States of Matter & Energy Flow

WPHS Chemistry

Unit 6

States of Matter & Energy Flow

Bergmann-Sams

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Chemistry: Unit 6 Outline: States of Matter

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Assignment / In ClassOnly?
Podcast 6.1KMT and Pressure
Worksheet 6.1KMT and Pressure
Aluminum Can Crush
Podcast 6.2 Vapor Pressure and Phase Diagrams
Demo: Boiling Water with Ice / 

Worksheet 6.2Vapor Pressure and Phase Diagrams

Demo: Triple Point of CO2
Podcast 6.3 Energy Transformations
Worksheet 6.3 Energy Transformations
Lab: What factors affect heat flow?
Podcast 6.4 Heat Capacity
Worksheet 6.4 Heat Capacity
Lab: Heat Capacity of a Metal
Podcast 6.5 Energy Stoichiometry
Worksheet 6.5 Energy Stoichiometry
Podcast 6.6 Calorimetry
Worksheet 6.6 Calorimetry
Lab: Heat of Reaction: Magnesium / 
Podcast 6.7 Phase Change Problems Conceptual
Worksheet 6.7 Phase Change Problems Conceptual
Demo: Burning Paper with Steam / 
Podcast 6.8 Phase Change Problems Mathematical
Worksheet 6.8 Phase Change Problems Mathematical
Lab: Heat of Fusion of Ice / 
Unit 6 Vocabulary
Lab Test: Finding ∆H / 
Unit 6 Exam / 

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Unit 6: Vocabulary

Kinetic theory

Kinetic energy

Gas pressure

Vacuum

Atmospheric pressure

Barometer

Pascal

Standard atmosphere (atm)

Vaporization

Evaporation

Vapor pressure

Boiling point

Normal boiling point

Melting point

Crystal

Allotropes

Amorphous solids

Phase diagram

Triple point

Sublimation

Thermochemistry

Energy

Chemical potential energy

Heat

System

Surroundings

Universe

Law of conservation of energy

Endothermic process

Exothermic process

Calorie

Joule

Heat capacity

Specific heat

Calorimetry

Calorimeter

Enthalpy

Thermochemical equation

Heat of reaction

Heat of combustion

Molar heat of fusion

Molar heat of solidification

Molar heat of vaporization

Molar heat of condensation

Molar heat of solution

Heat of formation

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Title: Aluminum Can Crush—Take Home Lab

Subject/Concept: Chemistry - Gas Laws

Purpose: The purpose of this activity is to observe the gas laws in action.

Materials: •1/8 cup water

• small pan of ice water

• 1 empty aluminum soda can

• 1 pair barbeque tongs

• 1 stove

Procedure:

1. Place 1/8 cup of water in an empty aluminum soda can.

2. Heat the can of water on the stove on medium until visible steam escapes from the can for a period of about 5-10 seconds.

3. With the barbeque tongs, grab the can and invert it into the pan of ice water.

Cautions:

1. Do not boil the can dry! It will melt onto the stove top!

2. Do not touch the aluminum cans with your hands while it is on the stove. It is very hot.

3. Be careful not to spill or splash any of the boiling water in the can as you invert it.

Questions:

1. What gas replaces the air while the water is boiling?

2. What is the chemical formula for the gas in question #1?

3. Explain how each of the following contributes to the results:

a) the temperature of the gas cools when the can is removed from the heat

b) the gas inside the can condenses to form water droplets

4. What is the difference between an implosion and an explosion?

5. If cans are roughly 8” in circumference and 4.75” tall, how many pounds of pressure does the atmosphere place on the outside of the can? (1 atm = 14.7psi )

For Credit:

To receive credit, your parent or guardian must write a short note confirming that you performed the experiment for them and explained the results to their satisfaction using the concept of gas laws. Attach your note to the back of this sheet.

Lab: What factors affect heat flow?

Pre-Experiment Discussion

Chemical and physical changes are always accompanied by a change in energy. Most commonly this energy change is observed as a flow of heat energy.

