GPS UNIT PLANCHEMISTRY: GAS LAWS

Nancy Brim Grade Level: 10/11Lakeside High School Length of unit: 13 days (non-block)

Contact InformationNancy_H_Brim@fc.deKalb.k12.ga.usHandouts found at http://nancyhbrim.wordpress.com/about/. Click on Assignments for Second Semester.

Brief Summary of the Unit:Students will compare and contrast gases with solids and liquids. Students will determine the

relationship between pressure, temperature, volume, and moles.

STANDARD Co-Requisite – Characteristics of ScienceSCSh1. Students will evaluate the importance of curiosity, honesty, openness, and skepticism in

science.a. Exhibit the above traits in their own scientific activities.b. Explain that further understanding of scientific problems relies on the design and execution of

new experiments which may reinforce or weaken opposing explanations.SCSh2. Students will use standard safety practices for all classroom laboratory and field

investigations.a. Follow correct procedures for use of scientific apparatus.b. Demonstrate appropriate techniques in all laboratory situations.c. Follow correct protocol for identifying and reporting safety problems and violations.

SCSh3. Students will identify and investigate problems scientifically.a. Collect, organize and record appropriate data.b. Graphically compare and analyze data points and/or summary statistics.c. Develop reasonable conclusions based on data collected.

SCSh4. Students will use tools and instruments for observing, measuring, and manipulating scientific equipment and materials.

a. Develop and use systematic procedures for recording and organizing information.b. Use technology to produce tables and graphs.

SCSh5. Students will demonstrate the computation and estimation skills necessary for analyzing data and developing reasonable scientific explanations.

a. Consider possible effects of measurement errors on calculations.b. Recognize the relationship between accuracy and precision.c. Express appropriate numbers of significant figures for calculated data, using scientific notation

where appropriate.d. Solve scientific problems by substituting quantitative values, using dimensional analysis,

and/or simple algebraic formulas as appropriate.SCSh6. Students will communicate scientific investigations and information clearly.

a. Write clear, coherent laboratory reports related to scientific investigations.SCSh8. Students will understand important features of the process of scientific inquiry.

Students will apply the following to inquiry learning practices:a. Scientific investigators control the conditions of their experiments in order to produce valuable

data.

b. Scientific researchers are expected to critically assess the quality of data including possible sources of bias in their investigations’ hypotheses, observations, data analyses, and interpretations.

CHEMISTRY ContentSC6. Students will understand the effects motion of atoms and molecules in chemical and

physical processes. SC2. Students will relate how the Law of Conservation of Matter is used to determine chemical

composition in compounds and chemical reactions.

Big Idea: Gases as a phase of matter

Elements: a. Compare and contrast atomic/molecular motion in solids, liquids, gases, and plasmas.

c. Apply concepts of the mole and Avogadro’s number to conceptualize and calculate Mass, moles and molecules relationships Molar volume of a gas

d. Identify and solve different types of stoichiometry problems, specifically relating mass to moles and mass to mass.

Enduring Understandings:1. Gases have no definite shape or volume and will fill any container they are in. 2. Gases are affected by pressure, temperature, volume, and moles

Essential Questions:1. What is pressure?2. How are pressure, and volume, volume and temperature, temperature and pressure, and volume and

moles related?3. How does mass affect the velocity of a particle of gas?

Skills:1. Students will be able to solve for Boyle’s Law, Charles’ Law, Gay-Lussac’s Law, Avogadro’s Principle,

the Combined Gas Law, the Ideal Gas Law, Graham’s Law of Diffusion, and Dalton’s Law of Partial Pressures.

2. Students will understand when ideal gases behave as real gases.3. Students will be able to solve for Density and Molar Mass using the Ideal Gas Law.4. Students will be able to use the molar volume of a gas to solve stoichiometry problems.

EVIDENCE OF LEARNINGPerformance Tasks:

1. Students will explore the relationship between volume and pressure.2. Students will explore the gas laws with balloons, cans, and straws3. Students will explore and calculate Graham’s law of Effusion.4. Students will explore phase changes and chemical reactions through dry ice.

LEARNING EXPERIENCE AND INSTRUCTIONDAY 1:

Objective: Discuss pressure, atmospheric pressure, and pressure unitsActivity: LECTURE: Pressure

LAB: Gas PressureDAY 2:

Objective: Develop the gas laws demoing the relationship between pressure, temperature, and volume and solving problems.

