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Understanding Phase Changes

Explore how altitude affects water’s freezing, melting, and boiling points. Learn why cooking changes at high elevations and how pressure cookers help speed up cooking under high pressure.

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    Name: Julieta Aguilar Date: 3/21/23 Student Exploration: Phase Changes Vocabulary: altitude, boil, boiling point, freeze, freezing point, gas, liquid, melt, melting point, phase, solid Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. A family from Minnesota turns off the heat and flies to Florida for a winter holiday. When they come home, all of their water pipes have burst. What do you think happened? The water pipes froze, meaning the water expanded and the pipes burst. 2. Spaghetti takes about 9 minutes to cook at sea level, but about 14 minutes in the mountains. Why do you think this is so? As attitude increasesand atmosphere pressure decrease, the boiling point of water decreases. Gizmo Warm-up In the Phase Changes Gizmo, select Micro view and set the Ice volumeto 50 cm 3 . Notice the nitrogen {%), oxygen {$), and water {<') molecules. Click Flay { ► ) and observe water molecules in the solid (ice), liquid (water), and gas {air) phases. 1. In which phase(s) are the molecules held rigidly together? Solid - Ice 2. In which phasefs) do the molecules move freely? Gas 3. In which phase(s) are the molecules held in a defined shape? Solid - Ice 4, In which phase(s) do the molecules take the shape of their container? Liquid and Gas ■ ' 2019 I >i - 1i-.il UH I M' ■ :• II-. rr -,rl vr‘11

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    Get the Gizmojeady : i Activity A: * Click Reset ( ) and select Macro view. Phase changes * Set the Water temperature to 10 “C. • Set the Ice volume to 0 cm s . _____k ________ Question: How i s temperature related to phase changes? 1. Presict: Based on your prior knowledge, predict the following: A. At what temperature will water change from a liquid to a solid (freeze)? 0 degrees C B. At what temperature will water change from a solid to a liquid (melt)? 55 degrees C C. At what temperature will water change from a liquid to a gas (boil)? ICO degrees C 2. Investigate: Use the Gizmo to explore phase changes. Use the Add/remove heat energy slider to control the water temperature. Record your observations in your notes, then answer the questions below: A. At what temperature does water freeze 0 degrees C This is the freezing point. B. At what temperature does ice melt? 0 degrees C This is the melting point C. At what temperature does water boil? 100 degrees C This is the boiling point 3. Observe: Set up the Gizmo to observe freezing. What do you notice about the temperature while the water is in the process of freezing? Temperature goes down 4. Explore: Use the Gizmo to investigate melting and boiling. Does the temperature change while either of these phase changes is occurring? The temperature goes up 5. Interpret Select the GRAPH tab to see a graph of temperature vs. time. Click the " button until the whole graph i s visible. What does the graph look like during a phase change? As it gets hotter it exponentially goes up. 6. Extend your thinking: Why do you think the temperature does not change much during a phase change? If possible, discuss your answer with your classmates and teacher. Since the energy involved in a phase change is used to break bonds, there is no increases in the kinetic energies of the particles, and therefore no rise in temperature. 1 ) 2 0 1 9 l >| H r-,i|r-i||i / A l l i ; ■ I •, rV’ir'l U f l '

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