1. Lesson 4 Laboratory Glassware and Equipment
Objectives:
* The student will learn names and functions for common types of laboratory equipment.
* The student will be able to use an electronic balance to determine mass.
* The student will be able to use a triple beam balance to determine mass.
* The student will be able to use a graduated cylinder to determine volume.

2. I. Equipment
a. Beaker – a piece of glassware in which the opening diameter is approximately the same as the base diameter.
i. It is used to hold liquids, and sometimes solids.
ii. Graduations on the sides are approximate.
iii. These should never be used for measuring volumes, unless you are specifically told you only need an approximate amount.

3. b. Flask
i. Erlenmeyer Flask – a piece of glassware with the opening diameter significantly smaller than the base diameter. The diameter gradually narrows from the base up to near the top.
1. It is used for holding liquids.
2. It is resistant to splashing when mixing liquids.
3. Graduations on the sides are approximate.

4. ii. Florence Flask – a piece of glassware with the opening diameter significantly smaller than the base diameter. The bottom of the flask is generally rounded, with a long, narrow neck.
1. It is used for holding and mixing liquids.
2. The bottom is sometimes flat, and sometimes completely rounded (and will not stand up on its own)
3. Often used in organic chemistry experiments.
4. Not usually graduated.

5. iii. Volumetric Flask – a piece of glassware with the opening diameter significantly smaller than the base diameter. The bottom is usually rounded, and there is a line drawn on the next approximately halfway up.
1. It measures an exact amount of a liquid, to two decimal places. (for example, mL)
2. It is used for mixing specific concentrations of solutions.
3. To use:
a. Fill approximately half full with the solvent.
b. Add the solid (solute) to the solvent.
c. Mix to dissolve most of the solid.
d. Add solvent until the meniscus is sitting on the line in the next portion of the flask.

6. c. Balance
i. Triple-Beam Balance – a mechanical balance used to determine the mass of an object, by moving sliders on three bars until the mass on the pan is balanced by the positions of the sliders.
1. When not in use, and the sliders are at the right side of their tracks, the pointer should be exactly on zero.
2. If it needs adjusted, turn the knob under the pan slowly until it reads 0.
All readings made by this balance must be reported to 2 decimal places.

7. Common Pitfalls
Students often confuse mass and volume, their units, and the devices used to measure them. Keep the following information fresh in your mind:
Mass Volume
Grams (g) Milliliters (mL)
Balance Graduated cylinder
Always keep these two straight!

8. ii. Electronic Balance – a balance used to determine the mass of an object. If it is at zero when turned on, the mass can be determined simply by placing the object on the pan and reading it.
1. Make sure the pointer on the screen is indicating grams, or it is measuring in the wrong units.
2. If it does not read zero after turning it on, wait for the reading to stabilize, then press the “Tare” button to zero it.
3. All readings made by this balance must be reported to 2 decimal places.

9. Analytical Balance – a balance used to determine the mass of an object to a high degree of precision.
1. Readings made by this balance must be reported to decimal places.
2. Because of its high degree of precision, the pan is enclosed in a chamber to eliminate the effect of air currents in the room on the reading.

10. iv. General rules
1. Always weigh objects on a piece of weighing paper, or in a disposable weighing tray.
a. Place the piece of weighing paper on the balance.
i. If using the triple-beam balance, determine the mass of the paper and record it in your data table.
ii. If using the electronic balance, when the reading is stable, press tare.
b. Place the material to be massed on the paper or in the tray.
c. Record the reading of the balance.
d. Take your material off of the balance, clean anything left behind, and reset the balance to zero for the next person.
2. Never place anything heavier than the capacity of the balance on the pan.
3. Never weigh anything which is too hot to hold in your bare hands.

11. Common Pitfalls
One common request made in a lab exercise is to obtain “approximately” so much of a chemical. This can be an approximate mass or an approximate volume. When you obtain chemicals requested in this manner, don’t spend a lot of time getting very close to the specified amount. It is more important to measure accurately how much you got than to get very close to the requested amount.

12. d. Graduated Cylinder – a piece of glassware that is used to determine the volume of a liquid.
i. A graduated cylinder is the only piece of glassware which can be used to accurately determine the volume of a liquid.
ii. Choose a graduated cylinder which is appropriate for the amount of liquid you are measuring.
iii. Always read the volume from the bottom of the meniscus.
1. Meniscus – a curved, “contact-lens”-like shape which forms at the surface of a liquid in a container.
2. It forms because of the attraction or repulsion between the liquid and the molecules which make up the sides of the container.
iv. The measurements from a graduated cylinder should be reported to the correct number of decimal places, with the last digit being an estimate.
v. The plastic ring which is around the neck of the cylinder is a safety device to keep it from breaking if it tips over. Leave this in the upper 1/3 of the cylinder.

13. e. Burette – a glass tube, similar to
e. Burette – a glass tube, similar to a graduated cylinder in that it is graduated and designed to measure the volume of liquids. However, a burette requires something to hold it upright, such as a burette clamp, and also has a spigot on the bottom of it.

14. f. Ruler/Meter Stick – a piece of equipment used to determine the length of an object.
i. Make sure when using these pieces of equipment that you have an accurate “zero” starting point.
ii. If you do not, use another point as your “zero”, and subtract your initial starting point from your final reading.
iii. Most meter sticks and rulers read to 0.01 cm. This includes 1 digit that is an estimate.

