Lab Protocols

Filtering a solid out of a liquid is done using filter paper and a filter funnel. The filter funnel is supported by the ring on a ring stand. Lay a clay triangle across the ring, then place the filter funnel into the triangle. filter paper To prepare the filter paper, fold the paper in half , then fold it in half again. When you look at the open edge of the folded paper you will see four edges of paper. With thumb and finger, catch three of these edges. Squeeze the sides of the folded paper and a cone will form with three thicknesses of paper on one side and one thickness of paper on the other. Place this cone of paper into the filter funnel. Place a "catch container" under the stem of the filter funnel and adjust the height of the ring on the ring stand until the tip of the stem is below the mouth of the container. Use a wash bottle and wet down the inside of the filter paper. This will help it stick to the funnel. You are now ready to filter. Carefully pour the liquid ...

Many chemistry experiments require something to be heated. This is done with one of several types of laboratory burners. The lab burners at Mt. Lebanon High School use methane gas delivered through the gas outlets at student lab stations. a proper lab burner flame Before attempting to light any lab burner, check to see that the jet hole between the base and the burner tube is free of obstruction. If chemicals have covered this jet, the burner will not operate properly. After attaching the hose to the gas outlet, turn the handle on the outlet parallel to the nozzle to open the gas valve. The gas valve is turned off by turning the handle 90 degrees in either direction. Carefully check to see that you hear gas escaping from the mouth of the burner tube. When you are sure that you have gas, bring the head of the striker over the burner and squeeze the striker handle. The spark produced will ignite the gas and your burner is lit. Adjust the air control vent so that the flame has the proper...

The triple-beam balance was once the "standard" balance in the general chemistry lab. While the electronic balance has replaced it in many cases, good science students should be familiar with the triple-beam balance and how to read one. a triple-beam balance The balance is named for its three "beams". An object is placed on the pan of the balance and tares on the beams are moved to balance the mass. As you face the balance, the back beam is graduated in 10 gram steps and the middle beam is graduated in 100 gram steps. It is very important that the tares on these two beams are in the notch for the whole number of grams and not in between notches. The front beam is a sliding scale graduated in grams. The tare on this beam can be positioned anywhere on the scale. Masses on a triple-beam balance can be read to tenths of a gram, and estimated to hundredths. Clicking on the balance picture will give you a close view of the position of the tares on the three beams. What m...

The electronic balance has many advantages over other types of balance. The most obvious is the ease with which a measurement is obtained. All that is needed is to place an object on the balance pan and the measurement can be read on the display to hundredths of a gram. an electronic balance A second advantage, using the Zero button on the front of the balance, is less recognized by beginning science students. Because one must never place a chemical directly on the balance pan, some container must be used. Place the container on the balance and the mass of the container will be displayed. By pressing the Zero button at this point, the balance will reset to zero and ignore the mass of the container. You may now place the substance to be weighed into the container and the balance will show only the mass of the substance. This saves calculation time and effort. However, when the container is removed from the balance, the display will go into negative numbers until the Zero button is pres...

Pipettes are much more accurate than graduated cylinders. Reading the volume of liquid in a pipette is just like reading a graduated cylinder, however there is one additional technique needed with a pipette. The diameter does not allow a liquid to be poured into a pipette - the liquid must be drawn into the pipette. regular bulb on top and safety bulb on bottom This picture shows two of several types of pipette bulbs used to draw a liquid into a pipette. The red bulb is known as a standard pipette bulb. The black bulb is known as a safety pipette bulb. Much of the "professional" lab work today is done with automatic pipettes. These are expensive little gadgets that come in many different volumes, each delivering exactly its assigned volume with one click of a button. High school chemistry students need to know the basic techniques of pipetting, so you will be using glass pipettes and the standard pipette bulb. The standard pipette bulb requires manual dexterity that is imp...

The surface of a liquid confined in a cylinder curves to form what is known as a meniscus. The meniscus of most liquids curves up the sides of the container, making the center of the curve appear lower than the edges. Mercury is one of very few exceptions - it curves down at the edges. Since reading the meniscus at the top or at the bottom of the curve will make a difference in the volume measured, it is generally agreed to always read the bottom of the curve. The smaller the container, the greater the curve of the meniscus. Pictured below is the meniscus in a 10 mL graduated cylinder. To gain experience in reading liquid volumes, click on the picture to enlarge it and read the volume in the following way: the meniscus in a graduated cylindar 1. The largest graduations on this graduated cylinder are numbered, representing milliliters. What whole number of milliliters are represented in the picture? 2. There are five graduations from one major line to the next in this picture. In ot...