Category Archives: Chemistry Laboratory

Lab 11: Photochemistry

For this lab, we are going to perform the photochemical reaction of iodine and oxalate. We will be running the experiment until two hours after we set it up, so we will likely go 15 or so minutes over our usual lab time.

We will also do other labs and activities as demonstrations to fill in while we wait between observations of the experiment. You won’t be asked to write those up in your lab notebook.

Reading:  The Home Scientist Lab Manual Topic XI. Photochemistry Session XI-1: Photochemical Reaction of Iodine and Oxalate pp. 182-186. This will be the lab we are writing up. 

Two demonstrations we will be doing from the Home Scientist:  Topic III Session 1 and 2, read pp. 70-74. You do not need to write these up.

Experimental Title: Lab 11:  Photochemical Reaction of Iodine and Oxalate

Date of laboratory:  August 12, 2014

Purpose: The purpose of this laboratory is to observe photochemical initiation of the oxidation of iodine to iodide by oxalate, as well as to determine the effect of wavelength on photochemical initiation of a reaction.

Introduction:

Read the background to the experiment on page 183-top 0f page 184.

Write the equations for the reactions in your notebooks. Also, summarize what the color changes or lack of color changes mean about how far the reaction has progressed.

Special safety concerns for Lab 11:

  • This week the most hazardous material is the 6M Ammonia.Please use gloves and goggles at all times when handling this material. It is corrosive and the vapor can be irritating. (MSDS for 6M Ammonia)
  • You may remember from the oscillating reaction that iodine can stain. Sodium thiosulfate makes it colorless again.
  • If glass test tube breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands very carefully when you are finished with this lab.

Materials:  See list page 183.

light-bulb-turn

(Public domain image by George Hodan)

 

Procedures:

Write down the Procedure on pages 184-186 the lab manual. Be sure to leave room for the data table to record your results.

Conclusions:

Once you have completed the experiment and cleaned up, sit down and write a sentence or two to explain the results. It is always a good idea to do this part while the experiment is fresh in your mind.

Discussion:

Record any thoughts you have about the experiments, including:

  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Whether the goals were met
  • Suggestions for other experiments
  • The answers to the review questions he provides on page 186.

Please leave a comment or send an e-mail if you have any questions before our meeting.

Lab 10: Double Displacement Reactions

For today’s lab, we are going to build on some of the information about classifying chemical reactions we learned last week.

Reading:  The Home Scientist Lab Manual Topic III-4. Observe Double Replacement Reactions p.77-82,

Experimental Title: Lab 10:  Double Displacement Reactions

Date of laboratory:  August 5, 2014

Purpose: The purpose of this laboratory is to observe a series of double displacement reactions.

Introduction:

Read the background to the experiment on page 77-78.

It is a bit confusing, but chemists use the terms “double-replacement” and “double displacement” interchangeably, and this type of reaction may also be called a “metathesis” reaction. Extra credit to anyone who can find out which term is better to use or if one term is “displacing” the other. For our class, I will accept all these terms, but I will follow the textbook and call it double displacement in my own writing.

A double displacement reaction involves two compounds switching ions. If A and B are cations and X and Y are anions, then the reaction is AX + BY -> AY + BX.

In this lab session, we will test dilute solutions of the following eight cations:
□ Barium(II) or Ba2+ (from barium nitrate solution)
□ Calcium(II) or Ca2+ (from calcium nitrate solution)
□ Copper(II) or Cu2+ (from copper(II) sulfate solution)
□ Hydrogen or H+ (from hydrochloric acid solution)
□ Iron(II) or Fe2+ (from iron(II) sulfate solution)
□ Iron(III) or Fe3+ (from iron(III) chloride solution)
□ Lead(II) or Pb2+ (from lead(II) acetate solution)
□ Magnesium or Mg2+ (from magnesium sulfate solution)
against the following twelve anions:
□ Bromide or Br- (from potassium bromide solution)
□ Carbonate or CO32- (from sodium carbonate solution)
□ Chloride or Cl- (from hydrochloric acid solution)
□ Dichromate or Cr2O72- (from potassium dichromate solution)
□ Ferricyanide or [Fe(CN)6]3- (from potassium ferricyanide solution)
□ Ferrocyanide or [Fe(CN)6]4- (from sodium ferrocyanide solution)
□ Hydroxide or OH- (from sodium hydroxide solution)
□ Iodide or I- (from potassium iodide solution)
□ Oxalate or C2O42- (from oxalic acid solution)
□ Phosphate or PO43- (from phosphoric acid solution)
□ Sulfate or SO42- (from magnesium sulfate solution)
□ Sulfide or S2- (from sodium sulfide solution)
to determine if a reaction occurs.

If you have time, do some research and see if you can make some predictions as to what might happen in each of the pairings.

Special safety concerns for Lab 10:

This week we have to take lab safety very seriously. We are only doing this lab because you have shown you can be responsible up to now. Keep up the good work.

  • Important:  Be sure to wear gloves and goggles for the entire lab this week. Also, please wear long pants and closed-toe shoes. No exceptions this week!
  • We will be doing the experiments in trays this week. Keep all the chemicals in the trays, please.
  • The most dangerous chemicals are :  6M hydrochloric acid and the 6M sodium hydroxide. Those are strong concentrations. Barium, lead and dichromate can also be toxic. Use extra caution with those chemicals.
  • If an acid spills, especially the 6M hydrochloric acid, cover the area of the spill with baking soda immediately! If it on you, go wash in the sink. Notify your instructor.
  • If a base spills, especially the 6.0 M Sodium hydroxide, please cover it immediately with acetic acid (vinegar). If it on you, go wash in the sink. Notify your instructor.
  • If glass breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands very carefully when you are finished with this lab.