Previous Knowledge:

Understand basics of heat transfer
Knowledge of types of energy

Questions:

Two objects with different temperatures are touching. Describe the heat flow.
Which direction does the heat flow? Why?

How will the temperatures of each object change?

When will the heat flow cease?

What will the final temperatures be?

Discuss with your group the Question of the Day. Present a summary of your ideas to the rest of the class.

Materials:

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beaker, 400-mL

Bunsen burner/hotplate

wire gauze

ring stand

test tube tongs

electronic balance

4 materials in small pieces

test tube, large

thermometer

graduated cylinder, 100-mL

Styrofoam cups, 2, with lid

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Safety Alert:

All materials being used around the Bunsen burner should be assumed to be hot. Metal and glass looks the same hot as it does cold. Use heat resistant gloves to handle hot objects.

Wear Safety Goggles the entire time!

Procedure:

Set up your Bunsen burner, wire gauze, and ring stand. Fill your 400-mL beaker about 4/5 full of tap water. Set it on your wire gauze. Light the Bunsen burner so the water can be heating as you prepare the sample of metal.
Using the electronic balance, obtain about _____ g of the ______. Record the exact mass on your data table. Put an X in the box for the sample that you will be studying.** other ideas: sand, soil, antifreeze, water,

Masses
Substances / 40 g / 60 g / 80 g
Aluminum
Copper
Zinc
Glass

Add the substance to your large test tube. Put your thermometer in the middle of the pieces so it can track the temperature of the sample. It might be easier to add some pieces, then insert the thermometer, and then add the rest of the metal pieces around it.
Gently place the test tube in the warm water. Be sure that the entire sample of the substance is below the water line. Answer In-Lab Question #1.
Prepare your calorimeter by stacking two Styrofoam cups together.
Measure exactly 100 mL of tap water into the calorimeter.
Insert your second thermometer into the opening in the lid of your calorimeter. Record the temperature of your water in the data table.
Allow the metal to reach a temperature between 85 and 90 °C. Measure and record the exact temperature of the metal in the test tube in your data table.
Answer In-Lab Question #2. Work quickly but carefully: remove the lid of the calorimeter and empty the hot metal from the test tube into the calorimeter. Replace the calorimeter lid and thermometer. Set the test tube aside.
Answer In-Lab Question #3. Gently swirl the mixture of metal and water in your calorimeter. Watch the reading on the thermometer. Record the highest temperature reached for the mixture in your data table. Answer In-Lab Question #4.
To cleanup, remove the thermometer from the calorimeter. With the lid on your calorimeter to catch the metal pieces, pour the water into the sink. Put the wet metal caught in the lid in the labeled container to dry.
Repeat Steps 1-11 two more times.

In-Lab Questions:

Discuss and answer questions with your partner at the appropriate times noted in the procedure.

Is the temperature of the metal before heating important? Explain.

Why would the hot metal need to be transferred to the water quickly?

What is the purpose of the swirling?

What would happen to the temperature of the mixture if it was allowed to sit longer? Explain.

Data Table

Pair Data Collected
Type of Substance
Trial 1 / Trial 2 / Trial 3
Mass of substance / g / g / g
Temperature of water / °C / °C / °C
Temperature of substance / °C / °C / °C
Temperature of mixture / °C / °C / °C

Post-Experiment Questions:

Discuss and answer questions with your partner at the appropriate times noted in the procedure. After you have finished, compare your answers with the other members of your larger group and discuss any differences.

Which part of the mixture, the substance or the water, was releasing heat? Which was absorbing heat? How do you know?

What can you say about the final temperature of the objects?

Calculate the change in temperature of the water for each trial and then calculate the average of these values.

Calculate the change in temperature of the metal for each trial and then calculate the average of these values.

Compare the change in temperatures of the three metal samples. Describe any trend you find.

Propose a hypothesis for the pattern you have observed.

Compare the change in temperature of the water to the change in temperature of the metal. Describe any trend you find.

Propose a hypothesis for the pattern you have observed.

