Question

A student making a coffee cup calorimeter fails to use a second coffee cup and inadequately seals the lid. What was her initial goal, and what was the result of this mistake? a. She was trying to create an isolated system but created an open system instead. b. She was trying to create an isolated system but created a closed system instead. c. She was trying to create a closed system but created an open system instead. d. She was trying to create a closed system but created an isolated system instead.

Short answer

a. She was trying to create an isolated system but created an open system instead.

Step-by-step solution

Understand the goal of a coffee cup calorimeter

A coffee cup calorimeter is used to measure the change in temperature during a chemical reaction. The goal is to create an isolated system to prevent exchange of matter and energy with the surroundings.

Define isolated, closed, and open systems

An isolated system does not exchange matter or energy with its surroundings. A closed system exchanges energy but not matter. An open system exchanges both matter and energy.

Analyze the mistake made by the student

The student failed to use a second coffee cup and inadequately sealed the lid, thereby allowing the exchange of matter and energy with the surroundings, which is characteristic of an open system.

Match the analysis to the correct answer

Based on the analysis, the student's initial goal was to create an isolated system but created an open system instead.

Select the correct option

The correct answer is given by option (a): She was trying to create an isolated system but created an open system instead.

Key concepts

Isolated System

In thermodynamics, an isolated system is one where neither matter nor energy can be exchanged with the surroundings. This means there's no heat transfer, no mass moving in or out, and the system remains completely insulated from external influences.
An example of an isolated system would be a perfectly insulated thermos flask where no heat escapes, and nothing enters or leaves the container.

In the context of the coffee cup calorimeter exercise, the student's goal was to create an isolated system. This was supposed to prevent any heat exchange or matter exchange with the environment, maintaining constant internal conditions for accurate measurement of the chemical reaction's temperature change. To achieve this, careful sealing and insulation are crucial. Without a proper second coffee cup or a tightly sealed lid, the isolation can be compromised, as evidenced by the student's mistake.

Closed System

A closed system in thermodynamics allows the exchange of energy (such as heat or work) but does not permit the exchange of matter with its surroundings. This means while energy can be transferred into or out of the system, the contents (matter) of the system remain fixed.

For example, a saucepan with a lid on a stove can be considered a closed system when cooking soup. Heat can transfer from the stove to the pot and into the soup, but the steam (matter) cannot escape if the lid is properly sealed.

In our exercise concerning the coffee cup calorimeter, the student did not achieve even a closed system. Her failure to properly seal the lid and use a second coffee cup meant not just energy but also matter (like water vapor) could escape or enter. Hence, the system behaved more like an open system rather than a closed one.

Open System

An open system is one that exchanges both matter and energy with its surroundings. Many systems in our everyday life are open systems. This is the most common type of system seen in practical applications.

For instance:

• A boiling pot with no lid
• A running engine in a car
• A living organism, such as a human

These systems constantly exchange energy and matter with their surrounding environments.

In the coffee cup calorimeter exercise, failing to use a second cup and improper sealing led to an open system. Here, both energy (through heat) and matter (through water vapor or gases) could freely move in and out. Consequently, the measurements taken would be inaccurate, illustrating the critical importance of correctly creating an isolated system for precise calorimetry.