Time Warp water droplets Time Warp water droplets
Image from: 1:35-11:42

5 Image: AHAJOKES.COM Slide 5- 12 1:42-1:57

6 THE PROPERTIES OF WATER :
Slide 5- 12 1:42-1:57 THE PROPERTIES OF WATER : Water has some very unique properties that make this molecule unlike ANY other. And we are made up of about 70% water!

7 Your body is made up of mostly of water
Your body is made up of mostly of water. Approximately 85% of your brain, 80% of your blood and 70% of your muscle is water. Every cell in your body needs water to live. Slide 5- 12 1:42-1:57

8 Unique properties of Water
Slide 5- 12 1:42-1:57 8

9 Cover page Write the book title - PROPERTIES OF WATER
Sketch and color a water molecule In the Upper right corner, write your name Slide 5- 12 1:42-1:57

10 PAGE ONE (front side) Write the Page title, POLARITY, centered at the top of the page. Draw and color (Oxygen-RED and Hydrogen- BLUE) water molecules held together by hydrogen bonds Write, bullet, and answer these questions: What is meant by polarity? Which end of the water molecule attracts most of the electrons and acts negative? Which end acts positive? How do water molecules act like “little magnets”? Slide 5- 12 1:42-1:57

11 Water is a ‘Polar Covalent’ molecule- (charges at opposite sides of molecule) ‘POLAR’ means an unequal distribution of the charge. Water is a "polar" molecule, meaning that there is an uneven distribution of electron density. Water has a partial negative charge (-) near the oxygen atom due the unshared pairs of electrons, and partial positive charges (+) near the hydrogen atoms. Is this a Covalent or ionic bond? Covalent bond because they share electrons H2O image: Hydrogen bond image: Slide 5- 12 1:42-1:57 H2O

12 HYDROGEN BOND BETWEEN WATER MOLECULES
Hydrogen bonds are very weak; heat and changes in pH, (detergents) can break these bonds. Image: Slide 5- 12 1:42-1:57 Possible water molecule manipulation

13 A Drop in the Ocean Lab 1:57- 2:10
Polar lab

14 http://www. chemistryland. com/CHM130S/13-Liquids/LiquidsSolutions
Slides 14-25 2:10- 2:30 We’ve heard that wax or oils repel water. But that isn’t true. Water is so attracted to other water molecules that anything between them is squeezed out of the way.

15 States of Water Only substance to that exists free in nature in all three states Slides 14-25 2:10- 2:30

16 PROPERTIES OF WATER WATER IS THE ‘UNIVERSAL SOLVENT’---It dissolves other “polar” molecules– a molecule that can attract a water molecule. “Like dissolves like” “polar dissolves polar” WATER MOLECULES ARE COHESIVE AND ADHESIVE---Transport of water in organisms – example: Trees Cohesion- a property of like molecules sticking together (water attracted to other water molecules” Adhesion- the tendency of dissimilar particles to cling to one another   WATER HAS A HIGH SURFACE TENSION----Water bugs walk on the surface of water FROZEN WATER (ICE) IS LESS DENSE THAN LIQUID WATER SO IT FLOATS---Keeps organisms alive in the bottom of a frozen lake WATER HAS THE ABILTIY TO MODERATE TEMPERATURE– water temperature effects coastal communities temperature Slides 14-25 2:10- 2:30

17 PAGE ONE (Backside) Write the Page title, UNIVERSAL SOLVENT, centered at the top of the page. Draw and color a solution including solvent and a solute Write, bullet, and answer these questions: What is a solvent? Why is water called a universal solvent? What is a solute? Which type of molecules, polar or nonpolar, dissolves in water? Are materials that dissolve in water hydrophobic or hydrophilic? solution Slides 14-25 2:10- 2:30

18 Universal Solvent Like a magnet that pulls on things that are magnetic, water pulls on things that are electrically charged. Magnets have north & south poles, water has positive and negative poles and thus called a polar solvent. Since unlike charges attract, the negative end of water will be attracted to the positive sodium ion. The positive end of water will be attracted to the negative chloride ion. Since water is always in motion, it will pull on the ionic compound and move the ions away from each other. This dissolves the ionic compound. Slides 14-25 2:10- 2:30 Since unlike charges attract, the negative end of water will be attracted to the positive sodium ion. The positive end of water will be attracted to the negative chloride ion. Since water is always in motion, it will pull on the ionic compound and move the ions away from each other. This dissolves the ionic compound.

