Lab 1: LABORATORY PROCEDURES Lab Safety and Techniques

Honors Chemistry

Lab 1: LABORATORY PROCEDURES – Lab Safety and Techniques

Name ___Period______Dates______

Please note: This lab is a one week lab worth 85 points. It will be graded for completion and accuracy. It is due on Tuesday, September 2nd, many of the questions that are not readily apparent when conducting the lab are answered in the A Special Message on Safety packet. This is the only lab that you will not put in a lab notebook. Instead, after it is graded and returned, you should save it in your binder and use it as a reference

Introduction:

The best way to become familiar with chemical apparatus is to actually handle the pieces yourself in the laboratory. This experiment is divided into several parts in which you will learn how to adjust the gas burner, use a balance, handle solids, measure liquids, filter a mixture, and measure temperature and heat. Great emphasis is placed on safety precautions that should be observed whenever you perform an experiment and use this apparatus. Several useful manipulative techniques are also illustrated throughout this lab and in A Special Message on Safety. In many of the later experiments, references will be made to these sketches and procedures. You will also be referred to many of the safety precautions and procedures explained in all parts of this experiment. It is important that all students develop a positive approach to a safe and healthful environment in the laboratory.

OBJECTIVE

After completing this experiment, you should be able to use laboratory equipment safely and skillfully.

Safety

Take the necessary safety precautions before beginning each part of this experiment. Always wear safety goggles, apron and closed-toe shoes when in the laboratory. Get into the ‘good habit’ of always putting on this standard safety equipment as soon as you enter the lab. It is important that you and your partner observe all safety precautions while conducting experiments. Read all safety precautions while conducting experiments.

PART 1 THE BURNER

Apparatus

Heat Resistant Mat

Crucible tongs

Burner

Evaporating dish

Materials- located in hood

Matches

Copper wire, 18 gauge

Special message on safety: In addition to goggles, aprons, and closed toe shoes, all long hair must be tied back, and loose clothing removed or secured out of the way when using a burner. Be sure to follow instructions and do not leave the gas jet on when burner is not lit.

Procedures

The Bunsen or Tirrell burner is commonly used as a source of heat in the laboratory. Although the details of construction vary among burners, each has a gas inlet located in the base, a vertical tube or barrel in which the gas is mixed with air, and adjustable opening or ports in the base of the barrel. These ports admit air to the gas stream. The burner may have an adjustable needle valve to regulate the flow of gas. In some models the gas flow is regulated simply by the flow of gas. The burner is always turned off at the gas valve on the supply line, never at the needle valve. Look at Figure 1-1 as you examine your Bunsen burner and locate these parts. You must know what happens to the flame when you increase or decrease the gas and when you open and shut the air intake. Be sure to take note what happens to the flame as you adjust your burner. Also, all lab partners must be able to light the burner and adjust the burner, so everyone should practice.

Figure 1-1

CAUTION

Before you light the burner, check to see that you and your partner have taken the following safety precautions against fires: Wear safety goggles, and aprons. Confine long hair and loose clothing: Tie long hair back at the back of the head away from the front of the face, roll up long sleeves on shirts, blouses and sweaters away from the wrists. You should also know the locations of fire extinguishers, fire blanket, safety showers, and sand buckets and how to use them in case of a fire.

In lighting the burner, partially close the ports at the base of the barrel, light the match. Hold the lit match just below the top of the barrel. Turn the gas full on and slowly raise the lit match toward the top of the barrel. The gas flow may be regulated by adjusting the gas valve until the flame has the desired height. If a very low flame is needed, remember that the ports should be partially closed when the gas pressure is reduced. Otherwise, the flame may burn inside the base of the barrel. When improperly burning in this way, the barrel will get very hot, and the flame will produce a poisonous gas, carbon monoxide.

Special note: Carbon monoxide is a poisonous gas. If the flame is burning inside the base of the barrel, immediately turn off the gas at the gas valve. Do not touch the barrel of the burner, for it is extremely hot! Allow the barrel of the burner to cool off and then proceed as follows: Begin again, but first decrease the amount of air admitted to the burner by partly closing the ports. Turns the gas full on and then relight the burner. Control the height of the flame by adjusting the gas valve. By taking these steps, you should acquire a flame that is burning safely and is easily regulated throughout the experiment.

Once you have a flame that is burning safely and steadily, you can experiment by completely closing the holes (ports) at the base of the burner. Describe what the flame looks like when the ports are completely closed.