Activity: DEMONSTRATION: Boyle’s, Charles’, and Gay-Lussac’s demosLECTURE: Gas characteristics, Boyle’s, Charles’, Gay-Lussac’s Laws.

PRACTICE: Calculating for missing temperature, pressure, and volume.DAY 3:

Objective: Exploring the gas lawsActivity: LAB: Playing with Cans and Balloons

DAY 4:Objective: State and Use Dalton’s Law of partial pressures; Perform calculations using the combined and

ideal gas laws.Activity: DEMONSTRATION: Dalton’s law of Partial Pressures

LECTURE: Avogadro’s Principle, Dalton’s Law of Partial Pressures, Combined Gas Law, Ideal Gas Law

PRACTICE: Dalton’s Law of Partial Pressures, Combined Gas Law, Ideal Gas LawDAY 5:

Objective: State and Use Graham’s Law, Explain how real gases differ from ideal gases; Apply the concept of Molar Volume in stoichiometry calculations

Activity: DEMONSTRATION: Graham’s Law with anis and cinnamon oilLECTURE: Graham’s law, real versus ideal gases, gas stoichiometryPractice: Graham’s Law and Gas Stoichiometry.

DAY 6:Objective: State and Use Graham’s Law of DiffusionActivity: LAB: Rates of Diffusion of Gases

DAY 7:Objective: Solve problems involving P, V, T, and molesActivity: PRACTICE: Gas Laws Problems

DAY 8:Objective: Calculate the density and molar mass of a gas using the ldeal gas lawActivity: LECTURE: Density and molar mass

PRACTICE: Density and Molar Mass DAY 9:

Objective: Solve problems involving P, V, T, and molesActivity: PRACTICE: More Gas Laws Problems

DAY 10:Objective: Solve problems involving P, V, T, and molesActivity: LECTURE: Solution equilibria

ASSESSMENT: Gas Laws QuizDAY 11:

Objective: Explore the Properties of Dry IceActivity: DEMONSTRATION: Dry Ice Pressure Builder, Candles and Bubbles in tank

LAB: Dry Ice DayDAY 12:

Objective: Review the objectives for the unitActivity: DISCUSSION/PRACTICE: Review of unit objectives

DAY 13:Objective: Display knowledge of unit objectivesActivity: ASSESSMENT: Unit test

DemonstrationsPRESSUREPressure is force per unit area - like N/m2

Materials: square meter of cloth 2 pkgs Fig Newtons spring scale

1. 6 fig newtons = 1 Nshow this by placing 6 Fig Newtons in a plastic bag and hanging it from the spring scale.

2. 1 N/m2 - Spread the 6 Fig Newtons out on the cloth NOT MUCH FORCE3. 1 Kpa = 6000 Fig Newtons/m2

put the 60 Fig Newtons (in a bag on the cloth and tell them the force is 10x this.4. 101.3 Kpa = 608000 Fig Newtons

This is atmospheric pressure – what is pushing down on you right now.FYI: 600,000 Fig Newtons (if laid on top of each other) would be 29 feet high!

GAS LAWS Boyle’s Charles’ Gay-Lussac’s Balloon and bottle Hot and cold flask Boil water under Cartesian diver with balloon lowered pressureEgg in BottleGiant SyringeVacuum pump – Marshmallows, gel

GRAHAM’S LAWMaterials: Hot plate, cinnamon oil, anise oil, 250 mL beaker of water, 2 pipetsProcedure:

1. Fill beaker 2/3 full water and heat to boiling2. Pipette a few drops of each oil into the beaker (Do not tell the identity.).3. They will smell the anise first and then the cinnamon. Get them to see that in order to

maintain equality, the faster velocity must have the smaller mass if KE = ½ mv2

Questions:1. What can we assume about the temperature of the two oils in this beaker of boiling water?

TA = TC

2. How is temperature related to kinetic energy? Temp is average KE3. How do the kinetic energies of the two oils compare? KEA = KEC

4. What is the formula for KE? KE = ½ mv2

½ mAvA2 = ½ mCvC

2

½ mAvA2 = ½ vC

2

mC

½ mA = ½ vC2

mC vA2

mA = vC2

mC vA2

mA = vC

mC vA

Name _________________________________ Period ___ Date _______________________

Partner _______________________________________

GAS PRESSURE

Purpose: Observe the effect of increase pressure on the volume of a confined gas.Graph the pressure to volume relationshipDescribe the pressure to volume relationship in mathematical terms.