19 Many compounds dissolve in water.
A solution is formed when one substance dissolves in another. A solution is a homogeneous mixture. Solvents dissolve other substances. Solutes dissolve in a solvent. Top Image: Bottom image: Solutions—a mixture that is the same throughout (homogeneous) Solvents—substance present in greatest concentration; dissolves other substances Solutes—substance present in lower concentration; dissolves in solvent The solvent is the substance that is present in the greatest amount, and is the substance that dissolves solutes. The solute is the substance being dissolved. Slides 14-25 2:10- 2:30 19

20 “Like dissolves like.” Polar solvents dissolve polar solutes.
Nonpolar solvents dissolve nonpolar solutes. Polar substances and nonpolar substances generally remain separate. Slides 14-25 2:10- 2:30 6 20

21 Common Misconceptions
Students often thinks that all solutes are solids and all solvent as are liquids. Correcting the misconception Solutions can involve different states of matter Gas in Gas- AIR: If the solvent is a gas, only gases are dissolved under a given set of conditions. An example of a gaseous solution is air (oxygen and other gases dissolved in nitrogen). Nitrogen makes up 78% of air so it’s the solvent. Gas in Liquid Stream: Oxygen in water. Liquid in Liquid Vinegar is an acetic acid solution in water (5-9 %).  Solid in solid – alloys like Steel Steel is a metal alloy whose major component is iron, with carbon content between 0.02% and 2.14% by mass. Liquid in solid: mercury in gold, forming an amalgam Air image: Stream: Vinegar Image: Steel image: Slides 14-25 2:10- 2:30

22 PAGE TWO (Front side) Write the Page title, COHESION, centered at the top of the page. Sketch and color the water droplet Write, bullet, and answer these questions: What is cohesion? Cohesion produces _____________ tension as the water molecules hold tightly together. How do living things like insects use surface tension? Slides 14-25 2:10- 2:30

23 PAGE TWO (Backside) Write the Page title, ADHESION, centered at the top of the page. Sketch and color the picture below. Adhesion pulls the liquid up the sides of the straw (capillarity). Write, bullet, and answer these questions: Define adhesion. Adhesion produces an effect called ______________ action when you place a straw in a liquid Explain how adhesion and cohesion help plants move materials. Slides 14-25 2:10- 2:30

24 Hydrogen bonds are responsible for three important properties of water.
Cohesion - water molecules “stick” to each other Adhesion - water molecules “stick” to other substances The water’s surface (left, dyed red) is curved down because the water has a greater adhesion than cohesion. The surface of the mercury (right) is curved up because mercury has greater cohesion than adhesion. 1. High specific heat— large amount of energy needed to produce an increase in temperature 2. Cohesion— water molecules “stick” to each other 3. Adhesion— water molecules “stick” to other substances Image : Slides 14-25 2:10- 2:30 Latin prefix co-together Ad- to or towards hesion 24

25 Cohesion Water’s tendency to cling together Water in space
Image: Slides 25 2:10- 2:30 When the negative end of a water molecule attracts the positive end of another water molecule, and the molecules stick together, this is called cohesion.

26 How water stacks up Image: http://www.irishviews.com/blog/tag/pennies/
Clean pennies Alcohol Medicine droppers/ water Paper towels 2:30-2:45 Lab

27 15 minutes!! 2:45- 3:00 Break!

28 Adhesion Adhesion, or capillary action, is when water molecules are attracted to other substances with a negative or positive charges. This is why water "climbs" up a piece of paper or a straw above the surface level of the water.         This figure shows water adhesion image: Slides 28-30 3:00 -3:10 Demo straw

29 Because of the cohesive properties of water, trees such as the giant sequoia are able to transport water molecules from the soil to their leaves 300 ft. above. WATER: STRONG COHESIVENESS 300 ft. Water molecule released into the atmosphere As each water molecule evaporates, it pulls additional water up through the tree because of the “sticky-ness” of the hydrogen bonds that link the water molecules. Water molecules pulled upward 6-ft.-tall man What is Life? A Guide to Biology 2010 W.H. Freeman and Co Slides 28-30 3:00 -3:10 Water molecule pulled into root system

30 Phloem and Xylem Celery lab demo Celery image: Phloem and Xylem image: Slides 28-30 3:00 -3:10 Demo celery -Phloem-Transport sugars and molecules created by the plant. Transports food made during photosynthesis. Xylem-System of tubes in a plant that transport water and dissolved minerals. The xylem distributes the water throughout the plant.