Materials:

See the list page 77.

Procedures:

Write down the Procedure on pages 78-81 the lab manual. Be sure to leave room for the data table to record your results. It might be useful to underline, star, or otherwise note the 6M hydrochloric acid, 6M sodium hydroxide, barium, lead and dichromate whenever you work with them so you know those are chemicals to use with extra caution.

Edit:

24-Well Reaction Plate:

24-well-reaction-plate-template

Conclusions:

Once you have completed the experiment and cleaned up, sit down and write a sentence or two to explain the results. It is always a good idea to do this part while the experiment is fresh in your mind.

Discussion:

Record any thoughts you have about the experiments, including:

  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Whether the goals were met
  • Suggestions for other experiments
  • The answers to the review questions he provides on page 82.

Please leave a comment or send an e-mail if you have any questions before our meeting.

Lab 9: Topic III, Classifying Chemical Reactions

Note:  After trying out the experiments for this lab, we decided to do some modifications. We will still do Home Scientist session III-3 today, but we will do Home Scientist sessions III-1 and III-2 on August 12 because they both work better with butane torch. Today we will do a precipitation/double-displacement reaction, as well as a gas-evolving reaction instead. We will also re-visit salting out from last week.

Reading:  The Home Scientist Lab Manual Topic III. Classifying Chemical Reactions. Introduction pp. 66-69. We will be doing Session III-3. Observe a single replacement reaction pp. 75- 76.

Experimental Title: Lab 9:  Classifying Chemical Reactions

Date of laboratory:  July 29, 2014

Purpose: The purpose of this lab is to explore various aspects of classifying chemical reactions. We will carry out a single replacement reaction, as well as a precipitation/double-displacement reaction and a gas-evolving reaction.

Introduction:

Read the introduction to this section in the lab manual, pp. 66-69, as well as the background to the experiment on page 75.

Chemical reactions may be classified in various ways.

One way to classify chemical reactions is by what type of chemistry is happening.

  • Precipitation reactions
  • Gas Evolution
  • Acid-base or Neutralization
  • Oxidation-Reduction 

 A second way to classify reactions is to look at what the atoms are doing.

  • Synthesis or combination
  • Decomposition
  • Displacement
  • Double-displacement

Equation for single-displacement reaction (part 1):

Fe (s) + CuSO4 (aq) –> FeSO4 (aq) + Cu (s)
Fe (s) + Cu2+ (aq) + SO42- (aq) –> Fe2+ (aq) + SO42- (aq) + Cu (s)

Equation for precipitation/double-displacement reaction (part 2):

MgSO4(aq) + Na2CO3(aq) → MgCO3(s) + Na2SO4(aq)

Equation for gas-evolving reaction (part 3):

NaHCO3(aq) + KHC4H4O6(aq) → KNaC4H4O6(aq) + H2O + CO2(g)

(This is actually a 2 step reaction.)

Special safety concerns for Lab 9:

  • Be sure to wear gloves and goggles this week.
  • Alcohol is flammable, so please keep it away from any sources of heat or sparks.
  • If anything spills, please clean it up immediately with a paper towel and let your instructor know.
  • If glass breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands when you are finished with this lab.

Materials:

Part 1, see list page 75. Add clock/watch and cotton swabs (to clean wells).

Part 2: 

  • Magnesium sulfate (Epsom salt)
  • Sodium carbonate (made by heating baking soda)
  • Water
  • 2 clear plastic cups
  • 2 small paper cups for weighing
  • Scale
  • Stirring rods
  • Measuring spoons
  • Graduated cylinders

Part 3:

  • Sodium bicarbonate (unheated baking soda)
  • Potassium bitartrate (Cream of tartar)
  • Water
  • 2 small paper cups for weighing
  • Beaker or clear plastic cup
  • Plastic wrap – piece to cover beaker or plastic cup

Procedures:

Part 1. Session III-3 Single Replacement Reaction

Go ahead and write down the Procedure on pages 75-76 the lab manual with these adjustments:

Step 2. Add:  Take the temperature of the copper (II) sulfate solution and record it.

Step 4. It turns out to be very important to use exactly the same amount in each well of the reaction plate, or you won’t be able to see the color differences (more material means darker color). Also, try not to pick up and transfer any bits of iron with the pipette.

Step 5. Add:  Check the temperature of the copper (II) sulfate solution again. Any changes?

Be sure to leave room in your notebook to record the temperature, amounts of materials used, observations, etc.

Part 2:  Double-displacement/precipitation reaction

Obtain the materials listed above

1. Pour 100 mL of water in one clear plastic cup. Weigh 10 g (about 1 tablespoon) of magnesium sulfate into a paper cup (remember to tare). Add to the water and stir until the solution is clear.

2. Pour 50 mL of water in another clear plastic cup. Weigh 5 g (about 1 teaspoon) of sodium carbonate into a paper cup. Add to the 50 mL of water and stir until the solution is clear.

3. Once both solutions are prepared and clear, pour the sodium carbonate solution into the magnesium sulfate solution.

Record your observations:

Part 3:  Gas evolving reaction

1. Weigh 6 g of sodium bicarbonate (baking soda) into a small paper cup, using the scale.

2. Weigh 4.5 g of potassium bitartrate (Cream of tartar) into a paper cup, using the scale.

3. Add 100 mL water to a clean beaker or clear plastic cup. Add the two powders you weighed out to the water and then cover the cup or beaker quickly with a piece of plastic wrap.

Record your observations:

Conclusions:

Once you have completed all three parts, sit down and write a sentence or two to explain the results.