Background: The volume of a gas depends on three factors: 1.) The number of moles of the gas; 2.) the temperature at which the volume is measured and; 3.) the pressure. For measurements at constant temperature, there is a simple mathematical relationship between the volume of a gas and the pressure. This relationship is known as Boyle’s Law in honor of Sir Robert Boyle, the British chemist who first recognized it about 300 years ago. This activity's purpose is to discover the relationship between pressure and volume of a gas.

Materials: metric ruler pipet 8 same size books

Procedure:1. Form a hypothesis to explain what would happen to the volume of a gas as the pressure is increased

or decreased.

The Experiment:2. Place two equal-sized books on the bulb of the pipet. The stem of the pipet should be visible as

shown in the diagram.3. Measure the column length of the trapped air in the stem of the

pipet in millimeters (watch sigfigs) and enter this measurement in the data table.

4. Place another book on top of the first two, and measure and record the length of the air column again.

5. Continue to add the remaining books to the stack one-by-one. Measure and record each new air column length in data table.

Data and Observations

Pressure (books) Air Column Length (mm) Pressure (Books) Air Column Length (mm)2 6

3 7

4 8

5

Analysis and Conclusions:1. Plot your data on the first graph grid provided by your teacher. Use the pressure in books as the X

variable and the length of the column of air as the Y variable. Be sure to put a title on your graph, start at zero, and use the WHOLE graph! Is the relationship between gas pressure and volume linear? (circle one) YES NO

2. Was your hypothesis correct? Explain why or why not.

3. Calculate the inverse of the pressure, 1/pressure, in books (i.e. ½, 1/3, ¼). NO FRACTIONS – convert numbers!!! Use the length of air column from your data table. Enter in table below.

1/Pressure 1/Pressure Air Column Length (mm) 1/Pressure Air Column Length (mm)

4. Plot the second graph. Use the inverse, 1/pressure, as the X variable and the length of the air column as the Y variable. Be sure to put a title on your graph, start at zero, and use the WHOLE graph! Is the relationship between 1/pressure and the volume of gas linear?

YES NO

5. What generalization can you make about the effect of increased book pressure on the volume of the confined gas?

6. Write a mathematical equation for the relationship between pressure and volume of a gas as constant temperature. Use P for pressure, V for volume, and K for any necessary constant. Start with “K =”.

7. What would happen to a gas under extremely high pressures or extremely low temperatures?

8. If a pressurized gas is released from a vessel, ice can be seen forming on the outside of the vessel. Why does this happen?

Names _________________________________________________ Period _____ Date _________________________

________________________________________________

PLAYING WITH CANS AND BALLOONS

We are beginning the section on the Gas Laws. These are laws that deal with how pressure, temperature and volume are interrelated when used with gases.

For each of the activities, do the following. I am looking for a thoughtful analysis of each situation, using the gas laws as a basis around which to form your intelligent well-reasoned responses.

A. Record all observations in paragraph form. Please make detailed observations, above and beyond what is specifically asked for.

B. For the conclusion for each experiment, explain why you observed what you did. If you can determine a relationship between temperature and pressure, temperature and volume, or volume and pressure, say what that relationship is. If a gas law applies, give the name of the law and how it applies. Do not just state the definition of the law, but rather state how this law specifically applies to each situation.

You will turn in one lab for each lab group. This sheet should be on top with the answers in chronological order attached. No title page is required. Each member in the group should initial which responses they answered.

WEAR GOGGLES FOR THESE1. Too Hot to Touch: Pour about 25 mL of water into a soda can. Fill the white bucket ¾ full of water and

add one cup of ice. Place can on a ring stand with an iron ring and wire gauze and heat to boiling. After steam has been rising out of the can for several minutes, firmly grasp the can with the beaker tongs. Quickly invert the can (open end down) and submerge into the bucket of ice water. Make observations of what happened while heating and once the can is placed in the bucket.