31 Surface Tension The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. The molecules at the surface do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. This forms a surface "film"  that allows insects to walk on water Slides 31-32 3:10- 3:15

32 WATER: HIGH SURFACE TENSION
Pressure applied to water surface Hydrogen bond What is Life? A Guide to Biology 2010 W.H. Freeman and Co Slides 31-32 3:10- 3:15 “V”-shaped water molecules are held together by hydrogen bonds. The bonds are just strong enough to give water a surface tension with net-like properties.

33 Trouble on the Surface Lab
3:15- 3:35 Pepper lab Image:

34 LAST PAGE (Inside of back cover)
Write the Page title, INSULATION, centered at the top of the page. Sketch and color the ice crystal. Write, bullet, and answer these questions: When is water the densest? Explain why ice floats? How is a lake or river that freezes over helpful to the organisms in the water? Slide 34-37 3:35-3:50

35 WATER: LOWER DENSITY WHEN FROZEN
because of hydrogen bonding, water is less dense as a solid than it is as a liquid. Consequently, ice floats. Water is densest at 4°C. Water contracts as it cools to 4°C. As water cools from 4°C to freezing (0°C), it expands and becomes less dense than liquid water (ice floats).  Image: Slide 34-37 3:35-3:50 Water is densest at 4°C

36 Prevents deep bodies of water from freezing solid from the bottom up.
Expansion of water contributes to the fitness of the environment for life: Prevents deep bodies of water from freezing solid from the bottom up. Since ice is less dense, it forms on the surface first. As water freezes it releases heat to the water below and insulates it. Makes the transitions between seasons less abrupt. As water freezes, hydrogen bonds form releasing heat. As ice melts, hydrogen bonds break absorbing heat. Slide 34-37 3:35-3:50

37 Thermal Expansion Thermal Expansion Lab/ Demo
Relate this to why sea level rising is not a issue because of melting ice burgs, It will be because of melting glaciers and most will be due to thermal expansion with the increase in temperature. Thermal expansion is the tendency of matter to change in volume in response to a change in temperature. thermal expansion is caused when seawater expands because of the higher temperature of the water. Since the oceans absorb heat from the atmosphere, when the atmosphere becomes warmer so will the oceans. Warm seawater has a greater volume than cold seawater. As the temperature of the ocean increases so will the total ocean volume. The increased volume will cause the level of the water in the oceans to rise THE EARTH IS GETTING WARMER The build-up of greenhouse gases, such as carbon dioxide, in the atmosphere has trapped more heat - resulting in a warmer planet. Temperatures on Earth have been rising at about 0.13°C per decade over the past 50 years. A warmer climate leads to the thermal expansion of the sea and melting of glaciers and ice caps, which lead to rising sea levels. Along with the rest of the world, Singapore experiences the effects of climate change. Slide 34-37 3:35-3:50 Thermal expansion demo

38  WATER: HIGH HEAT CAPACITY
1 Heat (energy) from the sun disrupts some of the hydrogen bonds between water molecules. 2 New hydrogen bonds are formed almost as quickly as they are disrupted. 3 Because heat energy from the sun is used up breaking and re-forming hydrogen bonds, the water temperature doesn’t increase by much. 4 Molecules that make up sand, on the other hand, don’t have so many hydrogen bonds, so the heat of the sun just increases the temperature. Disrupted bond Newly formed bond Sun WATER HAS THE ABILTIY TO MODERATE TEMPERATURE– water temperature effects coastal communities temperature Highest of all solids and liquids except liquid ammonia- prevents extreme ranges in ocean temperature – Heat transfer by currents is large Slide 38-41 3:50-4:00 Sixty percent of your body is water. This helps you to maintain a relatively constant body temperature.