Discussion:

Record any thoughts you have about the experiments, including:

  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Whether the goals were met
  • Suggestions for other experiments
  • The answers to the review questions he provides on page 76.

Please leave a comment or send an e-mail if you have any questions before our meeting.

Lab 8: From Topic I, Recrystallization and Salting Out

From this week on, we are going to start working through the Home Scientist Lab Manual. Did you download the Home Scientist CK01A Standard/Honors Home School Chemistry Laboratory Manual already? You’ll need to use it for the rest of the course.

Important Note:  We will not be working through the manual in order, but instead we will be performing labs as they align to the concepts presented in the textbook. Therefore, you will have to pay close attention to which labs are assigned, and how they are being modified.

Reading:  Topic I. Separating Mixtures. We will be doing Session I-1. Recrystallization  pp. 21-26 and Session I-4. Salting Out, pp. 39-41.

Experimental Title: Lab 8:  Investigating Solubility, Recrystallization and Salting Out

Date of laboratory:  July 22, 2014

Purpose: The purpose of this laboratory is to examine concepts relating to solubility. We will investigate how temperature affects solubility, how to isolate pure sodium bicarbonate via a recrystallization technique, and how to utilize differential solubility to separate water and isopropyl alcohol by a salting out procedure.

Introduction:

You may skip reading the introduction in the lab manual, pp.19-20 because it pertains more to separating mixtures than solubility, which is what we are interested in this week. Instead, use the background information from each lab session for your own lab notebook introduction. The background information can be found on pp. 21-24 and pp. 39-40. You don’t need to write down everything word-for-word, but you might want to jot down important concepts. You can also supplement information from the text/lesson if you find it useful.

The solute is the smallest part of a solution, or the substance being dissolved.

The solvent is the larger part, or the part doing the dissolving.

A solution is a solute dissolved in a solvent.

Miscible means two substances that can mix, and particularly that they can form solutions in any proportion. That means that both substances can be present as the smaller portion or as the larger portion.

Recrystallization involves making a supersaturated solution and then adding more solute. This causes the solute to fall out of solution in the form of pure crystals.

Special safety concerns for Lab 8:

Please start by carefully reading the Lab Safety section, pages 10-13.

  • If anything spills, please clean it up immediately with a paper towel and let your instructor know.
  • Alcohol is flammable, so please keep it away from any sources of heat or sparks.
  • If glass breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands when you are finished with this lab.
  • We will discuss whether to actually do the tasting he suggests for session I-1.

Materials: See lists page 21 and 39.

Procedures:

Session I-1 Recrystallization

Go ahead and write down the Procedure on pages 24-25 the lab manual with these adjustments:

For each measurement, use the quantity he lists (for example one teaspoon),  and then weigh it on the scale to convert to grams. Adjust your methods accordingly. (He assumes that the people using the kit might not have scales).

Edit:  Further details about changes made 7/21/2014. Please follow the procedure in the manual with the following changes:

Step 2. Weigh a small paper cup on the scale. Record the weight in grams. Add one teaspoon of table salt and 3 heaping Tablespoons of baking soda to the cup. Mix thoroughly and weigh again. Record the weight. Subtract the weight of the cup and record the weight of the mixture in grams.

Step 3. Use 100 mL of cold tap water.

Step 4. Once you have added the mixture until just a few grains remain undissolved, weigh the paper cup with mixture again so you know exactly how many grams you used. You don’t need to keep track of the teaspoons.

Step 5. As the solution is heating, add the mixture again until just a few grains remain undissolved. Take the temperature and weigh the cup to calculate how much mixture you used. This will give you an additional data point between room temperature and boiling.

Step 6. Once again, at the end weigh the cup plus mixture when you have added the necessary amount, and record the final weight. Subtract the weight of the cup you recorded earlier for the weight of the mixture used. Record the final mass in grams.

Note:  Don’t leave the stirring rod in the beaker between stirs. It will get very hot.

During Step 7 we will use the time we are waiting for the solution to cool to set up the salting out experiment (Session I-4) and to graph the results you obtained.

Step 14. We will replace the hydrochloric acid with acetic acid, which also bubbles when baking soda is present.

Be sure to leave room in your notebook to record the temperature, amounts of materials used, observations, etc.

Session I-4:  Salting Out

Again, write out his instructions on page 40. We will be using food coloring, because otherwise the two layers might be hard to tell apart.

Conclusions:

Once you have completed both sessions, sit down and write a sentence or two to explain the results.

Discussion:

Record any thoughts you have about the experiments, including:

  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Whether the goals were met
  • Suggestions for other experiments
  • The answers to the review questions he provides.

If there is time, we’ll go over the review questions together at the end of lab.

Please leave a comment or send an e-mail if you have any questions before our meeting.

Lab 7: Finding Moles and Molecules

In this lab we are going to get more comfortable using moles by the determining the mass of some everyday substances, and then use this mass to calculate the numbers of moles and molecules/atoms the substance contains. We are also going to investigate electrolysis, a process that can be used to experimentally determine the value for mole (Avogadro’s number), as well as to demonstrate the molecular formula of water.

Experimental Title: Lab 7:  Investigating Moles and Numbers of Atoms/Molecules in Common Substances

Date of laboratory:  July 15, 2014

Purpose: The purpose of this laboratory is to determine the mass in grams, number of moles, and the number of molecules/atoms in small amounts of everyday substances. It is also to investigate electrolysis of water.

Introduction:

It is possible to relate to the mass of an object or substance, because it is tangible. You can feel how much mass a rock or a carrot has. Chemists often must have an idea how many atoms or molecules a substance contains, however, which is a number that is much more difficult to conceptualize.