2. An Utterly Deflating Event: Place about 10mL of very hot water (get from the back desk) in a large test tube and attach a balloon to the test tube. Heat the water to boiling (don’t melt the balloon!). Make observations. Quickly plunge the test tube into the bucket of ice water. Make observations.

YOU CAN TAKE YOUR GOGGLES OFF IF THE PEOPLE ACROSS FROM YOU ARE ALSO FINISHED WITH #1 AND #2.3. Up, Up, and Away: Blow up a balloon all the way. Feel the surface of the balloon and note the

temperature of the balloon. Make observations. Quickly deflate the balloon and note its temperature. Make observations.

4. Can You Pull Enough? Fill a clean cup with water. Take a sip of water with the straw. Make observations. Using scissors, cut out a small piece of the straw above the water surface. Then drink out of the straw again and make observations.

5. From a Stream to a Trickle: Fill a two liter bottle with water, keeping a finger over the hole at the base. Inflate a balloon and attach to the top of the bottle. Remove your finger from the hole holding the bottle over the sink. Make observations. Remove the balloon. Fill the bottle again with water, attach a deflated balloon, and remove your finger from the hole while holding the bottle over the sink. Make observations.

RATES OF DIFFUSION OF GASES

BACKGROUND: Even if you are in another room, you can tell when someone has sliced a lemon or opened a bottle of vinegar in the kitchen. Particles of the juice or the vinegar escape into the air and move through it. This movement of particles of one substance through another medium, in this case, air, is called diffusion. The moving particles have kinetic energy, the energy of motion. While all type particles have the same kinetic energy at a given temperature, not all particles diffuse at the same rate. Heavier particles move more slowly than lighter particles.

This relationship, called Graham’s Law, states that if the temperature and pressure of two gases are the same, the rates of diffusion of those gases will be inversely proportional to the square root of their masses.

The equation is v1 = m2

v2 m1

“v” is velocity and “m” is mass in one mole

In this experiment, you will observe a reaction between two gases and determine the relationship between molecular mass and rate of diffusion.

OBJECTIVES: Measure the relative distance moved by two gases.Calculate the ratios of masses and the velocities of the two gases. Compare the two ratios.

MATERIALS: goggles glass tubing cotton swabshydrochloric acid ammonia metric rulerclear tape transparency pen

SAFETY: Wear goggles at all time. Concentrated HCl and ammonia can burn the skin and damage clothing. Handle both liquids with care. Do not leave either unstoppered for very long. If spills occur, notify your teacher immediately. Be careful with the glass tubing. It is awkward to carry and very easy to break. Wash your hands when you finish.

PROCEDURE:

1. Make a hypothesis based on the question: “Which gas will diffuse faster, hydrochloric acid or ammonia?” Start out with “If two gases, ammonia and hydrochloric acid, are released at the same time, then…”. Write your hypothesis in your logbook for now and then transfer it to the section above the ‘Data and Observations’ on your labsheet.

2. Secure the two glass tubings on the counter with a piece of clear tape near each end. Label one end NH3 (use the laminated sign) and assume the other end is HCl.

3. Take a cotton swab and soak the tip in the HCl. Do the same for another swab in the NH3. Recap the bottles. CAUTION: HYDROCHLORIC ACID AND AMMONIA ARE CORROSIVE. Keep stoppers in when not in use.

4. Carefully, AND AT THE SAME TIME, insert the soaked end of the swabs into opposite ends of the first glass tube by holding the cotton swabs by the dry end. Be sure that you match each swab with the appropriate label that you placed at the end of the tube. With a transparency pen, mark the tubing at the tip of each cotton swab.

5. Do not disturb the glass tubing or the swabs as the reaction takes place. (It will take several minutes). The reaction forms a white ring where the two gases meet.

6. With a transparency pen, mark the tubing at the spot of the reaction.7. Remove the swabs, rewet them (be sure to rewet using the right bottle!!!) and place

them in the ends of the second tube. Be sure that you match each swab with the appropriate label that you placed at the end of the tube. With a transparency pen, mark the tubing at the tip of each cotton swab.

8. Measure the distance from the mark (in centimeters – watch your sig figs!) for each cotton swab to the mark of the reaction ring for the first tube. Record these distances in the Data and Observations section.

9. Clean the tube by wetting the outside to get the transparency pen’s marks off and then using a beaker, pour water down the inside of the tube. Bring the wet, clean tube to back desk for drying.

