Construction of a Simple Gas- Delivery Apparatus SCIENTIFIC Demonstration Procedure Introduction Collect gases for classroom study using this simple, inexpensive gas-delivery apparatus. Concepts • Generation of gases • Pressure and vacuum Materials Bent glass tubing Medicine dropper, glass piece only Cork borer, 12–20 mm diameter One-hole rubber stopper, size 10 Gas generator bottle or flask Pinch clamp Glycerin Plastic freezer bag, quart size Hydrochloric acid, 3 M (optional) Thistle tube Latex or rubber tubing, ~ 24 inches Two-hole rubber stopper, size 10 Marble chips, calcium carbonate, CaCO3 (optional) Vacuum pump or aspirator Safety Precautions Check all connections and carefully follow directions—generating gases in a closed system can be very hazardous. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Please review current Material Safety Data Sheets for additional safety, handling, and disposal information for all chemicals used to generate gases. Procedure Construct the Gas-Delivery Apparatus 1. Use a large, sharpened cork borer to cut a large hole (12–20 mm) in a size 10, one-hole rubber stopper. The result is a stopper with a plug that can be removed (the plug has the original single hole in it). 2. Remove the plug from the stopper and push the plastic freezer bag through the hole in the stopper, leaving about 1 inch of the bag sticking out of the opening. Push the bag through the hole so the bag opening is on the larger side of the stopper (Figure 1). 3. Place the smaller, one-hole stopper “plug” into the freezer bag opening. The freezer bag should now be held tightly between the walls of the two stoppers (Figure 2). 4. Carefully insert the tapered end of a medicine dropper through the small hole in the stopper plug. To do this, place a drop or two of glycerin in the hole and carefully work the dropper back and forth until the tip is inside the bag (Figure 3). #10 Stopper Medicine dropper Freezer bag Freezer bag opening Freezer bag Stopper plug One-hole stopper plug Figure 1. Side View Figure 2. Top View Figure 3. Gas-Delivery Apparatus © 2016 Flinn Scientific, Inc. All Rights Reserved. Publication No. 10527 1 061616 Construction of a Simple Gas-Delivery Apparatus continued 5. Attach a short piece of latex tubing over the top end of the medicine dropper and place the pinch clamp on the latex tubing. 6. Evacuate the gas-delivery apparatus: Remove the pinch clamp and attach the latex tubing to either a vacuum pump or an aspirator. When the bag has been evacuated, replace the pinch clamp on the tubing. Generating a Gas Gases are available in convenient lecture bottle and refillable cylinder sizes. Consult your current Flinn Scientific Catalog/ Reference Manual for a complete listing of gas sources and supplies, including regulator valves. Alternatively, assemble the fol- lowing apparatus for generating carbon dioxide gas. 7. Set up a gas generator using a “gas generation bottle” or a flask equipped with a gas delivery tube, as shown in Figure 4. Note: The “Gas Generation Bottle” available from Flinn Scientific (Catalog No. AP1558) includes the bottle, two-hole stopper, thistle tube, and bent glass tubing. 8. Place marble chips in the gas generator bottle. 9. Carefully pour 3 M hydrochloric acid through the thistle tube until the acid level in the flask is at least 1 cm above the bot- tom of the thistle tube stem. A vigorous reaction will begin immediately. 10. Purge the air from the gas generator system: Allow the gas to escape into the atmosphere or under water for 1–2 minutes before filling the gas-delivery apparatus with carbon dioxide (steps 11–13). Filling the Gas-Delivery Apparatus 11. Attach the end of the latex tubing to a gas source or to the bent glass tubing on the gas generator bottle. Quickly remove the pinch clamp. 12. Slowly and carefully, fill the gas-delivery apparatus with gas. The bag should be taut when filled, but not ready to burst. 13. Remove the latex tubing from the gas source and quickly replace the pinch clamp. The gas-delivery apparatus now contains a slightly pressurized sample of gas. 14. The gas-delivery apparatus may be used to fill syringes with gas for various gas-law and equilibrium experiments. Disposal Save all materials for future use. Connecting to the National Standards This laboratory activity relates to the following National Science Education Standards (1996): Unifying Concepts and Processes: Grades K–12 Systems, order, and organization Constancy, change, and measurement Content Standards: Grades 9–12 Content Standard B: Physical Science, structure and properties of matter, chemical reactions Materials for Construction of a Simple Gas-Delivery Apparatus are available from Flinn Scientific, Inc. Catalog No. Description AP1558 Gas Generation Bottle Consult your Flinn Scientific Catalog/Reference Manual for current prices. 2 © 2016 Flinn Scientific, Inc. All Rights Reserved. .