CHEMISTRYLABORATORY PROCEDURES

INTRODUCTION: The best way to become familiar with chemical apparatus is to actually handle the pieces yourself in the laboratory. This activity is divided into several parts in which you will learn how to adjust the Bunsen burner, use an electronic balance, handle solids, measure liquids, filter a mixture, and measure temperature and perform heat calculations. Note all safety precautions that should be observed in each part and also pay attention to disposal and clean-up instructions.

SAFETY: Take the necessary safety precautions stated at the beginning of each part of this activity. Wear safety goggles and gloves where specified.

GOALS: As you perform these activities, you will:

  1. become familiar with common chemistry laboratory equipment
  2. follow directions to reach desired outcomes
  3. learn the locations of lab equipment and commonly used apparatus
  4. practice various laboratory manipulations common to many of the experiments you will perform later

Report

You will set up your lab notebook to record the results of the following procedures. Be sure to include a title, purpose, and headings for each of the sections which follow. Within each section, record all safety considerations and write out all questions and your answers. If necessary, design data and calculations tables for recording measured data. Show an example of each calculation which is performed.

PART 1, THE BUNSEN BURNER

Apparatus

Ceramic squareburner and tubingforceps or tongs

Evaporating dishsparker

Materials

Copper wire/wire loopcandlematches

Safety

  1. Wear safety goggles
  2. confine long hair and loose clothing

Procedures

As you perform the following steps, record your observations in your lab notebook and answer any questions which follow.

  1. The burner is used as a source of heat in the lab. Although the details of construction may vary among burners, each has a gas inlet located in the base, a vertical tube in which gas is mixed with air that has adjustable openings at the bottom of the barrel, and an inlet valve which offers some control over the flow of gas into the burner.
  1. Before lighting the burner, CLOSE the air vents at the base of the barrel and turn the gas full on. Hold the sparker about 3 cm above the top of the barrel and allow the gas a few seconds to flow through the barrel. Proceed to light the burner and then OPEN the air vents to provide the most efficient flame. If using matches to light the burner, FIRST strike the match and then turn on the gas and ignite the flame. Dispose of matches in the combustibles container.
  1. Experiment by completely closing the holes or air vents at the base of the burner.

QUESTION 1: WHAT IS THE RESULT OF CLOSING THE HOLES AT THE BOTTOM OF THE BURNER? Why do you think that happened?

  1. Using crucible tongs, grasp an evaporating dish carefully and pass it through the tip of the burner flame with the air vents open for about 1 minute. Examine the bottom of the dish. Place the dish on a ceramic square and light a candle. Now pass the dish through the flame of the candle for about 1 minute.

QUESTION 2: COMPARE THE RESULTS OF HEATING THE DISH IN THE BURNER FLAME VERSUS THE CANDLE. SUGGEST A POSSIBLE EXPLANATION FOR WHAT YOU OBSERVED.

INFORMATION: THE FLAME FROM THE CANDLE IS CONSIDERED TO BE “LUMINOUS” AND THAT OF THE BURNER “NONLUMINOUS”.

  1. Using forceps or crucible tongs, hold a piece of copper wire in the flame just above the opening of the barrel. Lift the wire slowly up through the middle of the flame. Continue to move the wire down to base of the flame and back up through the flame several times.

QUESTION 3: WHAT DID YOU OBSERVE? WHERE IS THE HOTTEST PART OF THE FLAME? How do you know it was the hottest?

  1. At the end of this section, all of the equipment that you store in your lab bin should be cool, clean and dry. Check to see that the gas valve is off. Dispose of oxidized copper wire in the trash.

PART 2, MEASURING LIQUIDS

Apparatus

Graduated cylinders, 10mL and 50mL or 100mL

Graduated pipet, 5mL, 10mL and pipet filler

Beaker, 100mL, 400mL

Erlenmeyer flask, 125mL

Materials

Tap water

Safety

  1. Wear safety goggles as others in the lab may be working on Part 1.

Procedures

As you perform the following steps, record your observations in your lab notebook and answer any questions which follow.

  1. Examine each of the measuring devices specified above. Determine the maximum readability of each device and record as 0.XX mL. Also determine if the device is a TC (to contain) or TD (to deliver) instrument if possible.

ASSIGNMENT: CREATE A TABLE IN THIS SECTION OF YOUR LAB NOTEBOOK TO ORGANIZE EACH DEVICE AND IT’S READABILITY AND TD AND/OR TC STATUS.