The mole is used in chemistry to help make that transition. One mole of anything is 6.022 x 1023 items of that substance. It allows the chemist to use atomic masses from standard periodic tables (the mass of a single atom of an element is expressed in atomic mass units or amu, where 1 amu is 1/12 the mass of an atom of C12), simply by changing the unit from atomic mass units to grams. For example, one atom of hydrogen has an average mass of 1.008 amu, whereas one mole of hydrogen atoms has an average mass of 1.008 g. Wasn’t that easy?

Mole or Avogadro’s number = 6.022 x 1023

How did chemists arrive at Avogadro’s number? One way to do so experimentally is to examine the electrolysis of water. This video gives a quick explanation of how electrolysis can be used to supply data for the calculations:

The reaction for the electrolysis of water is
2H20 → O2 + 2H2

 

Special safety concerns for Lab 7:

  • If anything spills, please clean it up immediately with a paper towel and let your instructor know.
  • If glass breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands when you are finished with this lab
  • Avoid touching the battery with wet hands and don’t touch both terminals at once to avoid shocks.

Materials:

  • Empty aluminum can
  • Aluminum foil
  • Copper sample
  • Baking soda box with label
  • Magnesium sulfate
  • Sodium chloride
  • Sidewalk chalk
  • 9 Volt battery
  • Plastic cup
  • 2 metal tacks
  • 2 test tubes
  • Sink or tub to fill test tubes in
  • Rubber bands
  • Water
  • Graduated cylinders
  • Table top scales
  • Transfer pipette
  • Sharpie pen
  • Calculator
  • Periodical Table of the Elements with Atomic Mass listed

Procedures:

Note:  You can do the parts in any order, so go ahead to another part and come back to finish if you need to do so. No need to wait for materials.

Part 1. Moles, mass and number of Atoms: elements

Element:  Aluminum

1. Find the mass of one mole of aluminum using the value of atomic mass listed on the periodic table.

Value:

 2. Obtain an empty aluminum can. Weigh the can on a balance and record its mass in grams.

Mass:

3. Calculate how many moles of aluminum are in one aluminum can.

Number of moles:

4. Create a piece of aluminum foil that weighs as much a one mole of aluminum, using the balance. Save this sample to compare with other examples of one mole of a substance.

Element:  Copper

1. Find the mass of one mole of copper using the value of atomic mass listed on the periodic table.

Value:

2. Obtain a sample piece of copper. Weigh on a balance and record its mass in grams.

Mass:

3. Calculate how many moles of copper are in the sample.

Number of moles:

4. Using the number of moles, calculate the number of copper atoms found in the sample piece.

Number of atoms:

Element:  Sodium

1. Find the mass of one mole of sodium using the value of atomic mass listed on the periodic table.

Value:

2. Obtain a baking soda box. Looking at the label, how many mg of sodium are in one serving of baking soda?

Mass:

3. Calculate how many moles of sodium are in a single serving of baking soda.

Number of moles:

4. Using the number of moles, calculate the number of sodium atoms found in one serving of baking soda.

Number of atoms:

5. If a recipe for biscuits calls for 3 teaspoons of baking soda, how many moles of sodium are in the biscuits?

 

Part 2. Moles, mass and number of Molecules: Compounds

Compound:  Water

1. Find the mass of one mole of water using the value of atomic masses listed on the periodic table.

Molar mass of water:

2. Tare a graduated cylinder. Add 10 mL of water and weigh.

Mass of 10 mL of water:

3. Calculate how many moles of water are in 10 mL.

Number of moles:

4. Using the number of moles, calculate the number of water molecules found in 10 mL.

Number of molecules:

5. Weigh out one mole of water using a graduated cylinder and a scale. Compare the relative size/volume to one mole of aluminum (foil). Save your sample in a cup or beaker to compare to other examples of one mole of a substance.

Compound:  Sodium chloride

1. Find the mass of one mole of sodium chloride using the value of atomic masses listed on the periodic table.

Molar mass of sodium chloride:

2. Obtain a sample of sodium chloride. Determine the mass of the sample in g using the scale.

Mass of sodium chloride sample:

3. Calculate how many moles of sodium chloride are in the sample.

Number of moles:

4. Using the number of moles, calculate the number of sodium chloride molecules found in the sample.

Number of molecules:

5.How many individual ions (both cations and anions) are in the sample?

6. Weigh out one mole of sodium chloride. Compare the relative size/volume to one mole of aluminum (foil) and one mole of water.

 

Compound: Sidewalk chalk

Determine how many moles of sidewalk chalk it takes to write your name on the sidewalk. Note: Sidewalk chalk is made out of calcium sulfate (CaSO4) rather than the calcium carbonate (CaCO3) used for chalkboard chalk.

1. Find the mass of one mole of calcium sulfate using the value of atomic masses listed on the periodic table.

2. Weigh a piece of sidewalk chalk.

Weight of chalk before writing your name:

3. Go outside and write your name on the sidewalk. Come back inside and weigh the chalk again.

Weight of chalk after writing your name:

Grams of sidewalk chalk required to write your name:

How many moles of calcium sulfate was needed to write your name?

test-tubes

Part 3. Electrolysis of Water

1. Obtain a plastic cup, 9 volt battery, 2 metal tacks, a Sharpie pen, 2 test tubes and some magnesium sulfate or Epsom salts. (Baking soda would also work.)

2. Press the 9 volt battery against the bottom of the cup and mark where the terminals touch.

3. Press the tacks through the bottom of the cup at those points, so the terminals of the battery can touch the flat tops of the tacks and the points are projecting into the cup.