Create one line graph of mass of metal vs. the inverse of the average change in temperature of the metal (mass vs. 1/∆T) for each of the four metals. Make each of the four lines a different color. Add a line of best-fit for each metal and display the equation on the chart.

Discuss with your group the meaning of the slope. Summarize your ideas here.

Which metal has the highest slope? Which has the lowest slope?

What do these differences suggest about how these metals transfer heat?

Based on the data from this experiment, summarize the factors that affect heat transfer.

Brainstorm properties of the different materials that might account for their different heat flow behaviors.

Using grammatically correct sentences compare the heat transfer ability of each material tested.

If a similar experiment was done using 100 mL of water at 20°C with 100 g of metal at 80°C, what would you expect the approximate final temperature to be? Explain.

Assuming an island and inland areas or exposed to the same amount of heat energy, why would the island have less drastic temperature changes than inland area?

How would you determine Styrofoam’s ability to transfer heat? What difference, if any, would you find in its behavior compared to metal? What is a common use of Styrofoam that capitalizes on this idea?

If 5 g samples of glass and copper are placed on the same hot plate and allowed to heat for one minute, how would their final temperatures compare? Explain.

Reflecting on what you have learned throughout the experiment, summarize what you have learned about heat transfer.

WPHS Chemistry
Identification of an Unknown Metal

In this lab we will be using lab techniques and basic chemical concepts to identify an unknown metal. Every metal has a unique set of properties. We will be using specific heat (also known as "heat capacity" or "specific heat capacity"). Your periodic tables have adequate listings for the purpose of this experiment, but several other sources also have listings of these values for pure materials: check the indices of the CRC Handbook, the Merck Index, or the Exploring the Elements books on the shelves around the room.

NOTES: Goggles are necessary, and long hair must be tied back . Record all data to the correct decimal place in your lab handbook. Since we are using digital thermometers, feel free to stir with the thermometer.

PROCEDURE - Specific Heat
To determine the specific heat of a metal sample, we will use a calorimeter, and the concept that in a closed system, heat lost by a hot object is gained by a cooler one.

mCp∆T (cold) = –mCp∆T (hot)

To determine the initial (high) temperature of your metal sample, suspend it in a beaker of boiling water and keep it there until boiling has proceeded steadily for about two minutes. Record the temperature of the boiling water with a thermometer in a rubber stopper (it should not touch the beaker glass). This is the same as the initial metal temperature.

While the water/metal mixture is boiling, record the mass of the empty calorimeter cup. Next, add just enough water to cover your piece of metal (estimate), and determine the combined mass. Keep track of the temperature of this water with a second thermometer.

Record the temperature of the cold water and of the metal just before combining them. Immerse the metal sample in the cold water and record the final temperature of the mixture. It should change quickly at first, then level off, then cool back down slowly. Record the level part.

NOTE: Perform one density trial then one specific heat trial, then repeat the whole thing two more times. Make sure Everything is dry for each trial.

Data Table

Trial 1 / Trial 2 / Trial 3
initial temperature of metal / ______/ ______/ ______/ (C)
temperature of cold water / ______/ ______/ ______/ (C)
final temperature of mixture / ______/ ______/ ______/ (C)
specific heat of water / 4.18 / 4.18 / 4.18 / (J/gC)
mass of cold water (use Vol) / ______/ ______/ ______/ (g)
change in water temperature / ______/ ______/ ______/ (C)
change in metal temperature / ______/ ______/ ______/ (C)
specific heat of metal / ______/ ______/ ______/ (J/gC)

Show a complete sample calculation for heat capacity and then determine which metal you have using the table below

Metal / Specific Heat (J/g ºC) / Metal / Specific Heat (J/g ºC) / Metal / Specific Heat (J/g ºC)
Aluminum / 0.91 / Antimony / 0.21 / Carbon Steel / 0.49
Cast Iron / 0.46 / Copper / 0.39 / Gold / 0.13
Iron / 0.46 / Lead / 0.13 / Magnesium / 1.05
Molybedenum / 0.25 / Nickel / 0.54 / Sliver / 0.23
Tin / 0.21 / Titanium / 0.54 / Zinc / 0.39

Heat of Reaction of Magnesium

Description

The mass of a measured length of polished magnesium ribbon is determined. A small length of ribbon is cut and its length measured. From the length of the small piece, its mass is calculated. A known volume of acid is placed in a calorimeter. The temperature is measured. The magnesium is added to the calorimeter, and a reaction takes place. The temperature is measured once reaction ceases. From the mass of ribbon reacted, the temperature increase, and the volume of acid used, the heat of formation of Mg2+(aq) is determined.

