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Hydrogen, Nitrogen and Argon Chemistry

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Hydrogen, Nitrogen and Argon Chemistry Hydrogen, Nitrogen and Argon Chemistry Author: Brittland K. DeKorver Institute for Chemical Education and Nanoscale Science and Engineering Center University of Wisconsin-Madison Purpose: To learn about 3 of the gases that are in Earth’s atmosphere. Learning Objectives: 1. Understand that the atmosphere is made up of many gases. 2. Learn about the differences in flammability of nitrogen and hydrogen. 3. Learn what is produced during electrolysis. Next Generation Science Standards (est. 2013): PS1.A: Structure and Properties of Matter PS1.B: Chemical Reactions PS3.D: Energy in Chemical Processes and Everyday Life (partial) ETS1.A: Defining Engineering Problems ETS1.B: Designing Solutions to Engineering Problems ETS1.C: Optimizing the Design Solution National Science Education Standards (valid 1996-2013): Physical Science Standards: Properties and changes of properties in matter Earth and Space Science Standards: Structure of the earth system Suggested Previous Activities: Oxygen Investigation and Carbon Dioxide Chemistry Grade Level: 2-8 Time: 1 hour Materials: Safety glasses Manganese dioxide Work gloves (for handling Tea-light candles steel wool) Matches Test tubes Spatulas Beakers Wooden splints 100mL graduated cylinders Waste bucket for burnt 15mL graduated cylinders materials 3% hydrogen peroxide Vinegar Baking soda Safety: 1. Students should wear safety glasses during all activities. 2. Students should not be allowed to use matches or candle. 3. Students should be cautioned to only mix the chemicals as directed. Introduction: Air refers to the mixture of gases that make up the Earth’s atmosphere. In this lesson, students will learn about hydrogen (present in very, very small amounts in our atmosphere), nitrogen (the most prevalent gas), and argon (third behind nitrogen and oxygen.) Procedures: 1. Investigating Hydrogen – Electrolysis of Water a. Students must wear goggles. Help them perform the following instructions. See below for student handout. b. You will need: i. 2 pencils with both ends sharpened ii. 2 wires with alligator clips on both ends iii. 1 9-volt battery iv. 1 glass vial v. Tape vi. Salt vii. Baking soda viii. Water c. Fill the beaker three-quarters full with water. d. Fill the vial entirely with water. e. Carefully put your finger over the mouth of the vial and hold it upside down. Slowly lower the vial into the beaker until just the mouth is under water. If you get an air bubble in the vial, try again. f. Tape the vial upside down against the side of the beaker. g. Use a balance and a weigh boat to add 1 gram of salt and 1 gram of baking soda to the beaker. h. Clip one end of each wire to the battery. i. Clip the other end of each wire to the pencil. Make sure the alligator clip is touching the gray pencil lead, not the wood. DO NOT TOUCH THE TWO PENCIL LEADS TOGETHER. j. Put the other ends of the two pencils in the beaker. k. Position the tip of the pencil that is attached to the – side (negative terminal) of the battery under the vial. l. Observe the results. m. When the vial is full of gas, remove the pencils from the beaker. n. Place your finger of thumb over the mouth of the vial. o. Take the vial to a lit candle and carefully hold it over the flame. p. If time/materials allow, repeat steps a-m, but in step k, put the pencil that is attached to the + side of the battery under the vial. Note any differences in flame test. 2. Investigating Nitrogen – DEMONSTRATION ONLY a. Students must wear goggle and stand back at least 10ft. from liquid nitrogen. Erect a barrier (table, chairs, etc.) so that they are not permitted to come forward. b. Place a cafeteria tray to protect the surface of the table. c. Light a tea-light candle and place in the center of the tray. d. Slowly pour a small amount of liquid nitrogen behind the candle (so that the candle remains visible to the students). e. Continue pouring until the candle is extinguished. 3. Effects of Temperature on Volume of Gases – DEMONSTRATION ONLY a. Students must wear goggle and stand back at least 10ft. from liquid nitrogen. Erect a barrier (table, chairs, etc.) so that they are not permitted to come forward. b. Place a cafeteria tray to protect the surface of the table. c. Place an air-filled balloon in two nested plastic tubs. d. Pour liquid nitrogen over the balloon. e. Allow students to make observations. 4. Argon a. Allow the students to observe the argon sample (blue neon sign). 5. Carbon Dioxide and Nitrogen a. Ask the students to think about whether carbon dioxide and nitrogen have the same mass. b. Guide the students in devising a way to test the question. c. Have students do investigation and summarize the results. Discussion: Hydrogen In Oxygen Investigation, students learned that water is made up of hydrogen and oxygen atoms in a 2:1 ratio. They have produced and tested oxygen gas via catalyzed hydrogen peroxide decomposition. The electrolysis of water produces both hydrogen and oxygen gas (H2 and O2) through an electrochemical reaction. The stored energy of the battery is used to pull electrons from the oxygen (the oxidation half-reaction) and give them to the hydrogen (the reduction half reaction), creating elemental oxygen and hydrogen. Hydrogen is a flammable gas. Once the vial is full of hydrogen (after 15-20 minutes) students can perform the flame test on the hydrogen. It will make a small whoosh or “woof” noise. Be sure to caution students to listen carefully and be quiet when performing flame test, or they may miss the noise. Students can repeat the procedure with the positive terminal, which will produce oxygen gas, which will cause a flame to flare, but will not produce any explosions or sound. Ask students whether they think there is a lot of hydrogen in air. If they seem unsure, remind them that it is possible to have lit candles, bonfires, etc. without having an explosion in the presence of air. Ask them to compare this with how much oxygen they believe is in the air. Again, remind them that burning and explosions can take place in the air without additional oxygen sources. Nitrogen During the flame test demonstration, remind the students about the fire triangle. Ask which components are being removed from the candle by the nitrogen. Ask questions about the fog and reinforce the concepts in the dry ice component. During the balloon demonstration, describe volume as the space that molecules occupy and explain the relationship between temperature and energy. Tell the students that when gas molecules have less energy, they move closer together. Ask students to predict what will happen when the balloon warms, and ask them to provide reasoning for their answers. Argon Argon is the third most prevalent gas in our atmosphere. It is an inert gas (one of the Noble gases) and is not reactive. However, when an electric current passes through it, the electrons of argon absorb some of the energy and release it as visible light. Other elements exhibit similar behavior. Evaluation: What two atoms make water? What is the ratio? Is the air we breathe only oxygen or a mixture of gases? Name two elements present in air. Is argon a reactive gas? This lesson is the product of the Institute for Chemical Education and the Nanoscale Science and Engineering Center at the University of Wisconsin-Madison. This Material is based upon work supported by the National Science Foundation under grant number DMR-0425880. SCIENCountErs Lessons are licensed under a Creative Commons Attribution- NonCommercial 4.0 International License. Permissions beyond the scope of this license may be available by emailing [email protected]. .
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