Using the crucible tongs, carefully hold an evaporating dish in the tip of the flame (underside to the flame) for about 3 – 5 minutes. Place the dish on the ceramic pad, allow the dish to cool, and then examine the underside. Describe the results and suggest a possible explanation for this observation.

Such a flame is seldom used in the laboratory. For laboratory work, you should adjust the burner so that the flame will be free of yellow color, nonluminous, and also free from the ‘roaring’ sound caused by admitted too much air.

Regulate the flow of gas to give a flame extending roughly 8cm above the barrel. Now adjust the supply of air until you have a quiet, steady flame with a sharply defined, light blue inner cone. This adjustment gives the highest temperature possible with your burner. Using the crucible tongs, inset a 10-cm piece of copper wire into the flame just above the barrel. Lift the wire slowly up through the flame. Where is the hottest portion of the flame located?

Hold the wire in this part of the flame for a few seconds. Observe both the flame and the wire. Describe the results of each.

Shut off the gas burner. Now think about what you have just observed in procedures 4-6. Why is the nonluminous (blue) flame preferred over a yellow luminous flame in the laboratory?

Each lab partner needs to practice lighting the burner. If during the course of this procedure each person did not have a turn. Take a moment and allow the other lab partners to practice lighting the burner. Also, if time allows, heat the bottom of the soiled evaporating dish in a nonluminous flame to clean it. (It will be very difficult to clean it by washing, so if necessary, put it away and clean by heating another day.)

At the end of this part of the experiment, all equipment you store in the lab locker or drawer should be completely cool, clean, and dry. It should also be arranged in an orderly fashion for the next lab experiment. Check to see that the valve on the gas is completely shut off. Remember that hands should always be washed thoroughly with soap at the conclusion of each laboratory period.

PART 2 HANDLING SOLIDS

Apparatus

Test Tube

Spoon

Materials – in hood

Magnesium Sulfate MgSO4

Weigh paper

CAUTION

Do not touch chemicals with you hands. Some chemical reagents readily pass through the skin barrier into the bloodstream and can cause serious health problems. Some chemicals are extremely corrosive.
Always wear gloves, apron, and safety goggles when handling chemicals.
Carefully check the label on the reagent bottle or container before removing any of the contents.
Never use more of a chemical than directed.
You should also know the locations of the lab shower and eyewash and how to use them in case of an accident.

CAUTION

Never try to pour a solid from a bottle into a test tube. Never try to put chemicals into a test tube with a spoon. The chemicals could miss and touch your hands, or you would need to clean them up of the table.
As a precaution against contamination, never pour unused chemicals back into the reagent bottles.

CAUTION

Never discard broken glassware into the wastepaper basket. This is an important safety precaution, and it prevents personal injuries to anyone who empties the wastepaper basket. All glass must be discarded in the broken glass container.
Never discard chemicals in the wastepaper basket or sink unless told by your teacher to do so. This is an important safety precaution against fires and toxic waste being disposed of inappropriately. Discard chemicals in the proper containers in the hood, unless instructed to do something else.

Solids are usually kept in wide-mouthed bottles. A porcelain or plastic spoon should be used to dip out the solid. See figure 1-2.

Remove a small spoonful of magnesium sulfate from its reagent bottle. In order to transfer the magnesium sulfate to a test tube, first place it on a piece of weigh paper about 10 cm square. Roll the paper into a cylinder and slide it into a test tube that is lying flat on the table. When you lift the tube to a vertical position and tap the paper gently, the solid will slide down into the test tube.

Give two reasons why it is important to use this method of transferring solids into a test tube.

______

Set the magnesium sulfate aside, and continue on with Part 3.

PART 3 THE BALANCE

Apparatus

Electronic Balance

Spoon

Materials – in hood

Magnesium Sulfate MgSO4 (from part 2)

Weigh paper

Procedures

When a balance is required for determining mass, we will most often use an electronic balance (shown to the left). Depending on the accuracy required we will use either an electronic balance that records mass to 0.01 or 0.001 Each lab station is also equipped with a centigram balance (shown to the right). The centigram balance is sensitive to 0.01 gram.
The centigram balance should only be moved by grasping under the carriage base center support, and gently lifting it off of the table. NEVER grab the balance by the beams. The electronic balance and supporting them from the bottom.