10. Repeat steps 2-9 for a second trial using the second tube. 11. Once you have done both of your trials, record your data for the class. The class

average will be calculated and reported to you.

Name ______________________________ Period _____ Date __________________

RATES OF DIFFUSION OF GASES

HYPOTHESIS:

DATA and OBSERVATIONS:

Trial 1 Trial 2 Class AverageDistance HCl moved (cm)

Distance NH3 moved (cm)

Calculate the molar masses for each of the gases. Show your work.HCl

NH3

ANALYSIS and CONCLUSION:

1. Calculate the ratio of the distance moved using the CLASS AVERAGES. Since both gases moved through the glass tube in the same amount of time, the distances the gases moved can be used as a measure of the rates of diffusion of the gases. Substituting the distance (d) each gas moved for the velocity of the gas. Determine the ratio of the distance moved. Show your work. This is the experimental ratio.

d1 = m2 HCl = distance NH3 traveled Exp. Ratio: _________________ d2 m1 NH3 distance HCl traveled

2. Determine the true rate of diffusion for Molar Mass ratio: _________________

ammonia (m1)to hydrochloric acid (m2). Use the masses from the periodic table. Write the formula and show your work.

3. How close is your experimental value to the Percent Error: ___________________molecular mass ratio? Calculate your percent error. Write the formula and show your work.

According to your laboratory findings:4. Which molecule had the greater velocity? ____________________________

5. Which molecule has the greater mass? ____________________________

6. Express in words, the relationship between m (mass) and d (distance) for gases. (Hint: Remember the point of this lab!!)

7. Did your results support your hypothesis? EXPLAIN.

Name__________________________________ Period_______ Date__________________

DRY ICE DAYWhere does dry ice come from? Dry ice is carbon dioxide gas (CO2) that has been solidified

under very high pressure. It’s temperature is approximately -79C - that’s very cold! Most gases exist because of the very low degree of intermolecular attractions between the molecules. Solid carbon dioxide sublimes at room temperature, meaning that it goes directly from a solid to a gas without passing through the liquid phase. Dry ice (under normal pressures) never melts to form a liquid…hence the name Dry Ice. The most common use for dry ice is in shipping, because it keeps things cold without the hassle of a liquid residue. Today’s lab will focus on the behavior of dry ice in various circumstances. It is important that you write down your observations as you complete each procedure. Your dry ice needs to last seven experiments. Plan wisely!

DRY ICE SHOULD BE HANDLED WITH GREAT CAUTION. DO NOT TOUCH THE DRY ICE WITH YOUR BARE HANDS. DOING SO MAY RESULT IN FROSTBITE ALWAYS USE YOUR SPOON AND GLOVES TO MANIPULATE THE ICE.

PROCEDURE:

1. Bring your large beaker to your teacher to obtain your dry ice. Take it back to your lab table. Observe the ice and then place the bowl of a spoon on top. Record your observations in the space below.

2. Put a few pieces of dry ice in an Erlenmeyer flask. Stretch the mouth of a large balloon over the mouth of the flask and dump the dry ice into the balloon. Remove the balloon and tie a knot. Observe the ice and record your observations. Bring balloon to the box up from when you are finished..

3. Place a small piece of dry ice and a small piece of regular ice on the lab table. With one push, propel the regular ice across the table to your partner. Repeat the procedure with the dry ice and record your observations in the space below.

4. Place a few pieces of dry ice in a half full cup of water. Observe and record observations. You can pour all liquids down the sink.

5. Fill a plastic cup half full with water. Squirt a small amount of dishwashing soap into the water. Place a piece of Dry ice into the soapy water and record your observations.

6. Fill two cups half full with tap water. Place 10 drops of Bromothymol Blue in one cup and 10 drops of Universal Indicator in the other. Drop a few small pieces of Dry ice into each container and record your observations.

7. Fill a 100ml-graduated cylinder with tap water to the 100mL mark. Place the graduated cylinder on a paper towel and then add about 20 drops of Universal Indicator, and 10 drops of NaOH solution. Place a folded paper towel over the top and put your palm on top of that and invert the graduated cylinder to mix the liquids. Place 2 or 3 pieces of Dry ice into the cylinder and record your observations.