39 Other unique properties of water
High boiling point oC Low freezing point- 0 oC Viscosity increases as its temperature is lowered A relatively high density to support animals with no or delicate skeletal systems Latent heat of evaporation – highest of all substances Latent heat of fusion- highest except ammonia Transparency – relatively great The boiling point of water is 100°C or 212° F at 1 atmosphere of pressure (sea level). The boiling point of water also depends on the purity of the water. Ordinarily the freezing point of water is 0° C or 32° F.  because it is low viscosity, unicellular or multicellular organisms can easily move in the water e.g. in the sea The heat of vaporization is the amount of energy required to convert or vaporize a saturated liquid (i.e., a liquid at its boiling point) into a vapor. Heat of fusion is the amount of heat required to convert a solid at its melting point into a liquid without an increase in temperature. because it is transparent, sunlight can penetrate deeper, enabling life in the deeper layers of the sea Slide 38-41 3:50-4:00

40 Why is water so important to living organisms?
Water acts as a solvent to provide a liquid environment for biochemical reactions. Water is also a transporter of nutrients, waste products, blood, and materials within cell Water dissolves polar compounds and does not dissolve nonpolar compounds. This is important for both biochemical reactions and crucial hydrophilic/hydrophobic interactions in protein folding.  Water is an important reactant in certain biochemical reactions such as electrolysis reactions and the first step of the photosynthetic electron transport chain. Water has a high specific heat capacity to facilitate better maintenance of internal temperature and the usage of evaporation to cool down. water is a main component of synovial fluid, the lubricating fluid that helps joints move smoothly and easily. Water stays liquid at high temperatures and a wider range of temperatures so that reactions can happen faster and under more diverse circumstances.  Slide 38-41 3:50-4:00

41 Follow up Q/A Board Problem solving issues in class
Additional activities Properties of Water Lab H.O.T. Water Tutorial Wonder of Water 6.5 Cloze Slide 38-41 3:50-4:00 41

42 Florida Next Generation Sunshine State Standards
SC.912.P.8.11 Relate acidity and basicity to hydronium ion and hydroxyl concentration and pH. No specific Biology standard for pH but need to understand because it is referred to in the enzymes standard as well as in reference to aquatic systems 4:00- 4:10 Slide 41-52

43 Bell Ringer Acid Bases and pH- flipped classroom Acid and base rap
Acid and base Music video

44 Acids and bases More basic More acidic Neutral
The pH is a measure of how acidic or basic a solution is. A scale with values ranging from below 0 to above 14 is used to measure pH. The origin of the term “pH” is unclear. The “H” stands for hydrogen ions; the “p” has been suggested to mean either “power” (so pH would mean “the power of hydrogen ions”) or “negative logarithm” (referring to the mathematical description of hydrogen ion concentration). 4:00- 4:10 Slide 41-52 More acidic Neutral More basic

45 Acids and bases Substances with a pH below 7 are acidic. An acid is any substance that forms hydrogen ions (H+) in water. more acidic stomach acid pH between 1 and 3 Image from Holt McDougal Florida Biology 2012 4:00- 4:10 Slide 41-52

46 A neutral solution has a pH of 7.
pure water pH 7 Holt McDougal Florida Biology 2012

47 Acids and bases Substances with a pH above 7 are basic.
A base is any substance that forms hydroxide ions (OH-) in water. bile pH between 8 and 9 more basic 4:00- 4:10 Slide 41-52 Image from Holt McDougal Florida Biology 2012

48 It is a logarithmic scale, based on powers of 10, so that 1 pH unit change equals a 10 fold change in H+ ion concentration! A pH of 6 is ten times more acidic than a pH of 7. 4:00- 4:10 Slide 41-52 The pH scale is a negative logarithmic scale, so a decrease in pH of 1 unit is actually a ten time increase in the amount of hydrogen ions.

49 pH scale is logarithmic – using powers of ten
THE pH SCALE H+ ion Water OH– ion ACIDS BASES Acids are fluids that have a greater proportion of H+ ions to OH– ions. • H+ ions are very reactive. • Strong acids are corrosive to metals. • Acids break down food in your digestive tract. • Acids are generally sour in taste. Bases are fluids that have a greater proportion of OH– ions to H+ ions. • OH– ions bind with H+ ions, neutralizing acids. • Strong bases are caustic to your skin. • Bases can be found in many household cleaners. • Bases are generally bitter in taste and soapy. Free H+ Free OH- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Battery acid Water Beer Bleach Baking soda Coffee Ammonia What is Life? A Guide to Biology 2010 W.H. Freeman and Co 4:00- 4:10 Slide 41-52 Soda Blood Soda, with a pH of about 3.0, is 100,000 times more acidic than a glass of water, with a pH of 8.0!

