Problem 4 - Chemistry An Atoms First Approach

Question

Liquid water turns to ice. Is this process endothermic or exothermic? Explain what is occurring using the terms system, surroundings, heat, potential energy, and kinetic energy in the discussion.

Step-by-Step Solution

Answer

The process of liquid water turning into ice is an exothermic process, as heat is released to the surroundings. In this process, the system (liquid water) loses kinetic energy as it cools, which results in the water molecules coming closer together, forming a solid structure and increasing potential energy. The decrease in kinetic energy leads to a release of heat energy into the surroundings.

Step 1: Definition of Endothermic and Exothermic Processes

Endothermic processes absorb heat from the surroundings, causing a decrease in the temperature of the surroundings. In contrast, exothermic processes release heat to the surroundings, causing an increase in the temperature of the surroundings.

Step 2: Define the System and Surroundings

In this scenario, the system is the liquid water turning into ice. The surroundings include everything outside the system, such as the container holding the water and the air around it.

Step 3: Understanding Heat, Potential Energy, and Kinetic Energy

Heat is the transfer of thermal energy between two objects due to a temperature difference. Potential energy is the stored energy in an object due to its position or state. Kinetic energy is the energy possessed by an object due to its motion.

Step 4: Analyzing the Process of Liquid Water Turning into Ice

When liquid water turns into ice, the temperature of the system decreases as it reaches the freezing point (0°C or 32°F). In this process, the water molecules slow down and lose kinetic energy as they cool. The decrease in kinetic energy results in molecules coming closer together and forming a solid structure, leading to an increase in potential energy.

Step 5: Determining if the Process is Endothermic or Exothermic

As the liquid water turns into ice and loses kinetic energy, heat is released to the surroundings. This transfer of heat energy indicates an exothermic process. Therefore, the process of liquid water turning into ice is an exothermic process.