  1. Take the graduated pipet and the filler bulb. Attach the bulb to the top of the pipet by sliding the opening of the bulb over the top of the pipet. Do not push the bulb more than about 1 cm over the pipet.
  1. To use the pipet, you must squeeze the “A” valve before placing the tip of the pipet into the liquid to be measured. Next, lower the tip of the pipet into the liquid and squeeze the “S” valve to draw liquid into the pipet to a point just above the zero mark. DO NOT SIPHON LIQUID INTO THE BULB!
  1. To adjust the volume of liquid in the pipet to the zero mark, use the “E” valve and drain the excess liquid into the sink.
  1. To drain the measured liquid from the pipet, use the “E” valve and allow the pipet to gravity drain. To drain the last drop from the pipet, squeeze the small “drain” valve of the pipet bulb.
  1. Using the method described above, use the pipet to measure and drain precisely 5.00 mL of tap water into a 10 mL graduated cylinder.

QUESTION 4: READ AND RECORD THE VOLUME OF WATER IN THE GRADUATED CYLINDER. IS THE VOLUME EXACTLY 5 ML? WHY OR WHY NOT?

  1. Follow any additional clean-up instructions given by your instructor. Wipe off your lab table with damp towels and replace equipment if instructed. Do not leave the lab without permission.

PART 3, MEASURING MASS

Apparatus

Electronic Balanceplastic/foil massing dishes

spatula

Materials

Sodium chloride, NaCldistilled water

Safety

Do not touch chemicals even if they are apparently harmless. Always wear goggles. Wear gloves and aprons if specified. Do not return unused chemical reagents to original storage bottles unless told to do so.

Use extreme care when handling the balance. They are delicate instruments and are costly. If you have a problem with the function of your balance, let your instructor know.

Procedures

  1. Turn on your balance and make sure that the mode selected is in grams, as indicated by the arrow “” next to the “g” abbreviation. If the balance does not stabilize at 0.00 grams, press the “TARE” button and wait for the screen to display 0.00.
  1. As soon as the “” appears on the screen, you should be ready to use the balance as the 0.00 mass may change with vibration, wind currents, etc. If the 0.00 display does change, simply ready your materials and reset the “TARE” button.
  1. Use the directions above to obtain 1.95-2.05 grams of NaCl in a plastic massing dish. Use the “TARE” function to zero-out the mass of the dish once it is established. Slowly add NaCl until the desired mass displays on the screen.
  1. Save the NaCl as it will be used in Part 4. Clean up any spilled NaCl by wiping with a damp towel into the sink. Carefully clean the balance, do not press directly on the balance pan.

LABORATORY NOTEBOOK: RECORD THE MASS OF NaCl MEASURED.

PART 4, SEPARATORY METHODS; FILTRATION AND EVAPORATION

Apparatus

Ring standiron ringfilter paper

Stirring rod, glass or plasticwire gauzeevaporating dish

Sparkerwash bottle (dH2O)burner

2 beakers, 50 mL -100MlfunnelTripod stand

Materials

Sodium chloride from Part 3Sample of FeO

Sand

Safety

  1. Wear safety goggles
  2. Confine long hair and loose clothing

Procedures

  1. Sometimes liquids contain particles of insoluble solids, present either as impurities or as precipitates formed by the reaction of soluble compounds. If the particles are denser than water, they soon sink to the bottom. Most of the clear supernatant liquid may be poured off without disturbing the precipitate. Such a method is known as decantation.
  1. Obtain 1.95-2.05 grams of fine sand using electronic balance. Mix this sand with 40 mL of distilled water in a 50 or 100 mL beaker. Stir for 30 seconds. Allow the sand to settle to the bottom of the beaker and then decant the water into another 50 mL beaker.

QUESTION 5: HOW WELL DID YOU SEPARATE THE SAND FROM THE WATER? DID ANY SAND CARRY OVER INTO THE SECOND BEAKER?

