Lesson Objective: Phase changes can occur as a result of changes in the temperature of a substance. To make ice cream, the ingredients need to be cold enough to freeze.
Materials Needed
Prep
What are scholars doing in this lesson?
Do Now
Launch
Experiment
[Engagement Tip: Allow scholars to pour the contents of their failed experiment into a cup and enjoy a “milkshake” as they reflect on their work.]
Discourse Debrief experiment:
Introduce the Essential Question:
Accountability (Lab Notebook)
Scoring
Lesson Objective: Molecular motion is always present in solids, liquids, and gases. Heating and cooling change the speed and position of the molecules that make up a substance. Temperature is a measure of the average kinetic energy of particles, and temperature is not a form of energy. Scholars must be able to make connections between phase changes, energy, and intermolecular distance. Increased energy causes the molecules in a substance to spread, whereas lowered energy causes them to condense. When particles spread or condense, a phase change can occur. Substances have different properties after a phase change.
Materials Needed
Prep
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Do Now
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Activity Adapted from Terry Bollinger’s 2013 essay on molecules, “A Dance of Molecules”
[Tip: Guard against the misconception that molecular movement stops in a solid.]
Discourse Debrief activity:
Make broader connections:
Make connections to the Essential Question:
Accountability (Lab Notebook)
Scoring Award points as follows:
Do Now
Launch
Activity
Discourse Debrief activity:
Make connections to the Essential Question:
Accountability (Exit Ticket) Todd wants to know what happens to water molecules as they undergo phase changes.
Image Credit: ertunc , Public domain, via Wikiversity
Todd also wonders about the difference between temperature and thermal energy.
Scoring Award points as follows:
Lesson Objective: Substances at different temperatures often come into contact, which results in thermal energy flowing from the warmer substance to the cooler one in an attempt to reach thermal equilibrium. Endothermic processes are accompanied by or require the absorption of heat (heating), while exothermic processes are accompanied by the release of heat (cooling).
Materials Needed
Prep
What are scholars doing in this lesson?
Do Now
Launch
Experiment
Discourse Debrief experiment:
Make connections to the Essential Question:
Accountability (Exit Ticket) After attending his cousin’s birthday party in his backyard, Michael forgot his balloon outside when he went to bed. Overnight, the temperature dropped significantly. When Michael saw the same balloon the next morning, it looked different.
Scoring Award points as follows:
Lesson Objective: Various substances undergo phase changes at different temperatures. Scholars understand that the ice cream ingredients didn’t freeze on the first day of the unit because they didn’t cool enough to reach their freezing points! They will not know that the boiling or freezing point of a substance can actually change based on environmental conditions. They can better differentiate between evaporation and boiling.
Materials Needed
Prep
What are scholars doing in this lesson?
Do Now
Launch
Experiment
Discourse Debrief experiment:
Make connections to the Essential Question:
Make broader connections:
Accountability (Exit Ticket) Two substances are cooled in separate beakers. After 10 minutes of cooling, both substances have a temperature of 5°C. At this temperature, one substance is a liquid and the other is a solid. Use the information provided to answer the questions that follow:
Scoring Award points as follows:
Lesson Objective: The temperature of a substance remains the same as it undergoes a phase change due to kinetic energy staying the same (only potential energy is changing). Heating and cooling curves show the slopes and plateaus that occur as the temperature of a substance changes over time, with a positive slope indicative of heating and a negative slope indicative of cooling. A plateau on a heating curve occurs because the energy being taken in is used to overcome intermolecular forces. A plateau on a cooling curve occurs because while potential energy is released as molecules condense, kinetic energy does not begin to change again until the phase change is complete.
Materials Needed
Prep
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Image Credit: Adapted from Community College Consortium for Bioscience Credentials, CC BY 3.0, via Wikimedia Commons
Activity
[Tip: Scholars may be familiar with drawing a line of best fit on a graph. Explain to scholars why they should avoid this when creating heating/cooling curves.]
Discourse Debrief activity:
Make connections to the Essential Question:
Accountability (Exit Ticket) The image below shows the cooling curve for a substance.
1.I
2.II
3.III
4.I and II
Scoring Award points as follows:
Lesson Objective: The addition of another substance can elevate (increase) or depress (decrease) the boiling point of a substance.
Materials Needed
Prep
What are scholars doing in this lesson?
Do Now
Launch
Experiment
[Tip: To avoid running out of time, assign each group one of the three types of water. Allow the class to share data.]
[Tip: Allow scholars to use colored pencils to highlight the three lines on their graph.]
Discourse Debrief experiment:
[Tip: Scholars may be surprised to learn that the salt water actually takes longer to boil than the plain water. It is a common myth that it makes the water boil faster. So why do so many people believe it? This is a good topic to explore further if time allows. Note: While salt raises the boiling point of water, salt does not interact with all substances in the same way that it interacts with water.]