50 pH SCALE http://www.whoi.edu/cms/images/oceanus/phScale_99988.gif
4:00- 4:10 Slide 41-52

51 ACIDS AND BASES Acids=Free Hydrogens Bases=Free Hydroxides
4:00- 4:10 Slide 41-52 Give them the pH coloring sheet

52 times acidity or alkalinity exceeds that of pure water (7.0)
pH value times acidity or alkalinity exceeds that of pure water (7.0) Acidic 0 10,000,000 1 1,000,000 2 100,000 3 10,000 4 1,000 5 100 6 10 Neutral 7 8 9 11 12 13 Alkaline 14 A standard logarithmic scale means that two adjacent values increase or decrease by a power of 10. The pH scale is a negative logarithmic scale, so a decrease in pH of 1 unit is actually a ten time increase in the amount of hydrogen ions. A solution with a pH of 5.0 is 100 times more acidic than a neutral substance of pH 7.0 and 1,000,000 times more acidic than pH 11.0! 4:00- 4:10 Slide 41-52 Complete coloring sheet if time allows

53 How does pH affect life? pH 4:00- 4:10 Slide 41-52

54 How does pH affect enzymes?
A change in pH disrupts an enzyme's shape and structure. In general enzyme have a pH optimum. However the optimum is not the same for each enzyme. Different enzymes might have very different pH optima For example, pH can have an effect of the state of ionization of acidic or basic amino acids. Acidic amino acids have carboxyl functional groups in their side chains. Basic amino acids have amine functional groups in their side chains. If the state of ionization of amino acids in a protein is altered then the ionic bonds that help to determine the 3-D shape of the protein can be altered. This can lead to altered protein recognition or an enzyme might become inactive. Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis. In general enzyme have a pH optimum. However the optimum is not the same for each enzyme. For example in the figure below is represented a situation in which two different enzymes might have very different pH optima. The one depicted by the green curve might represent the pH optimum for the enzyme pepsin which degraded proteins (protease) in the vert acidic lumen of the stomach. The second curve (in red) might represent the enzyme carbonic anhydrase that works in the neutral pH of your cytosol. carbonic anhydrases One of the functions of the enzyme in animals is to interconvert carbon dioxide and bicarbonate to maintain acid-base balance in blood and other tissues, and to help transport carbon dioxide out of tissues. 4:00- 4:10 Slide 41-52 Green- enzyme pepsin which degrades proteins (protease) in the stomach Red- enzyme carbonic anhydrase that works in the neutral pH of your cytosol.

55 Buffers: A Mechanism to prevent pH changes—to keep the pH within normal limits because they take up excess hydrogen ions (Examples: Tums or Rolaids are buffers for stomach acidity).--- Our body has buffer systems (Homeostatic mechanisms)---Example: Buffers to keep our blood pH at 4:00- 4:10 Slide 41-52

56 Acid Base Lab Lab 4:10-4:30 Red cabbage contains a pigment molecule called flavin (an anthocyanin). This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes. Very acidic solutions will turn anthocyanin a red color. Neutral solutions result in a purplish color. Basic solutions appear in greenish-yellow. Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice. The color of the juice changes in response to changes in its hydrogen ion concentration. pH is the -log[H+]. Acids will donate hydrogen ions in an aqueous solution and have a low pH (pH < 7). Bases accept hydrogen ions and have a high pH (pH > 7). pour some of the juice into a saucer. Now comes the fun part. Sprinkle just a tiny pinch of baking soda into the juice. Watch what happens. As soon as the white baking soda hits the red cabbage juice, you get green foam. If you put in much baking soda, you will get a lot of green foam, so be ready to clean up your mess. Eventually, all of your red cabbage juice will turn green. It seems that our experiment is over, but it is not. Now it is time to get out the vinegar. Add a little vinegar to the green cabbage juice. What do you get? Pink foam! Again, there is the potential for lots of mess, so either be careful or have lots of paper towels ready. ABC Science online abc.net.au/science/surfingscientist https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcT4RARQXfoz24v8mbHwzkrLR661FOSLifSC6Re-IvO9mW3CeNYFrg

57 Cabbage juice indicator
Lab 4:10-4:30 Cabbage juice indicator

58 Follow up Q/A Board Problem solving issues in class
Additional activities pH Factor -interactive Interactive pH scale 4:30 58

59 Post Test 4:30


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