Name: Hour: Teacher: ROZEMA / CHEMISTRY. Molecular Attractions

Transcription

1 Name: Hour: Teacher: ROZEMA / CHEMISTRY Molecular Attractions

2 Name: Hour: Teacher: Ms. Rozema Starter Questions Grading: 2 pts = Date and full question written, question answered. 1 pt. = one requirement missing. 0 pts = no Q or A If you have an excused absence, write ABSENT and get the question from a classmate. Answer the question yourself. Date Copied Question & Best Attempt At Answer Points Paraphrase/Write the Question: 0 Answer: 1 2 Paraphrase/Write the Question: 0 Answer: 1 2 Paraphrase/Write the Question: 0 Answer: 1 2 Paraphrase/Write the Question: 0 Answer: 1 2

3 Name: Hour: Teacher: Ms. Rozema Starter Questions Grading: 2 pts = Date and full question written, question answered. 1 pt. = one requirement missing. 0 pts = no Q or A If you have an excused absence, write ABSENT and get the question from a classmate. Answer the question yourself. Date Copied Question & Best Attempt At Answer Points Paraphrase/Write the Question: 0 Answer: 1 2 Paraphrase/Write the Question: 0 Answer: 1 2 Paraphrase/Write the Question: 0 Answer: 1 2 Paraphrase/Write the Question: 0 Answer: 1 2

4 SUMMARY NOTES

5 SUMMARY NOTES

6 Molecules and Not Molecules Purpose: In this lesson, you will look at a few things you come in contact with often and determine what the features are of things that are considered as molecules. Remember from the last unit that the picture for Molecular Covalent bonding model looks like this: 1. What do the spheres represent? 2. What do the gray areas represent? Station 1, Water, H 2 O 3. Sketch the model and the drawing of the water molecules in the box here. 4. How many ATOMS are in one water MOLECULE? List the types and numbers of atoms in each water molecule: H = O = 5. What do you think the lines or connectors are that hold the atoms together? How do you think they relate to the Molecular Covalent bonding picture?

7 Station 2, Ethyl Alcohol, C 2 H 6 O 6. Sketch the model and the drawing of the ethyl alcohol molecules in the box here. 7. How many ATOMS are in one ethyl alcohol MOLECULE? List the types and numbers of atoms in each water molecule: C = H = O = 8. When hand sanitizer (ethyl alcohol) evaporates from your hands, do you think the alcohol molecules break apart into individual C s, H s, and O s, or do they stay together as ethyl alcohol? Why do you think this? Station 3, Sodium Chloride, NaCl 9. Do your best to sketch the model of the sodium chloride in the box here. 10. What type of bonding model is this (look at the types of elements in the formula)? 11. How is the structure of NaCl similar or different from other molecules?

8 Station 4, Ammonia, NH Sketch the model and the drawing of the ammonia molecules in the box here. 13. How many ATOMS are in one ammonia MOLECULE? List the types and numbers of atoms in each water molecule: N = H = 14. How is the molecule of ammonia, NH 3 different from the picture of Molecular Covalent bonding shown here? Station 5, Chalk, Calcium Carbonate, CaCO Do your best to sketch the model of the calcium carbonate in the box here. 16. What type of bonding model is this (look at the types of elements in the formula)? 17. What other substance in this lab is the structure of CaCO 3 most similar to?

9 Boiling Pre-Discussion Flora is boiling water on a stove. She turns the temperature dial up to medium-high, just enough to get the water boiling. The water is boiling gently with bubbles slowly but visibly forming at the bottom and popping at the surface. Flora then turns the dial of the stove up to high to get the water vigorously boiling. The water is now forming large bubbles, which are bursting at the surface. Flora wonders if the boiling temperature changes when she turns the dial. What would you tell Flora? A. The boiling temperature is greater when the dial is set at high. B. The boiling temperature is greater when the dial is set at low. C. The boiling temperature is the same at both settings. Thinking on Your Own 1) For each person, write an explanation why someone might think this would happen. A: B: C: 2) Pick which explanation you think is most likely to be true. Write the person here. Is there anything you would add to your explanation in #1? 3) For each of the two statements you did not pick, write why you think they are incorrect. Describe any evidence you think would prove these statements incorrect.