4. Fill the cup about 3/4 full with water. Add a teaspoon of Epsom salts and stir.

5. Take the apparatus to the sink. Fill the sink with enough water to be able to submerge the test tubes. You will want to put your thumb over the filled test tube under water and then transfer the tube to the cup so the open end is submerged and no bubbles are trapped in the top. Hold the tube upright.

6. Repeat with the second test tube. Now position the two tubes so that one is over each thumbtack. Wrapping the testube with a rubber band wwill help keep them together and upright.

7. While one person holds the cup and tubes, lift it up so the second person can touch the battery to the two tacks.

Record your observations:

This video from ScienceFix shows the setup in the first part.

He shows it sitting by itself, but you will probably need to at least hold the test tubes upright.

Conclusions:

Once you have completed the parts, sit down and write a sentence or two to explain the results of each.

Discussion:

Record any thoughts you have about the experiments, including:

  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Suggestions for other experiments
  • What key concepts you learned about mass, moles, numbers of molecules and the electrolysis of water

Please leave a comment or send an e-mail if you have any questions before our meeting.

Lab 4: Heat Capacity

Today we are going to investigate energy flow and specific heat capacity using a coffee cup calorimeter.

Experimental Title: Lab 4:  Heat Capacity

Date of laboratory:  June 24, 2014

Purpose: The purpose of this laboratory is to investigate the flow of thermal energy between substances until they reach thermal equilibrium.

Introduction:

Thermal energy is transferred from an object or substance with higher thermal energy to one at a lower thermal energy, until the two reach thermal equilibrium. 

Chemists often use a calorimeter to study thermal energy transfer. A common set up is called a “coffee cup calorimeter.” It consists of an insulated Styrofoam cup and a thermometer. To improve sensitivity, sometimes two Styrofoam cups are used, one inside the other and a cardboard, plastic or cork lid is added with a hole for the thermometer. This provides further insulation and less loss of thermal energy to the surroundings.

How much the temperature of a given substance increases for a given amount of heat transferred varies from substance to substance. The heat capacity is how much heat (measured in joules) is needed to raise the temperature of a given amount of substance 1°C. The specific heat capacity assumes the amount of the substance is measured in grams.

Equation:  q = m x C x ∆T

  • where q = amount of heat absorbed (joules)
  • m = mass (in g)
  • C = specific heat capacity (j/g °C)
  • ∆T = change in temperature (°C)

The specific heat capacity (C) for water is 4.184 J/g °C  and for copper is 0.385J/g °C.

Special safety concerns for Lab 4:

  • Today we will be wearing eye protection.
  • If boiling water spills on you, run cold water from the sink onto the area immediately. Don’t think, just run to the sink.
  • If the glass thermometer breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands when you are finished with this lab.

Materials:

  • Eye protection
  • Stove
  • Oven mitts
  • Pan
  • Thermometer
  • Water
  • Ice
  • Styrofoam cups
  • Graduated cylinders
  • Table top scale
  • Strainer or colander
  • Pennies
  • Spoons
  • Clock
  • Calculator

Procedures:

Part 1:
1.    Pour 100 mL of water at room temperature into a large Styrofoam cup.  Insert the thermometer, taking care not to touch the walls of the cup. Determine the initial temperature of the water and note it in your notebook (see suggested data table below). Remove the thermometer from the cup.
2.    You will be adding 100 mL of boiling water to the cup. Using the initial temperature of the room temperature water, and assuming the temperature of boiling water to be 100°C, predict the final temperature of the mixture when the two samples are combined. Record your prediction in your notebook.
3.    Using a graduated cylinder, measure 100 mL of water. Pour the water into the pan provided and heat on the stove until it boils. Using oven mitts, carefully pour the 100 mL of boiling water into the Styrofoam cup with the room temperature water. If you want to stir the water, use a spoon and not a thermometer.
4. Take a temperature reading every minute until the mixed water reaches thermal equilibrium (when the temperature no longer changes, probably between four and six minutes). Record the final temperature in your notebook.

Part 2:
Repeat Part 1 using 75 mL room temperature water in step 1 and 225 mL of boiling water in step 3.

Part 3:
Repeat Part 1 using 225 mL of room temperature water in step 1 and using 75 mL of boiling water in step 3.

Part 4:
Repeat Part 1 using 100 mL of room temperature water for step 1 and 100 mL ice water for step 3.

Suggested Water Temperature Table (Parts 1-4)

heat-capacity-table-water

Part 5:
1.    Weigh 35 pennies using the scale. Record the mass. (It should be close to 100 g.)
2.    Measure out an equal mass of room temperature water (remember 1 mL water is approx. 1 g). Pour the water into a large Styrofoam cup, insert the thermometer and record the temperature. Remove the thermometer.
3.    Cover the pennies with water in a pot and heat the water to boiling.
4.    While the pennies are heating, predict the final temperature that will result when the hot pennies (assume 100°C) are mixed with an equal mass of water in the cup. Record this value in your notebook.
5.    Drain the pennies in a colander over the sink to remove as much water as possible. Pour the hot pennies into the Styrofoam cup. Measure the final temperature as before and record in your notebook.

Part 6:
1.    Dry the 35 pennies and weigh again.
2.    Measure out an equal mass of room temperature water. Pour the water into a large Styrofoam cup, insert the thermometer and record the temperature. Remove the thermometer.
3.    Cover the pennies with ice water.
4.    While the pennies are cooling, predict the final temperature that will result when the cold pennies (assume near 0° C) are mixed with an equal mass of water in the cup. Record this value in your notebook.
5.    Drain the pennies to separate them from the ice and water and pour them into the Styrofoam cup. Measure the final temperature and record in your notebook.