Make connections to the Essential Question:
Accountability (Exit Ticket) Shayne conducted an experiment to determine whether hand sanitizer or water had a lower boiling point. He collected the data in the table below.
Time on hotplate |
0 min 1 min 2 min 3 min 4 min 5 min 6 min 7 min 8 min |
Temperature of hand sanitizer |
19°C 36°C 55°C 75°C 75°C 75°C 92°C 106°C 120°C |
Temperature of water |
19°C 34°C 48°C 61°C 74°C 87°C 100°C 100°C 100°C |
Exemplar:
Scoring Award points as follows:
Lesson Objective: The addition of another substance can elevate (increase) or depress (decrease) the melting or freezing point of a substance. Salt depresses the freezing point of water.
Materials Needed
Prep
What are scholars doing in this lesson?
Do Now
Launch
Experiment
[Classroom Management Tip: As scholars are waiting for the ice to melt, give them something else to work on (such as a related article to read, an online simulation to complete, or Exit Ticket feedback to review).]
Discourse Debrief experiment:
Make broader connections:
Make connections to the Essential Question:
Accountability (Exit Ticket) During the winter, Khari takes a walk on a beach with his family. He is surprised to see that the ocean water isn’t frozen. He takes the temperature of the water, and discovers that it is −2°C! He knows that the freezing point of water is 0°C, so he doesn’t understand how it is possible that the ocean water is both −2°C and still a liquid.
He asks his siblings what they think, and they reply with the following ideas:
Tabia’s statement is most accurate. Khari doesn’t know it, but what he is observing in the water is called freezing point depression. The salt in the ocean is mixing with the water and causing the freezing point to lower, so even though the water is colder than 0°C, it is able to remain a liquid.
Scoring Award points as follows:
Lesson Objective: Intermolecular forces and atmospheric pressure affect the temperature at which a phase change occurs. The boiling point of a liquid depends on the intermolecular forces present between the molecules in the liquid, because you must disrupt those forces to change it from a liquid to a gas. Lowering atmospheric pressure will lower the boiling point of a liquid. This is due to the fact that the vapor pressure of water depends upon temperature.
Materials Needed
Prep
What are scholars doing in this lesson?
Do Now
Launch
Experiment
Discourse Debrief experiment:
[Tip: Understanding atmospheric pressure and vapor pressure as well as their effects on matter will likely be tricky for scholars. They also may find it difficult to believe that atmospheric pressure exists because they don’t “feel it.” Consider revisiting these concepts on another day to give scholars more practice and familiarity with them.]
Make connections to the Essential Question:
Make broader connections:
Accountability (Exit Ticket)
1.Tyla begins heating 200 mL samples of two different substances at the same time. She notices that they begin to boil at different times. If she heats them both under identical conditions, why might one substance boil before the other? Use your knowledge of intermolecular forces and energy in your response. [4]
The two substances are different and thus have different intermolecular forces. Substances with stronger attractive intermolecular forces have molecules that are harder to separate. Because of this, more energy is required to physically spread the molecules apart.
Tyla lives in Denver, Colorado, while her friend Esther lives in Philadelphia, Pennsylvania. They each heated 200 mL of Substance A in their respective cities, and noticed a 5 degree difference in the substance’s boiling point. The table shows some facts for each city on the day they heated Substance A.
Location | OutsideTemperature | (℉ Elevation(ft. above sea level) | Weather | Time |
---|---|---|---|---|
Philadelphia, PA |
56 |
39 |
Windy |
12 PM |
Denver, CO |
50 |
5300 |
Calm |
10:15 AM |
2.Which is the best explanation for the difference in boiling points? [1]
Scoring Award points as follows:
Lesson Objective: Multiple factors influence the state of a substance. A mixture of ice and salt has a lower temperature than their ice by itself, allowing the liquid ice cream ingredients to freeze when they are exposed to the cold brine! Materials Needed
[Tip: Scholars who cannot eat ice cream can use a partially frozen or unfrozen freeze pop in place of the milk/cream/sugar mixture.]
Prep
What are scholars doing in this lesson?
Do Now
Launch
[Tip: Show scholars some of the additional materials that are available, including salt and sugar.]
Activity
[Engagement Tip: If many groups are having a hard time, stop the class and allow a group that has a strong plan to share their ideas and reasoning with their peers.]
Discourse Debrief activity:
Accountability (Lab Notebook)
Scoring Award points as follows:
Do Now
Launch
Experiment
[Materials Management Tip: Leave ample time for cleanup after this investigation!]
Discourse Debrief experiment:
Make connections to the Essential Question:
Accountability (Exit Ticket)
Today was successful due to the effective revisions my group made to the original procedure. On the first day of the unit, our ingredients melted. This time, the ice was kept on the outside of the bag and combined with salt to depress (lower) its melting point. This enabled the ice to draw more energy from the ingredients in the inner resealable plastic bag, lowering their temperature and ultimately causing them to freeze.
Scoring Award points as follows:
Vocabulary List
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