Hazards

Magnesium burns in a very exothermic reaction. Never look directly at burning magnesium. Cuts when polishing the magnesium metal are possible. The dilute acid is corrosive.

Precautions

Keep magnesium away from ignition sources such as open flames. Wear gloves when polishing the magnesium metal ribbon. Wear eye protection; wash acid spills immediately.

Procedure

Demonstration:

Place 100 mL of 3 M hydrochloric acid in a 250-mL beaker. Fold a 10-cm length of magnesium ribbon, place in the solution, and note evidence for reaction.

Experiment:

Carefully measure and record the length of one of the cut pieces of polished magnesium ribbon. Obtain the mass of a 1.00 meter length of polished magnesium ribbon from your instructor.
Crumple the piece of magnesium into a small ball.
Pour 50-60 mL of 3 M hydrochloric acid into a 100-mL cylinder. Measure and record the exact volume to the nearest 0.2 mL.
Assemble a calorimeter.
A calorimeter assembled from three foam cups works well. Two nested cups hold the fluid. One fourth of the third cup is removed at the lip. A hole is made in the bottom for the thermometer; a hole is made in the side near the upper edge through which additions can be made. When inverted, this piece serves as a calorimeter cover.
Pour the measured volume of acid into the inner calorimeter cup. Cover. Insert the thermometer. Read and record the temperature to the nearest 0.1 °C at regular intervals until it becomes constant.
Add the crumpled magnesium to the acid solution. Swirl gently. Note the temperature.
Record the maximum temperature reached by the hydrochloric acid solution.

Data

length magnesium ribbon (cm)
mass Mg/ m (provided by instructor)
mass Mg used
mol Mg used
volume HCl (mL)
initial temperature, °C
maximum temperature, °C
temperature rise, °C
energy released (J)
energy released/ mol Mg (kJ/mol)
Percent Error

Accepted value = -462.0 kJ/mol at 25 °C for 1 M H+

Write an equation for the reaction of magnesium metal with hydrochloric acid. Include the heat of reaction calculated above.
State the relationship between the heat of reaction for this reaction and the heat of formation of aqueous magnesium ion.
The accepted heat of formation of Mg2+(aq) is -462.0 kJ/mol (25 °C, 1 M). Find the percent error for the experiment

Heat of Fusion of IceName

INTRODUCTION:

The amount of energy required to convert a solid to a liquid, at constant pressure and temperature, is called the heat of fusion of the substance. In this experiment, the heat of fusion of ice will be determined.

The ice will be melted by placing it in a known volume of hot water contained in a plastic cup. The system will be left undisturbed until all the ice has melted. The amount of heat lost by the hot water in this process can be calculated according to the following equation.

Procedure

Get 100.0 mL of water at the highest temperature you can out of the tap.
Place the water in a Styrofoam cup.
Measure the temperature of the water.
Simultaneously, the other partner should be getting a handful of ice cubes that need to be dried.
Place the ice cubes in the cup of hot water and wait until the ice cubes have completely melted.
Measure the final temperature.
Measure the total volume of the cool water.
Place all data in the table below.
For the masses: Assume that the density of water is 1.0 g/mL.

DATA TABLE:

Initial mass of hot water.
/ g
Initial temperature of hot water.
/ ºC
Final temperature of water and melted ice.
/ ºC
Final mass of water and melted ice. / g
Change in Temp of Hot Water / ºC
Change in Temp of Ice / ºC
mass of ice added / g

Calculations