Before using the centrigram balance, always check to see if the pointer is resting at zero. If the pointer is not at zero, check the slider weights. If all the slider weights are at zero, turn the zero adjust knob until the pointer rests at zero. The zero adjust knob is usually located at the far left end of the balance beam. Whenever weighing chemicals, always use weighing paper or a glass container.

NEVER place chemicals or hot objects directly on the balance pan. They can permanently damage the surface of the balance pan and affect the mass weighing

Thanks to a generous grant, we have 5 electronic balances to use in our honors chemistry lab. You will find electronic balances more convenient to use than the centigram balance.

CAUTION

Do not touch chemicals with you hands.
Always wear safety goggles and apron when handling chemicals.
Carefully check the label on the reagent bottle or container before removing any of the contents.
Never use more of a chemical than directed.
You should know the locations of the safety shower and eyewash and how to use them in case of an accident.
Never place hot glass or chemicals in your lab drawer as this could cause a fire.

Place the electronic balance on a flat, stable surface, and check to see that it is plugged in. The precision of the balance relies on minute factors and wind, shaky surfaces, or similar forces will cause the readings to be inaccurate.
Press the "ON" button and wait for the balance to show zeroes on the digital screen.
Obtain a piece of weigh paper and place it on the balance pan. Record the mass of the weigh paper to the nearest 0.01g. ______
Using a spoon, or by carefully pouring, add the magnesium sulfate you set aside from PART 2 on to the piece of weigh paper that is on your balance pan. Record the mass.______
What is the mass of the magnesium sulfate you have? ______
Remove the weigh paper and magnesium sulfate and set it aside.
Ensure your balance reads zero.
Place a new piece of weigh paper on the balance platform.
Press the "Tare" or "Zero" button to automatically deduct the weight of the container from future calculations. The digital display will show zero again, indicating that the container's mass is stored in the balance's memory.
Remove the weigh paper and notice the reading in the digital display. Place the weigh paper back on the balance pan, notice the reading on the digital display. Describe what is going on?______
With the weigh paper on the balance pan, carefully add the magnesium sulfate to the weigh paper, until you have 5 grams.
Throw the magnesium sulfate into the labeled waste container in the hood. All weigh paper should be thrown into the regular garbage cans. Clean off your lab table.

Note, some lab procedures will ask you to mass the container and record that value, and then record the mass of the container and the substance, and record that value as we did in steps 8-10. If this is the case you would not use the “Tare” (Using the Tare feature allows you to know the mass of the substance without doing any mathematical calculations. This is a helpful feature when a lab calls for a specified mass of a substance.)

CAUTION

Never discard chemical or broken glassware into the wastepaper basket. This is an important safety precaution against fires, and it prevents personal injuries to anyone who empties the wastepaper basket.
As a precaution against contamination, never pour unused chemicals back into their original bottles.

PART 4 FILTRATION

Apparatus

Ring stand

Stirring rod

Ceramic center, wire gauze

Evaporating dish

Matches

Burner

Wash Bottle

Filter paper

Iron ring

Funnel

Materials

Water

Fine Sand

Procedures

Sometimes liquids contain particle of insoluble solids, present either as impurities or as precipitate formed by the interaction of the chemicals used in an experiment. If the particles are insoluble and denser that water, they soon sink to the bottom. Most of the clear, supernatant (swimming above) liquid may be poured off without disturbing the precipitate. Such a method of separation is known as decantation. The soluble salts are in the supernatant liquid which has been decanted.

Fine particle, or particles that settle slowly, are often separated from a liquid by filtration. Support a funnel on a small ring on the ring stand as shown on Figure 1.3. If the ring is too large place a clay triangle on top of the ring to support the funnel Use a beaker to collect the filtrate. Adjust the funnel so that the stem of the funnel just touches the inside wall of the beaker. This will speed up the filtration process by decreasing the dropping, hence increases the continuous flow through capillary action due to the intermolecular force, hydrogen bonding.

Fold a circular piece of filter paper along its diameter, and then fold it again to form a quadrant. See Figure 1.4. Separate the folds of the filter, with three thicknesses on one side and one on the other; then place it into the funnel. The funnel should be wet before the paper is added. Use your plastic wash bottle to do this. Then wet the filter paper with a little water and press the edges firmly against the sides of the funnel so no air can get between the funnel and the filter paper while the liquid is being filtered.

EXCEPTION: A filter should not be wet with water when the liquid to be filtered does not mix with water. WHY?