10 With your neighbor 1) Carefully listen to your neighbor s prediction and write it down here: 2) How is your neighbor s prediction similar/different to your own? Listen for details in the explanation, not just the overall answer. Explain the Results 1) Did you predict what was going to happen to the temperature in the water? 2) Write an explanation for what we observed happening to the temperature of the water. 3) Based on what we saw and what you have learned, what is happening to the molecules of water when you are boiling it? 4) Nitrogen, N2, is a molecule that weighs a little more than water (one molecule of N2 weighs 28 amu whereas one molecule of water weighs 18 amu). However, nitrogen boils at a much lower temperature of -196 C. What is it about nitrogen that you think makes it boil at such a low temperature?

11 Boiling Points Name Formula Mass Boiling Point Propanone (Acetone) C 3H 6O C Butane C 4H C Butanone C 4H 8O C Butyl alcohol C 4H 10O C Ethyl alcohol C 2H 6O C Pentane C 5H C Pentanone C 5H 10O C Propane C 3H C

12 Propyl alcohol C 3H 8O C Ethane C Ethanal C 1. What are some general observations you have about the data? These are statements such as I see that the -one molecules all have (this is a good entry-point statement for those 2. What patterns do you see in the data that involve the boiling points? What evidence do you have from the table to back up these patterns? 3. What factors in the molecules do you think influence the boiling points? What evidence do you have from the table to support your thinking?

13 Name Formula Mass Boiling Point Propanone (acetone) C 3H 6O C Pentane F C 5H C A Butane B C 4H C Pentanone G C 5H 10O C Butanone C C 4H 8O C Propane H C 3H C Butyl alcohol C 4H 10O C Propyl alcohol C 3H 8O C D I Ethyl alcohol E C 2H 6O C Ethane J C Ethanal C K

14 Attractive Molecules Attractions Between Molecules Purpose To observe the response of certain liquids to an electrical charge and the behavior of the same liquids as droplets. Part 1: Testing the Liquids With your partner, place one drop of the liquid onto the lab benchtop. Enter the results in the table. Once you have the drops on the bench top, use your packet to fan the droplets until they start evaporating. Do this until one or two of your drops are totally evaporated and record your data. Then, using the dropper, carefully see how many drops of water and ethyl alcohol you can fit onto a penny. Compound Structure Drop behavior on bench top Water, H2O # of drops on a penny How fast do the drops evaporate? Propanone, C 3H 6O Do not do this Isopropyl Alcohol, C3H8O Do not do this Ethyl alcohol, C2H6O Part 2: Analysis 1. What evidence do you have that some molecules are held more strongly together (with other molecules) than others? For instance, if you compare water and isopropyl alcohol, which substance would you say is held more strongly together? Why?

15 2. The picture below is trying to show what water molecules might look like as they are clumped together on top of a penny. Draw what you think the picture would look like when the water molecules fall off the penny. 3. What kind of bonding hold the oxygen and hydrogen together in water (think about the bonding models and the types of elements hydrogen and oxygen are). 4. Do you think the bonds holding the hydrogen and oxygen together are the same ones that hold the water droplets on top of the penny? Why or why not? 5. Shown here are a molecule of water and a molecule of ethyl alcohol. Write a few hypotheses for why the two molecules behave the way you observed based on their molecular structure.

16 6. What do you think is holding the droplets of water together on top of the penny? Why do you think ethyl alcohol behaves differently than water?

17 Boiling Point (K) Patterns: Intermolecular Forces and Boiling Point Table 1: Boiling points and masses of various alcohols. Name of alcohol Formula Mass Boiling point Amount of increase in boiling pt. Propanol C 3H 8O K XXXXX Butanol C 4H 10O K Pentanol C 5H 12O K Table 2: Boiling points and masses of various ketones. Name of keytone Formula Mass Boiling point Amount of increase in boiling pt. Acetone C 3H 6O K XXXXX Butanone C 4H 8O K Pentanone C 5H 10O K Table 3: Boiling points and masses of various acids. Name of acid Formula Mass Boiling point Amount of increase in boiling pt. Propanoic Acid C 3H 6O K XXXXX Butyric Acid C 4H 8O K Pentanoic Acid C 5H 10O K Mass 1. On the graph shown, label the y-axis with the appropriate numbers. 2. Using a closed circle,, graph the mass vs. the boiling point of the ALCOHOLS.

