Basic Laboratory Techniques Name: ___________________________________ Block: ______ Introduction Laboratories can be very complex and a little intimidating. In this lesson, you will learn about some basic laboratory techniques that will build your confidence by teaching you how to pour, measure, filter, and use gas burners and glassware. When you first set foot inside a chemistry lab, it can be a little overwhelming. There are chemicals in bottles, flame sources, and all kinds of fragile glassware. Learning the proper techniques and how to use all the equipment can take time, but we all must start with the basics. Lab techniques are the processes and practices that are recommended for using various equipment in the laboratory. In this lesson, we will go over some of the most basic lab techniques you will need to know. Pouring and Measuring Pouring is a technique that is used in everyday life, and spills and splatters are common. We've all seen somebody try to pour a glass of water and make a mess all over a counter top. When it comes to pouring substances in a laboratory, the technique must be much more precise. The basic technique to pouring liquid in a lab is using a stirring rod, or another similar instrument. You use the stirring rod to connect the pouring spout from the source container to where you want the liquid to go. Because liquids, especially water, are cohesive and tend to attach themselves to solid materials, using a stirring rod allows the liquid to flow smoothly down the rod without spilling. When pouring a liquid without a stirring rod, it is recommended to hold the two containers at arm’s length with your elbows slightly bent. To measure the volume of a liquid using a graduated cylinder, or other calibrated and marked container, place your eye along the level of the liquid. You will see something that resembles a bubble shape along the top of the liquid with a top and bottom line. This is called the meniscus. The bottom of the meniscus should be lined up with the markings on the side of the graduated cylinder for an accurate measurement. Gas Burners and Heating Gas burners are connected to a gas supply through rubber tubing. After the gas flow is turned on, the burner is lit with a match or burning splint. Gas burners can be adjusted by opening or closing an air vent, which increases or decreases the amount of air that enters the burner. The vent should be closed when the burner is first lit. This will produce a yellow flame. As the air vent is opened, the flame will become increasingly blue, and therefore increasingly hot. It's important to never reach over a burner, and to keep hair and loose clothing secured when using a gas burner. When heating substances using glassware, it is important to use special, heat-resistant glassware. Also, put a piece of wire gauze between the flame and the glass to avoid direct contact. When heating material in a test tube, the tube should always be held using a special test tube holder or clamp, with the opening of the test tube pointed away from everyone present. Cleaning equipment Once chemicals have been properly disposed of, the glass (or plastic) equipment should be washed using soap, water, and correct sized wire brush. When soap is completely rinsed out with tap water, rinse again using distilled water. With a constant stream of distilled water, go around the inside at the top of the equipment one to two times, swirl water around, then pour water down the drain. Allow to air dry. Lab Each piece of lab equipment has a specific function and purpose. In the following experiments, you will need to use each piece of equipment correctly. Your task is to obtain the correct lab equipment, chemicals, and supplies. You are to follow the experiment instructions precisely and complete each experiment. Once each experiment has been completed, properly dispose of chemicals, clean equipment, and return everything to the area you obtain it. The first few experiments are very simple but will teach you how to use and read the equipment, so make sure you start with the first experiment listed. The following experiments will continue to teach you how use equipment, but tend to be more interesting. As you learn the correct procedures, you may start to notice that not every little detail is included, such as, you may not be told to use weigh paper to weigh out chemicals. These are details and skills that is assumed. For example, when your mom tells you to brush your teeth, you automatically know how to spit the toothpaste out of your mouth. Also, it’s very important that you do not change the order of experiments, they build upon each other. After each experiment, answer all questions in the lab and give as much detail as possible. Don’t forget to be careful, precise, and wear your goggles! Experiment 1: Accuracy of Graduated Cylinder Materials (one of each unless specified): Scale 100 mL beaker 100 mL graduated cylinder Micropipette 30 Pennies Procedure: 1. Using tap water from the sink, fill a 100 ml beaker to the 50 ml mark. Be careful, the water will spray out of the nozzle with great force. Turn the faucet nozzle as slowly as possible to reduce splattering water. 2. Pour the water in the 100 ml beaker into the 100 ml graduated cylinder (which is more accurate than the beaker). 3. How accurate was your beaker measurements? 4. Add or take away water to correct the 50 ml of water in the graduated cylinder. (You may need to use the micropipette to slowly change the water level). 5. On the electronic scale, weigh out 30 pennies and record your measurement in the table below. 