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Glass of water metal paperclip Hydrogen Bonding of Water 012-10993 r1.04.

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Presentation on theme: "Glass of water metal paperclip Hydrogen Bonding of Water 012-10993 r1.04."— Presentation transcript:

1 glass of water metal paperclip Hydrogen Bonding of Water r1.04

2 glass of water metal paperclip Hydrogen Bonding of Water r1.04

3 The Snapshot button is used to capture the screen. The Journal is where snapshots are stored and viewed. The Share button is used to export or print your journal to turn in your work. Introduction Journals and Snapshots Note: You may want to take a snapshot of the first page of this lab as a cover page for your journal. Each page of this lab that contains the symbol should be inserted into your journal. After completing a lab page with the snapshot symbol, tap (in the upper right hand corner) to insert the page into your journal. Hydrogen Bonding of Water

4 Lab Challenges Why is water such an important molecule in nature and earth science processes? What gives water its unusual properties? For instance, how can a metal paperclip float on the surface of water? Hydrogen Bonding of Water

5 Background Water has many unique properties. These properties are derived from water's ability to hydrogen bond to neighboring water molecules. This happens because water is a polar molecule meaning it has a positive (+) side and a negative (-) side. Note: In H 2 O, more electrons surround the oxygen atoms than the hydrogen atoms, so the oxygen side of the molecule has a slightly negative charge, and the hydrogen side has a slightly positive charge. Hydrogen Bonding of Water

6 ...Background The imbalance in charge makes water molecules attract each other like tiny magnets. In a sense, water likes to "stick" to itself. This gives water a high surface tension, hence its tendency to bead up on surfaces and even support the weight of small insects (and even paperclips!) During phase changes, energy added to water must go into breaking or forming the hydrogen bonds before the water can heat up or cool down. This is called latent heat. Hydrogen Bonds Hydrogen Bonding of Water The latent heat of fusion is the energy required to freeze or melt water. The latent heat of vaporization is the energy required to boil or condense water.

7 Self-Check 1.Water molecules are able to "hydrogen bond" together because water is a _______ molecule. a)diet friendly b)covalent c)ionic d)intermolecular e)polar Hydrogen Bonding of Water

8 Self-Check 2.The energy required for the latent heat of fusion in water would go into a)melting ice to water b)freezing water to ice c)boiling water to vapor d)increasing the temperature of water e)both A and B are correct Hydrogen Bonding of Water

9 ...Background Water's unusual properties makes it important to many earth science processes. E.g., the polar nature of water allows it to wet surfaces of rocks, clays, and soil, drawing water deep into cracks and crevices and contributing to important erosion processes. Water naturally dissolves and reforms minerals and salts, carrying nutrients through the biosphere. "Mineral water" contains dissolved metals and salts important to your health! Conversely, several important molecules like carbon dioxide and oxygen can dissolve into polar water, allowing for life beneath the waves. Fish need oxygen molecules to survive—they just extract it from the water (using gills), whereas humans extract oxygen from the air using lungs. Hydrogen Bonding of Water

10 Self-Check 3. What kinds of important molecules can dissolve into water? a)carbon dioxide and oxygen b)oxygen and sucrose c)proteins and methane d)lipids and carbon dioxide e)Hot cocoa and marshmallows Hydrogen Bonding of Water

11 Water expands and rises as it turns into ice cubes! Background The polar attraction between water molecules gives water a higher heat capacity (resistance to temperature change) than most other substances. This high heat capacity moderates climates near oceans and lakes and helps organisms moderate their own temperatures. You can grab a hot pot handle briefly and not get burned, because the water in your skin cells resists temperature change. Hydrogen bonds require water to reorganize into a honeycomb shaped matrix when it freezes. The molecules in ice occupy more room than an equal amount of liquid water. This makes ice less dense than water, so it floats. It also makes water expand when it freezes. Water that squeezes into cracks and freezes will pry rocks apart, furthering the erosion process. Hydrogen Bonding of Water

12 Self-Check 4. Tony waves his hand briefly over a campfire but does not get burned. This is because the water in his skin cells has a large _________________. a)volume b)polarization c)surface area d)heat capacity e)concentration of caffeine Hydrogen Bonding of Water

13 Safety Wear safety glasses and follow all standard laboratory safety procedures. Keep water away from sensitive electronic equipment. Handle the hot plate and hot glassware in this lab with care. Do not touch with bare hands! Do not attempt to hold or move a beaker with boiling water. It can easily spill over causing serious burns. Do not allow the wires of the temperature probe to touch the hotplate at any time. Hydrogen Bonding of Water