Water Plus Pennies Temperature (Parts 4 and 5)

heat-capacity-table-pennies

Calculations:

Now calculate the amount of heat (q) for water and pennies. We will work on this together in lab.

Conclusions:

Once you have completed the six parts, sit down and write a sentence or two to explain the results of each part.

Discussion:

Record any thoughts you have about the experiments, including:

  • Why did we perform the experiments in Styrofoam cups?
  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Suggestions for other experiments
  • What key concepts you learned about heat capacity

We’ll go over the key concepts together at the end of lab.

Please leave a comment or send an e-mail if you have any questions before our meeting.

Lab 3: Separation of Mixtures

In this lab we are going to investigate different ways to separate mixtures of substances by taking advantage of their physical properties. It will be inquiry-based, and you and your group will get to decide which techniques you want to use to separate a heterogeneous mixture of sand, poppy seeds, beans, salt and iron fillings.

Experimental Title: Lab 3 Separation of Mixtures

Date of laboratory:  June 17, 2014

Purpose: The purpose of this laboratory is to learn procedures and techniques used to separate mixtures of substances based on their physical properties.

Introduction:

A mixture is a combination of two or more substances in varying proportions. Scientists often need to separate mixtures into their components for analysis or to use in an experiment. It is possible to exploit differences in physical properties to separate substances from a mixture.

Special safety concerns for Lab 3:

  • If anything spills, please clean it up immediately with a paper towel and let your instructor know.
  • If glass breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands when you are finished with this lab

Materials:

    • A heterogeneous mixture of beans, sand, salt, poppy seeds, and iron fillings
    • Forceps
    • Magnet
    • Plastic bag with tie
    • Beakers
    • Water
    • Graduated cylinders
    • Filter paper
    • Transfer pipette
    • Soda bottle filter
    • Soda bottle distillation apparatus (soda bottle cut in half, with lid)
    • Ice
    • Newspapers
    • Aluminum foil
    • Containers to hold separated substances
    • Plastic spoons

Procedures:

For this laboratory you and your group will decide which of the following procedures you will use to separate the mixture you receive. Keep in mind that you may need to repeat some procedures at different stages of the process. Go ahead and write the procedures below in your notebook now and you can refer to them by number as you use them. For example, “We added 25 mL of water, and then used procedure 4 to filter the mixture.” Be sure to write down the actual steps you use on lab day as well.

Procedure 1. Sorting or Manual Separation

Substances may differ in this size, shape and color. If the differences are large enough, it may be reasonable to simply pick out one of the substances with a pair of forceps and place it in a separate container.

candy-pick-out

For example, it would be relatively easy to pick the white jellybeans out of this mixture.

Procedure 2. Use a magnet to remove certain metals

Some substances (certain metals) are attracted to magnets and others are not. You can use this difference in magnetic properties to separate some mixtures.

If the metal fragments are small, place the magnet in a plastic bag and tie it shut. 

magnet-sand-setup

The baggie covering will make the metal fragments easier to remove from the magnet.

magnet-sand-results

Drag the magnet over the mixture to attract magnetic metals. Brush the attracted metals off the plastic bag into a separate container.

Side note:  Have you ever tried this at the beach? Sand naturally contains iron fragments. In some places you might even be able to find small meteorites.

The following procedures require the addition of water to the mixture. Remember that if you add water, you might be dissolving some of the substances in the mixture. For example, salt or sugar dissolve into water making a solution.

Procedure 3. Decanting

It is possible to separate some substances based on differences in density. For example, oil floats on top of water. Add water, allow the substances to separate based on density, and then pour the upper layer with the less dense materials into a separate container.

If you have never done it, this video shows the standard way to decant in chemistry (direct link).

Procedure 4. Filtration

Filtration takes advantage of differences in particle size to separate mixtures. Generally filtration in chemistry involves special glassware, such as shown in figure 3.14 on page 65 in the textbook.

In this lab, we will use a large soda bottle cut in two, with the top inverted into the bottom.

soda-bottle-filter

Place the filter paper into the top of the soda bottle filter. Pour the liquid to be filtered through the filter. Larger particles will be trapped in the filter, and the liquid and smaller particles will pass through into the catchment container. Remove the filter and invert into a dish. Scrape off the solids with a spoon, if necessary.

Procedure 5. Evaporation

Both evaporation and its cousin, distillation, depend on differences in boiling points to separate materials. For example, with a solution of salt and water, the water has a lower boiling point. When heat is applied, the water boils away and the salt is left behind.

It is also possible to leave the solution in the sun for several days. The heat from the sun evaporates the water, again leaving the salt behind.

Evaporation involves applying energy to a solution in the form of heat, usually to remove water from a solution.

We will probably not be using evaporation today.

Procedure 6. Distillation

Distillation also takes advantage of differences in boiling point. In this case, the gas/vapor is captured again via condensation, rather than being allowed to escape into the air. A typical laboratory setup for distillation is shown in figure 3.13 on page 65 in the textbook.

n-distillation-apparatus

We will set up a distillation apparatus from a soda bottle that has been cut in half.

Place the homogeneous solution in the bottom of the soda bottle. Place an empty glass in the center. Then invert the top of the soda bottle (with the cap left on) into the bottom half. Press down so it fits tightly and doesn’t allow gases to escape. Fill the top of the soda bottle with ice. Cover with newspaper (insulation) and then aluminum foil. Set in the sun.

The water should evaporate from the bottom, condense on the top and then run into the cup.