18 3. Describe how the boiling point changes as the mass of each alcohol increases. Be specific in terms of how much the boiling point increases by. 4. Put an open circle where you believe an alcohol with 2 carbons would be. 5. Using a closed triangle,, graph the mass vs. the boiling point of the KETONES. 6. Describe how the boiling point changes as the mass of each alcohol increases. Be specific in terms of how much the boiling point increases by. 7. Put an open triangle where you believe a ketone with 2 carbons would be. 8. Using a closed square,, graph the mass vs. the boiling point of the ACIDS. 9. Describe how the boiling point changes as the mass of each alcohol increases. Be specific in terms of how much the boiling point increases by.

19 10. Put an open square where you believe an acid with 2 carbons would be. 11. Suppose you have a compound that contains 2 carbon atoms. You discover that it has a boiling point of 390 K. Do you predict that this compound is an alcohol, ketone, or acid? Use the patterns you figured out in questions 4, 7, and 10 to justify your answer by looking at the amount of increase in boiling points.

20 Thinking (Electro)Negatively Electronegativity Scale Purpose To explore numerical values for electronegativity and to learn how to use them to compare atoms and bonds. Questions: Use the Electronegativity Scale to answer these questions. 1. What happens to the electronegativity values across each period from left to right? 2. What happens to the electronegativity values of each group from bottom to top? 3. If you have a bond between a metal atom and a nonmetal atom, which of the two is more electronegative? Explain your thinking.

21 4. Where are the atoms with the greatest electronegativity values located? Are they metals, nonmetals, or metalloids? 5. Where are the atoms with the lowest electronegativity values located? Are they metals, nonmetals, or metalloids? 6. Why do you think the noble gases do not have electronegativity values? 7. Circle the atom in each pair below that will attract shared electrons more strongly. C or Cl Rb or Br I or In Ag or S As or Na H or Se 8. Which two atoms from the periodic table would form the most polar bond? Why did you choose these two elements? 9. List at least three examples of pairs of atoms with nonpolar covalent bonds. Look back at your notes or Polar Bears and Penguins if you are not sure. 10. Why are the bonds listed in #9 considered nonpolar covalent?

22 11. If the difference in electronegativity between two bonded atoms is greater than 2.1, then the bond is considered to be ionic. List three examples of pairs of atoms with ionic bonds, showing the electronegativity values. An example as been done for you. K Cl, Cl = 3.16, K = = If the difference in electronegativity between two bonded atoms is less than 2.1, then the bond is considered to be polar covalent. List three examples of pairs of atoms with polar covalent bonds, showing the electronegativity values. 13. Metal atoms tend to form cations with positive charges. Based on the definition of electronegativity, is the fact that metals forming cations consistent with their electronegativity values? Why or why not? (Think about what a big electronegativity means compared with a small electronegativity) 14. Sulfur forms both ZnS and SF2. Is sulfur the most electronegative element in both compounds? Why or why not? Show the electronegativity values in both compounds?

23 15. Arrange these bonded pairs in order of increasing polarity from the least polar to the most polar. Show the electronegativity values and differences in each of these bonds. C H H O N H H F 16. Explain how you would use the electronegativity scale to determine both the direction and the degree of polarity (how polar it is) of a bond between two atoms. 17. Which of these pairs of atoms would result in the most electronegative bond? The least electronegative bond? Arrange them in order from the least polar to the most polar. C H C S H F C N C O H Br

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28 Polar Bears and Penguins Electronegativity and Polarity Purpose To understand polarity and bonding between atoms. Instructions Read the comic strip The Bare Essentials of Polarity, and use it to answer these questions. 1. How does the comic strip define a polar molecule? 2. Define electronegativity as you understand it, after reading the first two pages of the comic strip. 3. What is the artist trying to represent by two polar bears arm wrestling or two penguins arm wrestling? 4. What three types of bonds are represented on the third page of the comic strip? What happens to the bonding electrons in each type of bond?

