Worked example: Measuring the energy content of foods using soda-can calorimetry | Khan Academy | Summary and Q&A

TL;DR

By using a soda can calorimeter, a marshmallow is burned to find its energy content, revealing that it contains approximately three calories per gram.

Key Insights

• 🥵 Calorimetry is a method used to measure heat flow and determine the energy content of substances.
• 🥵 Using a soda can calorimeter setup, the heat given off by burning a marshmallow is transferred to the water in the soda can.
• 🥵 The heat gained by the water can be calculated using the specific heat equation.
• 🥵 The positive sign in the heat gained by the water indicates that heat was gained, resulting in an increase in temperature.
• 🥵 The heat given off by the burning marshmallow is not equal to the heat gained by the water due to the imperfect transfer of heat.
• ❓ The soda can calorimeter setup used in this experiment is an example of constant pressure calorimetry.
• 🥵 The heat transferred under constant pressure is the definition of the change in enthalpy, represented as delta H.

Transcript

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Questions & Answers

Q: What is calorimetry?

Calorimetry refers to the measurement of heat flow. In this experiment, it is used to determine the energy content of a marshmallow.

Q: How does the soda can calorimeter setup work?

The soda can contains water and a thermometer to measure the change in temperature. The marshmallow is burned on a pin attached to a piece of cork, and the heat given off by the burning marshmallow is transferred to the water in the soda can.

Q: What does the positive sign in the heat gained by the water indicate?

The positive sign means that heat was gained by the water, resulting in an increase in temperature. This indicates that the burning of the marshmallow released energy.

Q: Why is the heat given off by the burning marshmallow not equal to the heat gained by the water?

The heat given off by the burning marshmallow is not equal to the heat gained by the water because there is no perfect transfer of heat. Some heat could have been lost to the environment, preventing all of it from being transferred to the soda can.

Summary & Key Takeaways

• Calorimetry refers to the measurement of heat flow, and in this experiment, a marshmallow is burned to determine its energy content.

• By using a soda can calorimeter setup with water, a thermometer, and a marshmallow on fire, the heat given off by the burning marshmallow is transferred to the water in the soda can, resulting in an increase in temperature.

• The heat gained by the water can be calculated using the specific heat equation, and assuming a perfect transfer of heat, the magnitude of heat gained by the water should be equal to the heat given off by the burning marshmallow.