__________________

Many other separation procedures are possible in chemistry. For example, in a future lab we will be using chromatography to separate pigments in ink.

Conclusions:

Once you have completed the separation, sit down and write a sentence or two to explain the results.

Discussion:

Record any thoughts you have about the experiments, including:

  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Suggestions for other experiments
  • What key concepts you learned about separating mixtures

We’ll go over the key concepts together at the end of lab.

If you would like to learn more, check this online chemistry lab from Phoenix College.

Please leave a comment or send an e-mail if you have any questions before our meeting.

Lab 2 Density of Solids and Measurement Challenge

Great job with your laboratory notebooks last week. Keep up the good work!

Today we are going to practice taking measurements using the techniques we learned in the lesson, plus investigate the density of solids. You will learn to make accurate measurements, estimate to the proper level of certainty, and apply rules for significant figures in calculations.

Experimental Title: Lab 2 Density of Solids and Measurement Challenge

Date of laboratory:  June 10, 2014

Purpose: The purpose of this laboratory is to measure the volume, mass and density of solid substances.

Introduction:  How to measure using estimation.

measurement-ruler

How would you measure the red line in this example? To take a measurement with the ruler above it, first you would count the spaces between the large numbers. There are 10 spaces in the example, so each space is 1/10 of the distance between the black-labeled marks. If the black marks represent centimeters, then each smaller mark is 1 millimeter apart.

The green mark just before the red arrow is 9/10ths of the distance between 7 and 8, which is 7.9 cm (or 79 mm).  Previously you might have reported the answer as 7.9 cm. In chemistry, however, you want to get a more accurate reading of this measurement because the red line actually extends past 7.9 cm. How do you do this when there aren’t any markings? Try to visualize 10 steps in the space between the 7.9 and 8.0. The easiest one to visualize would be 5 steps (5/10) or halfway between.  It is pretty clear the red arrow is less than halfway, so the length of the red arrow is less than 7.95 cm.

Now estimate halfway between 7.9 and 7.95. That would be 7.925, but you can’t see that accurately. The arrow is very close to half of the first half.  So, you could record the length as 7.92 or 7.93 cm, either one would be correct.

In summary, the first two digits (7.9) are measured without any estimation. They make 2 significant figures (also called significant digits). The last digit is an educated estimate, but it does give us more accuracy. Therefore, it is counted as a third significant figure. By estimating, you are getting a little more accuracy than what the markings read.

Don’t worry, this will become easier with practice.

Important equations:

Density can be calculated using the formula:

density= mass (g)/volume(mL or cm3)

Volume of a cube is   V= S3 where S = length of an edge

Volume of a rectangular prism is  V =lwh  where l is the length of the base, w is its width and h is its height

The volume of a triangular prism is V = AH  where A = the area of the triangular base or 1/2bh and H = the height of the prism

Special safety concerns for Lab 2:

  • If anything spills, please clean it up immediately with a paper towel and let your instructor know.
  • If glass breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands when you are finished with this lab

Materials:

  • Relational GeoSolid® blocks
  • Plastic blocks
  • Rubber stoppers
  • Sample of metal A
  • Sample of metal B
  • Sample of metal C
  • Sample rock
  • Water
  • Graduated cylinders
  • Table top scales
  • Transfer pipette
  • Rulers
  • Calculator

Procedures:

Note:  Today you can do the parts in any order, so go ahead to another part and come back to finish if you need to do so. No need to wait for materials.

Part 1. Determine the Volume of a CUBE and a Rectangular solid with a ruler

Last week we found the volume of a liquid using a graduated cylinder. This week we are going to find the volume of regularly-shaped objects by measuring and using mathematical formulas. Remember that a cubed centimeter is equal to 1 milliliter.

Procedure 1.

  1. Obtain a Relational GeoSolid® cube.
  2. Measure the length of a side in cm. Verify the shape is a cube by making sure the other sides are the same length.
  3. Record the length in your notebook.
  4. Using a calculator, calculate the volume using the formula V= S3.
  5. Record your answer using the correct number of significant figures.

cube-volume-table6. Repeat using the rectangular prism using the formula V =lwh.

prism-volume-table(Edit) 7. Now check the volumes you obtained by filling the Relational Geosolid® shapes with water.  Pour the water into a graduated cylinder and measure the volume.

Optional 1:  Obtain the solid triangular prism and calculate the volume using the formula V = AH where A = the area of the triangular base or 1/2bh and H = the height of the prism

triangular-prism-volume-tableWeigh the prism to obtain its mass. Measure the sides and calculate the volume. Now calculate the density. According to the text the density of glass is 2.6 g/cm3. Do you think the solid triangular prism is made of glass?

Let’s check to see if liquid volume is really equal to calculated volume.

8. Obtain a solid plastic cube (letter die)
9. Measure three sides to determine if it is a cube. If it is a true cube, then use the formula for volume V= S3 . If not, the use the formula for the volume V =lwh.
10. Record the side lengths and calculated volume.
11. Place 25 mL of water in a graduated cylinder. Carefully drop in the letter cube.
12. Record the final water level. Calculate the volume by subtracting 25 from the final level. How do the two volumes compare?

cube-2volume-table

Part 2. Determine the Density of an Irregularly-shaped object Using Water Displacement

Do you remember the density video from Lab 1? In it the narrator explained how to figure out a volume of an irregularly-shaped solid object by immersing it in water in a graduated cylinder and recording the difference in water level.

Procedure 2.