  1. Dispose of the water and sand in the waste container provided. Dissolve the NaCl measured in Part 3 into about 20 mL of water in a 50 mL beaker. Stir in approximately a pea sized mound of FeO. THERE IS NO NEED TO WEIGH FeO JUST ADD APPROXIMATELY THE SAME AMOUNT AS THE NaCl.
  1. Support a funnel on a small ring attached to the ring stand or use a pipestem triangle to support the funnel. Place a beaker beneath the funnel to collect the filtrate. Fold a circular piece of filter paper as shown in the diagram below in half and then in fourths. Separate one edge of the folded paper to create a cone. Wet the funnel and place the filter cone into the funnel. Further wet the filter cone so it stays in the funnel.

QUESTION 6: WHY SHOULD THE FILTER CONE BE WET BEFORE FILTERING THE MIXTURE? Does it change anything in the mixture? If so, What?

  1. Again stir the mixture and then slowly pour into the wet filter cone which is supported by the funnel. Do not overfill the funnel. Filter at least half of the mixture.

QUESTION 7: WHAT DO YOU OBSERVE? WHAT PROPERTY OF IONIC SALT ALLOWS IT TO BE SEPARATED BY THE WATER?

  1. Take about 5 mL of the filtrate and place it in an evaporating dish. The evaporating dish may be supported on a wire gauze placed on a tripod stand or an iron ring attached to the ring stand. Gently heat the filtrate to complete dryness. If while heating the mixture begins to spatter, carefully move the burner from beneath the dish and allow the dish to cool slightly, then reheat.

QUESTION 8: WHAT DO YOU OBSERVE? WHAT PROPERTY OF THE WATER ALLOWS IT TO BE SEPARATED FROM THE NaCl BY HEATING?

  1. Carefully remove the evaporating dish with crucible tongs and rinse clean. Make sure that all equipment you store in the lab bin is completely clean, cool, dry, and arranged appropriately. Check to see that the gas valve is off.
  1. Wipe your lab table with a damp paper towel and replace equipment if directed to do so. Do not leave the lab without permission from your teacher.

PART 5, MEASURING TEMPERATURE AND CALCULATING HEAT CHANGES

Apparatus

Calorimeter(coffee cups with lid)buret clamp

Wire gauzegraduated cylinder, 50 mL

Burner and tubingbeaker, 600 mL

Celsius thermometersparker

Beaker tongsring stand or tripod stand

Iron ring

Materials

Tap water

Safety

  1. Be sure to confine loose clothing and tie back long hair.
  2. Use beaker tongs to handle the beaker of heated water.

INFORMATION: A thermometer is used to measure temperature and temperature changes. Examine your thermometer and the temperature range for the Celsius scale.

QUESTION 9: What is the readability of your thermometer?

Examine the calorimeter cup. A calorimeter is an apparatus used in measurements involving heat and heat transfer. For approximated measurements, the simple coffee-cup calorimeter may be used.

LABORATORY NOTEBOOK: Create a data table in your lab notebook to record the following measurements for 2 trials;

  1. volume of cold water in cup
  2. temperature of cold water in cup
  3. volume of heated water in beaker
  4. temperature of heated water in beaker
  5. final temperature of water mixture in cup

Also create a calculations table to record the result of the following calculations. (Show all work for BOTH trials performed.

  1. temperature change of cold water
  2. temperature change of hot water
  3. heat gained by cold water
  4. heat lost by hot water

Procedures

  1. Obtain two Styrofoam cups and a lid to function as the calorimeter. You will need 2 different thermometers, one to record the temperature of the heated water and one for monitoring the temperature within the calorimeter.
  1. Measure 40.0 mL of tap water in a graduated cylinder and pour it into your calorimeter.
  1. Measure 40.0 mL of tap water in a graduated cylinder and pour it into a 50 or 100 mL beaker. Set the beaker on a wire gauze over the tripod stand or on an iron ring with a thermometer immersed in the water. Support the thermometer in a double-buret clamp attached to a ring stand.
  1. Light the burner and monitor the temperature of the heated water. Warm the water to approximately 60C and turn off the burner.
  1. Allow the temperature of the heated water to equilibrate and then record the temperature of the warm water in your data table. Working quickly but carefully and using a different thermometer, measure the temperature of the cold water in the calorimeter and record.
  1. Using beaker tongs, immediately transfer the hot water into the calorimeter cup. Replace the lid, insert the thermometer, and stir or swirl the cup gently and continuously until a fixed temperature is reached. Record this final temperature of the mixture in your data table.
  1. Dump the water from the cup and repeat the experiment for an additional trial. When finished, make sure all stored equipment is cool, clean, and dry. Make sure gas valves are off. Wipe you table with damp towels. Do not leave the lab without permission. Wash your hands.