6. Carefully, drop the pennies into the graduated cylinder that contains 50 ml of water. Read and record your measurements. 7. Pour out the water to retrieve pennies. The water may be poured down the sink, 8. Complete the table by finding the density of the pennies. (D = m/v). 100 ml Beaker and Graduated Cylinder Mass of pennies Volume of Cylinder & pennies Penny volume (volume of cylinder and pennies – 50 mL) Penny density 9. In the box below, draw a picture of a meniscus curve shown in the graduated cylinder. 10. Clean up lab space and return all equipment and materials. Meniscus curve drawing: Experiment 2: Pouring liquids in apparatus Materials (one of each): Ring stand Utility clamp 100 mL Beaker 150 mL Beaker 50 mL Burette Glass stirring rod Funnel Micropipette Procedure: 1. Connect utility clamp to the ring stand. 2. Place an empty 150 ml beaker in the middle of the base of the ring stand where the burette will be hanging over it. 3. Insert 50 ml burette into the utility clamp above the beaker. Make sure the bottom of the burette is high enough so you can open and close it easily with no solution splattering out of the beaker. 4. Add 50 ml of tap water into 100 ml beaker. 5. Using the beaker only, pour approximately 15 ml of water into burette. If you over fill the burette, you can open the spout of the burette to release the additional water. Use micropipette if needed. Remember the meniscus curve!! 6. Using the beaker and glass stirring rod, pour approximately15 ml of water into burette. Place a third of the glass rod into the burette. Place the lip of the beaker to the glass rod and slow pour water onto the glass rod. If you over fill the burette, you can open the spout of the burette to release the additional water. Use micropipette if needed. 7. Using the beaker and funnel, pour approximately 15 ml of water into burette. Place the funnel into the burette and pour water into the funnel. If you over fill the burette, you can open the spout of the burette to release the additional water. Use micropipette if needed. 8. Clean up lab space and return all equipment and materials. All water can be poured down the drain. Questions: Which was the easiest procedure for you to use and why? If you were using corrosive solutions (solutions that will burn you if it comes in contact with your skin), which procedure would you feel most comfortable in using? Experiment 3: Measuring out solutions using a Erlenmeyer flask Materials (one of each unless specified): Erlenmeyer flask Scale Weigh boat Scoopula Glass stirring rod 100 mL graduated cylinder Micropipette 17.5 grams of glucose Water (for this experiment, we will use tap water but in most cases distilled water is used) Procedure: 1. Plug in and turn scale on. 2. Place weigh boat on scale and click “tare” or “zero” button to zero out the scale. 3. Measure out 17.5 grams of glucose. Use scoopula to transfer glucose from the container to the weigh boat. 4. Record (on line below) the exact amount of glucose measured out. a. Weight of glucose __________________________________ (make sure you write the exact weight shown on scale) 4. Take weigh boat with glucose and pour the glucose into an Erlenmeyer flask. Make sure you pour in all the glucose. Don’t leave any in the boat. 5. Fill 100 ml graduated cylinder with 100 ml of tap water. 6. Using glass stirring rod, pour water into Erlenmeyer flask. 7. Swirl Erlenmeyer flask until glucose has completely dissolved. 8. Congratulations, you have now created your first solution! 9. Pour solution down the sink with plenty of water, clean up lab space, and return all equipment and materials. Stoichiometry (Conversion) Problem: Figure the molarity of your solution. Fill in the blanks of the following stoichiometry problem. In General Chemistry, you will learn how to write your own stoichiometry problem. ________ g of glucose x ________ mL of H O 2 Fill in the blanks 1 mole x 58.8 g glucose 1000 mL = __________mole = 1 Liter 1 Liter Calculate 1 mole Liter Experiment 4: Rapid Color Changing Chemistry Materials: All liquids should be measured using graduated cylinders. Mortar and pestle Beakers 1 – 100 mL 3 – 250 mL Graduated cylinders 1 – 10 mL 1- 25 mL 1 – 100 mL Micropipettes Thermometer Hot Plate Glass stirring rod Tongs 1000 mg Vitamin C Iodine (2%) Hydrogen peroxide (3%) Liquid laundry starch Paper towel Procedure: 1. Place mortar and pestle on top of a paper towel. 2. Crush the 1000 mg Vitamin C tablet by placing it into the mortar and using the pestle push down and twist on the tablet. Continue until the tablet is powder. 3. Place a 250 ml beaker of water onto a hot plate and heat between 40⁰-50° C. Maintain the temperature. 4. Liquid A: Place the Vit. C powder into a 100 ml beaker. Add 60 ml of warm water. Stir for at least 30 seconds. 5. Liquid B: Measure out 5 ml of liquid A into 250 ml beaker. Add 60 ml of warm water and 5 ml of iodine to the beaker and mix. 6. FYI: You are now done with liquid A, you may put it aside. 7. Liquid C: In another 250 ml beaker, mix 60 ml of warm water, 15 ml of hydrogen peroxide, 2.5 ml of liquid starch. 8. Pour all liquid B into liquid C. Then Pour the combined liquid back and forth between the two beakers a few times. Once completed, place the beaker with the liquid down on the table and observe….be patient. Questions: 1. What was the exact temperature of your “warm” water? 2. When you added the iodine to the liquid A, what color did the brown iodine turn? 3. At the end of the experiment, what happened to the final liquid?