Hydrogen Oxygen Generators

Transcription

1 Hydrogen Oxygen Generators Adapted from: Author: Doris Pun & Brittland DeKorver Institute for Chemical Education and Nanoscale Science and Engineering Center University of Wisconsin-Madison Purpose: To learn about energy and alternative forms of energy Learning Objectives: 1. Combustion reactions with oxygen and gasoline are the basis of engines 2. Ethanol and hydrogen are alternative fuels Next Generation Science Standards (est. 2013): PS1.A: Structure and Properties of Matter (partial) PS1.B: Chemical Reactions PS3.A: Definitions of Energy (partial) PS3.D: Energy in Chemical Processes and Everyday Life ESS3.A: Natural Resources ESS3.C: Human Impacts on Earth Systems National Science Education Standards (valid ): Standard B: Physical Science o Properties and changes in properties of matter o Transfer of energy Standard D: Science and Technology o Abilities of technological design o Understanding about science and technology Standard F: Science in Personal and Social Perspectives o Science and technology in local, national, and global challenges Grade Level: 2-8 Time: 60 minutes Preparation ahead of time: Cut off the tapered stems of several plastic pipets just below the bulb. Materials: Piezo Popper Kit (from Educational Innovations #HS- 2A) Plastic film canisters Safety glasses Gloves 3% hydrogen peroxide (H2O2) Manganese dioxide (MnO2) 1.0 M HCl

2 Zinc pieces Pipettes/stirrers Scissors Test tubes Rubber stoppers Tubing Large bowls Cups Dirt and/or salt, food coloring Plastic wrap Calculators with solar cells (will be disassembled) Optional: device with wind generator Safety: Wear gloves and safety goggles while handling the hydrogen peroxide and hydrochloric acid, HCl. Safety goggles must be worn in assigned launching area. Hydrogen peroxide and hydrochloric acid should not be mixed together. Introduction: Burning gasoline or regular fossil fuels is important for heating our homes, running our cars and powering most of what the world s population needs everyday. However, fossil fuels are limited and produce greenhouse gases. An alternative is burning ethanol, in particular ethanol distilled from corn crops. Biomass is another source of ethanol fuel. Hydrogen can also be burned to generate electricity. Other common types of alternative energy are solar, wind, nuclear, and geothermal (utilizing hot water or steam from the Earth s interior). Tell the students that today they are going to learn about alternative forms of energy by making rockets powered by ethanol or hydrogen gas. They will also be able to experiment with solar cells and generators. Procedures: 1. Solar Distiller a. Fill the bowl with 1 inch of water b. Add dirt, soil and/or food coloring and stir c. Place empty cup upright in middle of bowl d. Wrap bowl tightly with plastic wrap (use tape if necessary) e. Place bowl in sunny place (or under light source) f. Observe after 45 minutes 2. Solar Cells a. Take apart solar powdered calculators to see how they work 3. Ethanol Fueled Rockets a. Assemble film canister-sparker according to instructions in kit b. Add 2 drops of ethanol to the film canister c. Put lid on the canister d. Shake and warm in hands e. Aiming away from people, shoot film canister by pushing injector button

3 4. Hydrogen Fueled Rockets Only mentors should build the hydrogen and oxygen generators! a. Demonstrate for students how to fill a pipet bulb entirely with water. Demonstrate how to hold the pipet bulb upright and fill via water displacement. Allow students to practice. b. Hydrogen generator i. The mentor should place 3-5 pieces of mossy zinc in a test tube. ii. The mentor should fill a test tube with 1M HCl, leaving enough room at the top for a rubber stopper. iii. The mentor will stopper the test tube with a rubber stopper connected to a small length of tubing, which is connected to the tapered stem of a pipet. c. Oxygen generator Mentor only! i. The mentor should half fill a test tube with hydrogen peroxide. ii. The mentor should add a small amount (about the size of a grain of rice) of manganese dioxide to a test tube. The mentor should fill a test tube with 3% hydrogen peroxide, leaving enough room at the top for a rubber stopper. iii. The mentor will stopper the test tube with a rubber stopper connected to a small length of tubing, which is connected to the tapered stem of a pipet. d. Filling the rocket i. The student should place their water-filled pipet bulb over the tapered pipet stem of either the hydrogen or oxygen generator and allow it to partially fill. ii. The student should then continue to fill the bulb with the other gas (hydrogen or oxygen) until just a small amount of water (about 1/3 to 1/4 of the bulb) remains. This water acts as a plug to keep the gases in and also will serve as a propellant for the rocket. The bulb must be held upright at all times to prevent the water and gases from escaping. e. Firing the rocket i. The student should place the ends of a Piezo electric sparker into the pipet bulb, above the line of the water. The student should push the igniter. Discussion (simplify explanations to younger students): For the Piezo popper rockets, the methanol, CH3OH, is burned in the presence of oxygen, O2, from the atmosphere, producing carbon dioxide and water, releasing energy, which shoots the film canister several feet in the air. CH3OH + 3/2 O2 -> CO2 + 2H2O + energy This reaction is reminiscent of burning gasoline, usually CnH2n+2 (example octane gasoline: n=8),

4 C8H O2 -> 8 CO2 + 9 H2O + (energy x 8) but produces and releases more molecules of carbon dioxide into the atmosphere, but also releases 8 times more energy per unit of methanol. Ethanol fuel, which is similar to methanol, is often referred to as a cleaner burning fuel and championed as the greener fuel to use in cars but according to the above chemical reaction equations, there really is no difference. The emission of unclean chemicals from the normal gasoline is really due to the nitrogen- and sulfur-containing chemical contaminants also present that burn and produce smog and other air pollutants. In the hydrogen generators, the students observe the chemical reaction of hydrochloric acid, HCl, with zinc metal, Zn, which generates hydrogen, H2, which also releases energy. Zn + 2 HCl -> ZnCl2 + H2 + energy The hydrogen reactions refers to the use of either gasoline or water to produce hydrogen, which is used as the fuel. Hydrogen burns in the presence of oxygen to form water, producing water and electricity. H2 + ½ O2 -> H2O This process is clearly the cleanest since no carbon dioxide is produced and released into the ozone. However, energy is required to generate the hydrogen in the first place. Evaluation: Have student complete the worksheet. 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 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 ing ice@chem.wisc.edu.

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