LABORATORY GLASSWARE AND EQUIPMENT LAB 2 Outline • • • • • • • • • • • • Welcome Reading a Meniscus Types of Glassware Reading and Recording Volumes Cleaning Glassware Digital Thermometer Using Glassware Using a Buret Using a Pipet Using a Volumetric Flask Cleanup Next Assignment Welcome • Welcome to the chemistry lab! • Chemistry is a lot of fun, but can be even more so if you are familiar with the equipment you will be using in lab. • Remember – whenever there’s glassware or chemicals out in lab, everyone has to wear goggles! Reading a Meniscus Meniscus and Parallax Types of Glassware • Graduated glassware • Volumetric (non-graduated) glassware Graduated Glassware • Beakers • Use: To contain certain volumes of solutions • Filtering Flasks • Use: To contain certain volumes of solutions • Graduated Cylinders • Use: To measure out exact volumes. • Burets • Use: To dispense exact volumes. Volumetric (non-graduated) Glassware • Volumetric Pipets • Use: To measure out exact volumes. This is the most accurate glassware in lab. • Volumetric Flasks • Use: To make up specified volumes and concentrations of solutions. Reading and Recording Volumes • We use significant figures to indicate the accuracy and precision of glassware. • Significant figures for graduated glassware are determined differently from those of volumetric glassware. Significant Figures: Volumetric Glassware • Use the Tolerance table on p. 71 to determine glassware tolerance, unless it is printed on the glassware. • For example: • The 50 mL volumetric flask has a tolerance of ± 0.05 mL. Whenever you use your 50 mL volumetric flask, you will always report two zeros after the decimal, i.e. 50.00 mL. Volumetric Flask When this volumetric flask is filled to the calibration mark, what volume should be reported? Volumetric Pipet When this pipet is used to dispense solution, what volume should be reported? Volumetric Pipet When this pipet is used to dispense solution, what volume should be reported? And to which line should the pipet be filled? Significant Figures: Graduated Glassware 1. 2. 3. Look at the glassware in question. Find the smallest graduation. Report your volume to the closest 10% of the smallest graduation. Reading Graduated Glassware Reading Graduated Glassware Reading Graduated Glassware Reading Graduated Glassware Reading Graduated Glassware Reading Graduated Glassware Smallest Graduation • A. Calculate major graduation – major graduation • B. Determine the number of spaces between two major graduations • Smallest Graduation = A / B Reading Beakers What volume should be reported? Reading Beakers • Smallest graduation: 10 mL • 10% value: 1 mL • Volume to the closest 10% of the SG: 48 mL Reading Graduated Cylinders What volume should be reported? Reading Graduated Cylinders • Smallest graduation: 1 mL • 10% value: 0.1 mL • Volume to the closest 10% of the SG: 52.8 mL Reading Burets What volume should be reported? Reading Burets • Smallest graduation: 0.1 mL • 10% value: 0.01 mL • Volume to the closest 10% of the SG: 40.05 mL Cleaning Glassware • Each student has glassware at their individual stations. Each student is responsible for the care of their glassware. • Your instructor will demonstrate the appropriate ways to: • Wash glassware with soap and a brush • Rinse glassware with tap water • Do a final rinse with very little distilled water from the distilled water faucet or from your water bottle • Dry your glassware • Return glassware to the APPROPRIATE drawer Cleaning Glassware • Now it is your turn… • Remove a 400 mL beaker from your glassware drawer. • Wash the 400 mL beaker with soap, brush, and water. • Do a final rinse with distilled water, then dry it completely. • When you are finished, add approximately 200 mL tap water to the beaker and return to your station. Using Glassware • Volume is space. The volume of a liquid, solid, or gas is the space occupied by that substance. • The base unit of volume in the metric system is the liter (L). • All of the glassware in this lab have volume measurements in milliliters (mL). • There are 1000 mL in 1 L. Using a Digital Thermometer • Carefully remove your digital thermometer from your glassware drawer. • We use digital thermometers in lab to determine the temperature of solutions. • Our digital thermometers can measure temperature in degrees Celsius (ºC) or degrees Fahrenheit (ºF). • Eventually you should be able to interconvert between these two scales. Kelvin will also be addressed in class. • Your instructor will point out all major features of this unit. Part 1: • Assemble the following equipment on your bench: • 400 mL beaker (filled with 200 mL of tap water) • digital thermometer • Determine the temperature of the tap water in your 400 mL beaker in both temperature scales. • Record these values in your lab manual. Part 2: • Read through the procedure for using a beaker, filtering flask, and graduated cylinder on page 78-79. • Assemble the following equipment on your counter: • 400 mL beaker (fill with about 200 mL of tap water) • 100 mL beaker • 50 mL graduated cylinder • 250 mL filtering flask • Medicine dropper (to bring glassware to level) • From the 400 mL beaker, fill each of the other pieces of glassware with exactly 50 mL of tap water. • Ask your instructor if you need help. • Answer the questions in your lab manual. Using a Buret • Remove a 25 mL buret from your glassware drawer. • Notice the reverse graduations on it. • Burets are used to dispense a very precise volume of solution and is therefore read differently. • Your instructor will demonstrate how to set up the buret clamp and stand. Pay close attention! • Read through the procedure for using a buret on pages 79-80. Part 3: • Now it is your turn… • Practice using the 25 mL buret by adding tap water from your 100 mL beaker and dispensing it into a 400 mL beaker. • Answer the questions in your lab manual. Using a Pipet • Most glassware is really easy to use. The pipet, however, takes a little bit of practice. • The pipet dispenses a very exact volume. • Remove a 5 mL pipet and pipet bulb from your glassware drawer. • Read through the procedure for using a volumetric pipet on pages 81-82. • Your instructor will demonstrate appropriate pipetting technique. Pay close attention! Part 4: • Now it is your turn… • Practice pipetting 5.00 mL of tap water from your 100 mL beaker and dispensing it into a 400 mL beaker. Do this several times. • Answer the questions in your lab manual. Using a Volumetric Flask • Remove a 25 mL volumetric flask from your glassware drawer. • The volumetric flask is used to make solutions of known (and accurate) concentration. • Read through the procedure for using a volumetric flask on pages 83. • Your instructor will demonstrate the proper technique for making a solution using a volumetric flask. Pay close attention! Part 5: • Now it is your turn… • Practice making a solution using a 25 mL volumetric flask. • Be sure to use the medicine dropper to fill the flask to volume. • Answer the questions in your lab manual. Part 6: • Determine the temperature of the remaining tap water at your station in both temperature scales. • Answer the questions in your lab manual. Cleaning • Carefully clean and dry all of the equipment you used today. • Glassware gets slippery when wet, so hold on! • Place your equipment / glassware in the appropriate locations in the glassware drawer. • If you are unsure of their proper location, refer to the blue binder in the bottom drawer. Next Assignment: Lab 3 • Read the required reading sections in your textbook and lab manual. • Complete and submit your pre-lab questions by the deadline. • Study for the quiz. • Turn in your Lab 2 Report for preliminary grading at the start of next week’s lab.