1. Obtain a small rubber stopper and a graduated cylinder.
2. Weigh and record the mass of the dry stopper. Use the more accurate smaller scale.
3. Use tap water to fill your graduated cylinder to 25 mL.
4. Read and record this volume to the nearest 0.1 mL remembering to read the volume at the bottom of the meniscus.
5. Carefully submerge the rubber stopper in the graduated cylinder.
6. Read and record the new volume. What is the volume of the rubber stopper?
7. What is the density of the rubber stopper?

Leave room to record your observations in your notebook.

Part 3. Identify unknown samples using density

  • Sample of metal A
  • Sample of metal B
  • Sample of metal C
  • Sample rock

Use what you have learned in the part 2 of this lab to calculate the density of metal samples and find out their identity. Be sure to take careful notes of what you do and what your results are.

Repeat procedure 2, replacing the rubber stopper with metal samples.

metals-density-table

Use this table of the density of some common substances to identify your unknowns.

Substance        Density (g/cm3)
Air                          0.0013
Wood (oak)          0.85
Water                     1.00
Ice                          0.93
Aluminum             2.7
Lead                        11.3
Copper                   8.96
Gold                        19.3
Iron                         7.86
Pyrite                       5.0
Galena                     7.5
Zinc                         7.133 – 7.14

(Edit) Optional 2. Measure the length, width and height of a wood block. Calculate the volume using V =lwh. Weigh the wood block. Now calculate its density. Is the wood block more or less dense than oak? Why is it preferable to calculate the volume of the wood block rather than use the water displacement method?

Final optional:  Obtain and weigh 5 dry pennies using the more accurate smaller scale. Now take their volume using the water method and calculate the density. Based on the density you obtained, do you think pennies are pure copper?

Please leave a comment or send an e-mail if you have any questions before our meeting.

Keeping a Chemistry Laboratory Notebook

A scientific laboratory notebook is an important document. In addition to being proof that you completed an honors high school chemistry laboratory, keeping an accurate notebook is also good practice for future classes and even jobs. A properly-formatted scientific notebook can serve as a legal document. For these reasons, we need to take keeping a laboratory notebook seriously.

Introduction:

To get started, please read Chapter 2 Keeping a Lab Notebook (pp. 15-18) in The Home Scientist Standard/Honors Home School Chemistry Laboratory Kit CK01A Instruction Manual (from now on, let’s call it “The Home Scientist Lab Manual.”)

Note a:  If the manual you downloaded doesn’t have this title or the page numbers don’t match, please let me know and I’ll help you find the right one.

Note b: For our notebooks, we are going to allow a few modifications from The Home Scientist Lab Manual guidelines, as stated below. You will find each class you take will have slightly different rules. You will need to follow those of your current instructor.

This Care and Feeding of a Lab Notebook video helps explain the steps as we will be using them.

His advice to do all the work in the laboratory notebook is good. There is no need to keep separate sheets and copy them neatly later.

The one exception is that we will not be signing and dating each page.

 

Instructions for Our Class:

1. The laboratory notebook must be permanently bound (not looseleaf). Those with quadrille-ruled pages are a good choice.

2. Always use ink, never pencil. For our purposes, I will allow and even encourage you to use different colors of inks. I really like how the “student” used different colors of ink in these sample laboratory notebook pages (from a college organic chem class).

3. When you make an error, simply put a single line through the words or numbers. The idea is to leave a permanent record of what you did. Never erase or use white out. Example of a notebook correction:  The water was hot. room-temperature

Note: Believe it or not, many important discoveries came out of laboratory errors. For example, an herbicide was discovered when a frustrated chemist threw his beaker of chemical out the window. Later he noticed that the mix had killed the grass, which he realized was a significant discovery. If he had “neatened up” his notebook by erasing, tearing out or other removing his experiment, he might not have been able to duplicate the formula.

4. Start out by numbering all the pages in order in the upper, outer corner. That means the right pages go in the top right corner and the left pages in the top left corner.

5. Create a title page. You can put a title on the front cover, but I recommend you also create a title page on the first page inside as well.

Example:

title-page-example

 

 

 

 

 

 

Note:  Do I need to tell you about the graduate student who accidentally put his notebook of his entire summer’s work on the roof of his car and drove for 30 miles? If your notebook is lost, it really pays to have your contact information inside!

6. Leave a few pages at the front to fill in the Table of Contents. It might look this when you complete it:

Table of Contents

Title                                                                                            Pages

Laboratory 1. Density of soft drinks                                    pp. 1-5

Laboratory 2. The Measurement Challenge                       pp. 6-12

etc.

7. Whether you use the right page only or both pages of the notebook is up to you. Using only the right page came about from the idea that ink might bleed through the paper, but since most paper these days is high quality, that is less of a problem than it once was. If you have a mixed note-taking and quadrille-ruled notebook, you might want to use the left side for notes and the right side for data.

8. You will need to record the name of your lab partner(s) and indicate their contribution for each lab. I like the idea of adding their name in a different-colored ink and writing their data in that color because it makes it very clear who did what parts. Different colors are not required, however.

9. You do need to put the date of each lab with the title as you start it. You do not need to sign and date each page. If you successfully complete the course, I will date and sign off on your notebook at the end of the course.

10. Add any printouts using glue sticks, not tape or staples.

11. We will follow the format for writing the labs in the notebook as suggested by The Home Scientist Lab Manual. I will also give you specific ideas and hints with each of the labs as we go along.

Inspiration:

Yes, I know keeping a rigorous laboratory notebook seems like a lot of work. You might be surprised, however, at how important keeping a detailed notebook as a journal of your work can be, regardless of what career you choose. For example. the famous designer Michael Bierut has filled 86 (!!) composition notebooks since 1982.

Do you have any questions? Please feel free to leave a comment on this blog, send a direct e-mail or post to our Yahoo group.