key term - Coffee cup calorimeter

Definition

A coffee cup calorimeter is a simple device used to measure the heat change associated with chemical reactions or physical changes. It typically consists of two Styrofoam cups nested together to minimize heat exchange with the environment, and is equipped with a thermometer to monitor temperature changes during the reaction. This tool is particularly useful in thermochemistry to determine specific heat and heats of reaction in a controlled setting.

5 Must Know Facts For Your Next Test

1. The coffee cup calorimeter operates under constant pressure, making it ideal for measuring heats of reaction in solution.
2. It is commonly used in classrooms due to its simplicity and low cost, allowing students to easily conduct experiments.
3. The temperature change measured in a coffee cup calorimeter can be used to calculate the enthalpy change using the formula: $$q = m imes c imes riangle T$$, where 'q' is the heat absorbed or released, 'm' is mass, 'c' is specific heat capacity, and $$ riangle T$$ is the change in temperature.
4. Because it is an open system, the coffee cup calorimeter can also be affected by evaporation, which may need to be considered in more precise experiments.
5. The heat capacity of the entire calorimeter setup must be accounted for when calculating heat changes in reactions taking place inside it.

Review Questions

• How does a coffee cup calorimeter function to measure heat changes in reactions?
  • A coffee cup calorimeter functions by isolating the reaction mixture within two nested Styrofoam cups to minimize heat exchange with the surrounding environment. The thermometer inside measures the temperature change of the solution before and after the reaction occurs. By knowing the specific heat capacity of the solution and its mass, you can apply the formula $$q = m \times c \times \triangle T$$ to calculate the heat absorbed or released during the reaction.
• What are some potential sources of error when using a coffee cup calorimeter, and how might these affect results?
  • Some potential sources of error when using a coffee cup calorimeter include heat loss to the environment, incomplete mixing of reactants, and evaporation of volatile components. If heat is lost to the surroundings, it could lead to an underestimation of the heat change during the reaction. Similarly, if all reactants do not fully interact or if some evaporate, it could skew results by either decreasing reactant amounts or altering concentrations, resulting in inaccurate enthalpy calculations.
• Evaluate how the design and setup of a coffee cup calorimeter can influence the accuracy of thermochemical measurements.
  • The design and setup of a coffee cup calorimeter significantly influence measurement accuracy through factors like insulation quality and containment structure. The choice of materials, such as using Styrofoam for effective insulation, minimizes thermal exchange with ambient conditions. Additionally, ensuring that reactants are thoroughly mixed within a closed environment reduces potential discrepancies from external factors like evaporation or atmospheric pressure variations. Overall, careful consideration in design directly correlates with achieving precise thermochemical data.

Related terms

enthalpy: A thermodynamic quantity representing the total heat content of a system, often used to describe the heat changes during chemical reactions.

specific heat capacity: The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius, essential for understanding heat transfer in calorimetry.

thermochemical equation: An equation that shows the relationship between the quantities of reactants and products in a chemical reaction along with the enthalpy change.