14 Crushed ice, 300 mL Buret clamp (2) Small tripod base and rod Materials and Equipment Collect all of these materials before beginning the lab. Temperature sensor Hot plate Stirring rod Beaker 1-L Hydrogen Bonding of Water Fill with ice

15 The steps to the left are part of the procedure for this lab activity. They are not in the right order. Write the correct sequence below, then take a snapshot of this page. A. Fill glass beaker with ice. Sequencing Challenge B. Start warming the beaker and insert temperature probe to start timed collection. C. Find the freezing and boiling temperatures from your graph. D. Compare heat needed to melt ice to heat needed to warm water to a boil to heat needed to evaporate water. E. Use graph to explain what the heat from the hot plate is doing to the water molecules. Hydrogen Bonding of Water

16 Procedure 1.Turn on the hot plate, but do not put anything on it yet. 2.Connect the temperature sensor to your data collection system. 3.Fill the beaker with crushed ice (approximately 300 mL). 4.Place the temperature sensor in the ice and begin recording data while slowly stirring. 5.Collect this data for at least 30 seconds. Go to next screen while still collecting data. Hydrogen Bonding of Water

17 6.When the hot plate is completely warmed, place the beaker on the hot plate and continue stirring. 7.Stir continuously throughout the entire experiment. Partners may take turns stirring. 8.Be extremely careful not to allow the Temperature Sensor to touch the glass or to leave the surface of the ice/water. Go to next screen while still collecting data. Hydrogen Bonding of Water

18 9.Below, note time when it is obvious that the ice started to melt. Also, note time when the water has begun boiling continuously. Keep stirring! Hydrogen Bonding of Water Go to next screen while still collecting data.

19 10.Record data until the ice has melted completely and the water has been boiling for ~10 min. Stop stirring. 11.Stop the data set collection. *To Autoscale the Graph: 1.Tap to open the tool palette. 2.Tap and the graph will resize itself to fit the window. 3.Tap to close the tool palette Hydrogen Bonding of Water

20 1.Using your graph on the previous pages, enter the temperatures where ice melted and water boiled in the adjacent data table. Data Analysis Hydrogen Bonding of Water *To Enter Data into a Table: 1.Tap to open the tool palette. 2.Tap then tap a cell in the data table to highlight it in yellow. 3.Tap to open the Keyboard screen.

21 Data Analysis 2.On a separate sheet of paper, draw your own graph of the experiment. Make sure to label the overall graph, along with the X and Y axis. Include units on your axes. 3.Write 5 labels at various data points on your graph. The labels are: Heat first applied Ice completely melted Boiling started Region for latent heat of fusion (spans a range of the graph) Region for latent heat of vaporization (spans a range of the graph) Hydrogen Bonding of Water

22 Analysis 1.Which water could cause a greater burn: 10 grams of boiling water at 100ºC or 10 grams of steam at 100ºC ? Hydrogen Bonding of Water

23 Analysis 2.What does the slope of the heating curve of water depend on? Hydrogen Bonding of Water

24 Analysis 3.Why doesn’t the freezing point stay constant as the ice melts? Hydrogen Bonding of Water

25 Analysis 4.Why doesn’t the temperature of the boiling water move above 100 ºC? Hydrogen Bonding of Water

26 Analysis 5.Why does the rate of temperature change when water is melting or boiling? Hydrogen Bonding of Water

27 Analysis 6.Does solid water (ice) have the same heat capacity as liquid water? Hydrogen Bonding of Water

28 Synthesis Use available resources to help you answer the following questions. 1.What are some consequences of water expanding when it freezes? Hydrogen Bonding of Water

29 Synthesis 2.Why is it important that water has a high surface tension? Hydrogen Bonding of Water

30 Synthesis 3. Why can water act as such a good erosion agent? Hydrogen Bonding of Water

31 Synthesis 4.Where does water’s high heat capacity and large heat of vaporization come in handy for human populations? Give some examples. Hydrogen Bonding of Water

32 Multiple Choice 1.A friend wants to heat up ice until it is all evaporated. When will they have added half the energy needed to complete the job? a)Just after the ice has melted. b)When the water reaches 50° C. c)Just when the water starts to boil. d)When half the water is evaporated. e)None of the above. Hydrogen Bonding of Water

33 Multiple Choice 2.Water’s ability to wet some surfaces and not others is due to the rule that __________. a)polar molecules attract other polar molecules b)water is the universal solvent c)water will wet all surfaces d)water always seeks its source Hydrogen Bonding of Water

34 You have completed the lab. Congratulations! Please remember to follow your teacher's instructions for cleaning-up and submitting your lab. Hydrogen Bonding of Water

35 All images were taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons: steel-paperclip-in-drinking-glass-tumbler-beaker-6-AJHD.jpg.html References Hydrogen Bonding of Water


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