LABORATORY 1: HEAT TRANSFER AND PHASE CHANGES Objectives: 0 to predict how energy will ow when objects are heated or cooled, or for objects in contact that have different temperatures a to explain why some materials hold and release more energy than others for the same difference in temperature 0 to connect particle-level descriptions of matter, including different phases, with macroscopic observations/properties o to describe how heating or cooling changes the behavior of the molecules 0 to relate a pressure-temperature diagram to the behavior of molecules Materials Required: Computer with Excel and access to simulations: 0 Energy Forms: hgpsz/lphetcolorado.edu/en/simulation/energyformsandchanges and 0 States of Matter: hgsz/phetcolorado.edu/en/simulation/statesofmatter Software Requirements: Windows Macintosh Chromehook Linux iPad Mobile Phone Chrome, Edge Chrome, Safari Chrome Not recommended Safari Not recommended Introduction: The Specic Heat of a substance, usually indicated by the symbol C, is the amount of heat required to raise the temperature of one gram of the substance by 1 C (or 1 K). If an object is made of a substance with specic heat equal to c, then the heat, Q, required to raise the temperature of that object by an amount AT is Q = m C(AT). A latent heat L expresses the amount of energy in the form of heat Q (released or absorbed by a body or a thermodynamic system during a constant-temperature process) required to completely effect a phase change of a unit of mass m, of a substance: Q = m L, where Q is the amount of energy released or absorbed during the change of phase of the substance, m is the mass of the substance, and L is the specic latent heat for a particular substance, either Lf for fusion (melting or freezing), or L 1, for vaporization (boiling or condensing). pressure Phase diagrams plot pressure versus temperature, and show conditions (pressure, temperature) at which thermodynamically distinct phases (such as solid, liquid or gaseous states) occur and coexist at equilibrium. The lines represent the combinations of pressures and temperatures at which two phases can exist in equilibrium. Triple point is the point on a phase diagram at which the three states of matter (gas, liquid, and 1 temperature solid) coexist, and the critical point is the point on a phase diagram at which the substance is indistinguishable between liquid and gaseous states. Activity 1: Specic Heat Capacity Open the Energy Forms and Changes simulation. Choose the Intro tab. Play around to become comfortable with the sim. 1. Attach the temperature gauge to each object (brick, iron, and water) so you have a temperature guide. Which object (brick, iron, and water) is at the higher temperature? 2. Which object (brick, iron, and water) contains more energy? To answer this question make sure the energy symbols box is checked. 3. Reset the sim. Place the water beaker on the stand. Chill the water as much as possible, then add heat and observe. List below at least three observations (make sure the energy symbols box is checked.) 4. Reset the sim. Heat the iron block to the maximum temperature. Place the heated-up iron block in the water container at room temperature. Describe what happens with the temperature and energy stored by each object. 5. Reset the sim. Cool the iron block to the minimum temperature. Place the cooled-down iron block in the water container at room temperature. Describe what happens with the temperature and energy stored by each object. 6. Reset the sim. Place the brick on top of the iron block and add heat. Describe what happens with the temperature and energy stored by each object. 7. Once the brick and the iron cooled down, do they have the same thermal energy? Do they have the same temperature? 8. Place the brick on top of the iron block and place them in the beaker. Add heat to the system. Once it reached the maximum temperature, place the brick and the iron blocks on the table. Based on your observations, rank in order from most to least, the material that can hold the most heat. 9. Based on your observations, rank in order from largest to shortest time, the material that take the longest to cool down. 10. How does heat ow from one substance to another? What evidence did you experience to justify this answer? Activity 2: States of Matter This activity allows the study of the characteristics of the three states of matter (solid, liquid, and gas) for neon, argon, oxygen, and water. 11. Open the States of Matter PhET simulation. Choose the States tab. Play around to become comfortable with the sim. 12. Use the sirn to explore the behavior of neon atoms in the solid, liquid, and gaseous states, by using the menu on the right side of the window to select the state. Make observations on the shape, volume, and motion of particles in each state, and record your observations in the Table 1 below. Table 1: Neon Characteristics State solid liquid gas temperature __ volume changes in particle speed when heat is added to container changes in particle speed when heat is removed from container changes in the distance between particles when heat is added to container changes in the distance between particles when heat is removed om container 13. For each of the three states, use the slider on the bottom of the program to Add Heat. Notice the change in temperature as register by the thermometer at the top of the program. Does the particle speed change when heat is added to the container? Record your observations in Table 1. 14. For each of the three states, how does the distance between the particles change when heat is added to the container? Record your observations in Table 1. 15. For each of the three states, use the slider to Remove Heat. Does the particle speed change when heat is removed from the container? Record your observation in Table 1. 16. For each of the three states, how does the distance between the particles change when heat is removed from the container? Record your observations in Table l. 17. Use the sim to explore the behavior of argon atoms in the solid, liquid, and gaseous states. Repeat the previous steps, and record your observations in the Table 2 below. Table 2: Argon changes in particle speed when heat is added to container changes in particle speed when heat is removed from container changes in the distance between particles when heat is added to container changes in the distance between particles when heat is removed from container 18. How does argon atoms\" behavior compare with the neon atoms' behavior? 19. Based on your observations so far, for the gure below showing oxygen in three different states: solid, liquid, and gas, predict which picture (left, middle, or right) best describes oxygen gas. 20. Run the sim for oxygen. Was your prediction correct? 21. Based on your observations so far, for the gure below showing water in three different states: solid, liquid, and gas, predict which picture (left, middle, or right) best describes liquid water? 22. Use the sim to explore the solid, liquid, and gaseous states of water. Was your prediction correct? 23. What unusual property of water makes it different from the other liquids? (Hint: think about why do we worry about water freezing in pipes during winter). Activity 3: Phase Changes In the States of Matter PhET simulation, choose the Phase Change tab. The sim has a similar layout as the previous one, but offers the ability to add particles into the container by using the pump, allows the measurement of pressure, and allows the user to vary the volume of the container. The user also has the ability to adjust the interactions between the atoms or molecules of the gas, and can watch the corresponding phase diagram. The simulation allows the study of neon, argon, oxygen, and water. Play around to become comfortable with the sim. 24. Reset the sim. Use the sim to explore the behavior of water atoms. In addition to adding and removing energy to/om the system, you can move the container's lid and use the phase diagram to understand what phase the substance is in. In what state is the water when you reset the sim? How do you know? 25. How does a change in temperature affect the pressure inside the container? 26. Look at the Phase Diagram. What happens to the red dot as you add heat? What happens to the red dot as you remove heat? 27. Using the simulation, describe 3 different ways to achieve a change in state of matter of a substance: 28. Reset the sim and choose the adjustable attraction. Use the slider to vary the strength of the interaction between particles. Compare the behavior of particles with strong interaction to those having a weak interaction making note of the temperature and the state of matter of the substance in the container. 29. Describe the relationship between the interaction change and the temperature at which the water undergoes a phase change. 30. Based on the Phase Diagram, what is the melting/freezing point of water in Kelvin? What is the boiling/condensation point of water in Kelvin? (Hint: The temperatures given when you click solid, liquid, and gas are NOT the melting and boiling points.) List the temperatures in the Table 3 below. Table 3: substance Triple Point Critical Point Temperature (K) Temperature (K) water oxygen 31. Repeat the procedure for the substances other than water from the menu on the right side of the sim