Physical Science - Questions About Phase Change Lab - With Solutions PDF

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Phase change lab questions Period: Physical Science

Name: Date:

Pre-lab: (As always, write in complete sentences) 1. What should happen to the temperature of a substance while the substance is melting? Why is that?

The temperature should remain the same because all of the energy is going to change the substance from a solid to a liquid rather than changing the temperature 2. If a substance melts at 25 °C, at what temperature should it freeze and why?

The substance should freeze at 25 °C because the change from a liquid to a solid (freezing) is just the opposite of changing from a solid to a liquid (melting) so they should occur at the same temperature. 3. For the following cases, explain whether it is gaining or losing energy? Use kinetic theory of matter in your explanation. a) While melting

While an object is melting it is gaining energy because it must take in energy (endothermic) to change from a solid to a liquid because the molecules must go from just vibrating to flowing around more. b) While freezing

While an object is freezing it is losing energy because freezing is exothermic, so liquids give off energy to become solids because the molecules go from moving around more to just vibrating in place.

Temperature

4. Draw what the temperature vs. time graph (no numbers needed) should look like for a solid that is heated to a liquid that is a few degrees above the melting point, and then the material is removed from the heat an allowed to solidify again and is cooled to a few degrees below the melting point. Label where the substance will be: 1) solid, or liquid, 2) where the substance is melting or freezing, and 3) where the object is taking in or giving off energy. Note some of these can occur simultaneously (so it could be cooling and a liquid for example)

Melting & taking in energy

Liquid & giving off energy

Freezing & giving off energy Liquid & taking Solid & giving in energy off energy Solid & taking in energy Time

5. Explain why you drew the graph you did from number 4.

The temperature rises as the solid is heated, but stays the same during a phase change to liquid. The temperature rises again when the substance is heated. Once the heat is removed, the substance starts releasing energy, lowering temperature, leveling off during the freezing, and then dropping again as the solid cools. Data and Results: Conduct the lab as described in the instructions. Your Data will be the table below and your Capstone graph. Once you’ve collected data as described in the instructions do the following: 

Using the Annotation tool (the A), do the following:

      

Your names, period and date Where the substance is a solid and heating Where the substance is melting, listing the approximate melting point Where the substance is a liquid and heating Where the substance is a liquid and cooling Where the substance is freezing, listing the approximate freezing point Where the substance is a solid and is cooling.



Using the coordinates tool record the following:

Item

Temp °C

Starting temperature of the solid

43°C...