Calculations

  1. Show all work in your lab notebook. Label calculations clearly and record the result of calculations in your table. Calculate the temperature change, T, of the cold water in each trial.

Final temperature  initial temperature = T

  1. Calculate the T of the hot water;

Initial temperature  final temperature = T

  1. The quantity of heat, Q , that is gained and lost may be calculated from the following equation:

Q (joules) = temperature change (T) x mass (g) x

Using this equation, calculate Q for the heat gained by the 40 mL of cold water in each lab trial. Assume that 40 mL of water has a mass of 40 grams. Record the results in your calculations table.

  1. Using the equation above, calculate Q for the heat lost by the 40 mL of hot water. Again assume that 40 mL of water has a mass of 40 grams. Record the results in your calculations table.

QUESTION 10: HOW DOES HEAT LOST AND GAINED COMPARE WITHIN EACH TRIAL? CALCULATE THE DIFFERENCE IN Q GAINED AND LOST IN TRIAL 1. DO THE SAME FOR TRIAL 2. WHY MIGHT HEAT GAIN AND LOST NOT BE THE SAME?

RELATIVE ERROR OR PRECISION CALCULATION: FREQUENTLY IN SCIENCE AN ABSOLUTE OR TRUE VALUE IS NOT KNOWN. THE ACCURACY OF YOUR MEASUREMENTS AND CALCULATIONS CANNOT BE CALCULATED WITHOUT A TRUE VALUE BEING KNOWN. PRECISION IS A MEASURE OF HOW REPRODUCIBLE EXPERIMENTAL RESULTS ARE. PRECISION CAN BE CALCULATED IF WE KNOW THE AVERAGE Q GAINED AND LOST. TO IMPROVE RELIABILITY, WE WILL USE THE CLASS AVERAGE VALUES TO DETERMINE PRECISION. BE PREPARED TO SHARE YOUR Q-GAINED AND Q-LOST VALUES.

CALCULATION: DETERMINE THE PRECISION IN YOUR VALUES BY CALCULATING THE %DEVIATION AS SHOWN BELOW.

Percent deviation = x 100

CLASS DATA FOR PART 5: CALORIMETRY

Heat Gain (J) / Heat loss (J)
Group / T-1 / T-2 / T-1 / T-2
1 / 3.50x10^3 / 3490 / 3690 / 4020
2 / 1790 / 3590 / 4920 / 4.10x10^3
3 / 3.44x10^3 / 3.49x10^3 / 3.98x10^3 / 3.98x10^3
4 / 3680 / 3490 / 3630 / 3290
5 / 3370 / 3540 / 3810 / 4460
6 / 3880 / 3410 / 3950 / 4.40x10^3
7 / 3390 / 3330 / 4030 / 4360
8 / 3660 / 3680 / 4210 / 4010
9 / 3540 / 3730 / 4140 / 4130
10 / 3580 / 3830 / 3830 / 3980
11 / 4.60x10^3 / 3.74x10^3 / 3.0x10^3 / 3.88x10^3
12
mean / 3530 / 3990

IN YOUR LAB NOTEBOOK:

Mean heat gain =3530 / Mean heat loss =3990
T-1 deviation from mean
T-2 deviation from mean
Avg. deviation from mean
% deviation

CLASS DATA FOR PART 5: CALORIMETRY

Heat Gain (J) / Heat loss (J)
Group / T-1 / T-2 / T-1 / T-2
1 / 3260 / 3430 / 3090 / 3750
2 / 3090 / 3260 / 3930 / 3850
3 / 3640 / 3340 / 3940 / 4340
4 / 3430 / 3930 / 2600 / 2590
5 / 2510 / 3430 / 5180 / 4290
6 / 3640 / 3510 / 4050 / 4210
7 / 3450 / 3730 / 3580 / 4170
8 / 4010 / 3930 / 2840 / 4010
9 / 3180 / 3430 / 3850 / 4180
10 / 3590 / 3510 / 4.10x10^3 / 4.10x10^3
11 / 3440 / 3590 / 4510 / 3860
12
mean / 3470 / 3680

IN YOUR LAB NOTEBOOK:

Mean heat gain =3470 / Mean heat loss =3680
T-1 deviation from mean
T-2 deviation from mean
Avg. deviation from mean
% deviation