15. g. Vacuum Filtration Apparatus
i. Filtering Flask – also known as a sidearm flask, which is used for collecting the filtrate during a filtration.
ii. Aspirator – a tube which attaches to the faucet of the sink, and creates a vacuum in the attachment when water is running through it.
iii. Filtervac – a black rubber disk used to create a seal between the filtering flask and the funnel.
iv. Buckner Funnel – a funnel with a flat bottom where filter paper is placed, and holes to allow the filtrate to pass through.

16. Ring Stand – a heavy metal base with a pole sticking up, used to attach objects to during experiments. The weight attached to the pole MUST be over the base to avoid instability.
Metal Ring – a ring with a clamp to attach it to the ring stand, used to support objects during an experiment.
Pipestem Triangle (clay triangle)– a triangle of wire, with the center pieces surrounded by tubes. This is used to support a crucible during an experiment.
k. Crucible/Lid – a small porcelain cup and lid used to heat small amounts of material directly over a flame.

17. l. Wire Gauze – a piece of wire with a center circle of a heat-resistant material, used for diffusing heat from a flame or setting hot objects on.
Evaporating Dish – a small porcelain bowl used for heating materials in to drive off the liquid portion.b
Watchglass – a round, concave piece of glass, used to mix small amounts of materials.
o. Bunsen burner – a flame-generating device, with self-contained controls for the amount of gas and air proceeding to the reaction.

18. Beaker tongs – these are tongs used for holding or carrying a beaker, and are coated with rubber to keep from scratching the glassware. They must NEVER be used to hold things in a flame.
Crucible tongs – these are metal tongs used to hold a crucible. They may be used to hold other hot objects, and can be used to transfer things into or out of a flame, as they have no coating.
r. Wash bottle – this is a bottle which contains distilled water, and is used to transfer this water into a reaction or to clean things.

19. s. Pipette – there are several kinds of these, but all are small tubes used for measuring out or transferring liquids. Some have graduations, and some have self contained bulbs.
Ring Stand Thermometer Clamp – a double clamp which is designed to attach to a ring stand with one clamp, and hold a thermometer between the small gold fingers on the other end.
u. Burette Clamp – a double sided clamp which is designed to hold burettes. There are several varieties in use in our lab, but all are of a similar

20. Ring stand test tube clamp – a clamp used to attach to a ring stand and hold a test tube.
w. Striker – a device used to create sparks which are used to light a Bunsen burner.

21. Other equipment on your check-in list not described in your notes:
Test tube rack and test tubes
Adjustable ring stand clamp
Wire test tube holder
Gold double clamp
Stirring rod with rubber policeman
Petri dish
Dropper bottle
Plastic utility pan

22. II. Measurement
a. In taking and recording measurements using various devices, it is important to pay attention to both what units are required and the number of decimal places and significant figures produced by that device.
b. Significant figures will be covered at another time.
c. Each measuring device is designed to measure a specific number of digits with certainty, and one estimated digit.
d. In estimating the last digit, break the given unlabeled space into tenths, and assign a value.

23. 13 cm 14 cm The 13 and the .4 are certain
The 5 is an estimate of the distance between the 4th and 5th tick mark, since the arrow appears to be halfway in between the two marks. An estimate of 4 or 6 in this case would also be correct.
This measurement would be cm.

24. This measurement would be 6.80 cm.
e. Examples:
i. Ruler
6 cm cm
The 6 and the .8 are certain
The 0 is an estimate of the distance between the 8th and 9th tick mark, An estimate of 1 or 2 in this case would also be correct.
This measurement would be 6.80 cm.

25. 9 mL 8 mL ii. Graduated cylinder
Remember to read from the bottom of the meniscus.
The 8 and the 6 are certain, where the 0 is an estimate since the meniscus appears to be right on the line.
This volume would be recorded as 8.60 ml.
ii. Graduated cylinder
9 mL
8 mL

26. This is an unusual scale, similar to our 25 mL graduated cylinders
This is an unusual scale, similar to our 25 mL graduated cylinders. The smaller marks represent half the distance between the two larger marks, and not all of the larger marks are labeled. The proper measurement for this volume would be 5.6 mL. The 5 is certain because the mark is above the 5.5 mL tick mark, and the 6 is estimated. 5.7 mL would also be an acceptable estimation. In this case, you are not expected to estimate tenths between the marks, because you are given “halfway” markers. In a sense, you could perform the same measurements without the smaller marks being present.

27. In the case of the triple beam balance, there are several sliders
In the case of the triple beam balance, there are several sliders. The larger mass sliders lock into place, so there is no estimation involved in their use. You just need to be sure they are locked into their slot. The single gram slider is read in the same way you would read a ruler. For the final reading, the values of the three sliders are added together. In this case, 200g + 50g g = g. Notice how the reading has 2 decimal places, just like the ruler above did g or g would also be acceptable.

28. 2. Describe a beaker, and draw a sketch of one.
Questions:
1. (In Class) Write three possible measurements for each of the following devices, making sure to have the correct number of digits and the correct units with each measurement.
a. Triple Beam Balance
b. 100 mL G.C.
c. 50 mL G.C.
d. 25 mL G.C.
e. 10 mL G.C.
f. Electronic Balance
g. Meter Stick
2. Describe a beaker, and draw a sketch of one.
3. Describe the three different kinds of flasks.
4. Describe the differences between three kinds of balances.
5. Describe how to mass an object on a triple-beam balance.
6. Describe how to mass an object on an electronic balance.
7. Describe the four parts of a vacuum filtration setup.