29 5. Explain why there are four scoops of ice cream in the illustration of the O2 on Page What about the six scoops of ice cream in the illustration of N2 on Page 4? 7. Describe what you think is happening to the penguin in the CO2 molecule in the picture on the fourth page. 8. Name three things that the picture of CO2 on Page 4 illustrates about the molecule. 9. Describe what you think is happening to the penguins in the illustration of H2O on Page What does the crossed arrow represent in the comic strip?

30 11. What are two of the definitions of dipole given in the comic strip? 12. What does electronegativity have to do with polarity? 13. If you finish early: Using polar bears and penguins, create an illustration showing a hydrogen sulfide molecule, H2S. (Hint: You might want to start with a Lewis dot structure.)

31 Potential Energy Boiling Points (Computer Lab Work) Polar and Nonpolar Boiling Points Purpose To explore the boiling points of different substances using a PhET Simulation. Instructions: 1. Open Google Chrome. Type in PhET States of Matter. 2. Click on Run Now. If the Java popup asks you to update Java, click on Later. 3. Click on the Phase Changes tab at the top of the screen. Questions: Part 1: Make sure Neon is clicked, and that you are in Kelvin temperature. 1. You should be at a temperature of 13 K. What state of matter are you in? how do you know? 2. Sketch the Mountain-Valley-Hill diagram for Neon. Label the curve for Neon. Distance Between Molecules

32 3. Gradually heat up Neon until it turns into a liquid. To do this, heat it up until the RED DOT on the graph reaches the point where it first touches the liquid area. What temperature did Neon approximately melt at? 4. Now, heat up Neon until it starts to turn into a gas. To tell it s a gas, look at the molecules, and heat it up until least 4 atoms of Neon have broken free from the blob of neon. What is this phase change called? What temperature did this happen? 5. Based on what you have been learning in class, is Neon a polar or nonpolar substance? Why do you think this? 6. Based on what you have been learning, what is holding Neon together as a solid and a liquid? What forces are you overcoming as you heat up Neon to turn it into a gas? Hit Reset All. Change the simulation to look at Oxygen, O2. 7. On the same graph as #2, sketch the Mountain-Valley-Hill curve for Oxygen. Based on the graph, will Oxygen require more energy or less energy to melt it? How do you know? 8. Be sure the temperature starst at or below 31 K. Gradually heat up Oxygen until it turns into a liquid (look at the picture with the RED DOT). What temperature did Oxygen approximately melt at?

33 9. Now, heat up Oxygen until it starts to turn into a gas. To tell it s a gas, look at the molecules, and heat it up until least 4 molecules of oxygen have broken free from the blob of oxygen. What temperature did this happen? Did it take more energy or less energy to boil Oxygen than it did for Neon? How do you know? 10. Based on what you have been learning in class, is oxygen, O2, a polar or nonpolar substance? How do you know? 11. Based on what you have been learning, what is holding oxygen together as a solid and a liquid? What forces are you overcoming as you heat up oxygen to turn it into a gas? Hit Reset All. Change the simulation to look at Water, H2O. 12. On the same graph as #2, sketch the Mountain-Valley-Hill curve for Water. Based on the graph, will water require more energy or less energy to melt it? How do you know? 13. Be sure the temperature starts at or below 157 K. Gradually heat up Water until it turns into a liquid (look at the picture with the RED DOT). What temperature did Water approximately melt at? What is the actual melting point of water in Celsius? In Kelvin? (Look it up if you need to)

34 14. Now, heat up Water until it starts to turn into a gas. To tell it s a gas, look at the molecules, and heat it up until least 4 molecules of water have broken free from the blob of water. What temperature did this happen? Did it take more energy or less energy to boil water than it did for oxygen? How do you know? 15. Based on what you have been learning in class, is water, H2O, a polar or nonpolar substance? How do you know? 16. Based on what you have been learning, what is holding water together as a solid and a liquid? What forces are you overcoming as you heat up water to turn it into a gas? 17. The picture below shows water molecules as a LIQUID. Draw dashed lines showing the forces that must be overcome to become a GAS. Then draw a picture of water molecues as a gas. Water as a gas 18. Do you agree or disagree with the following statement: Water, H2O, takes more energy to boil than oxygen, O2, because the bonds between hydrogen and oxygen are stronger in water than the bonds between the oxygen atoms in O2. Explain why you agree or disagree.