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.

Short answer

The process of liquid water turning to ice is an exothermic process. As water freezes, its molecules slow down, forming a rigid structure, which requires releasing heat to the surroundings. The system's potential energy increases due to the more stable arrangement in the ice, while its kinetic energy decreases as the molecules move slower. This results in a decrease in the overall energy of the system and heat transfer to the surroundings.

Step-by-step solution

Identify endothermic and exothermic processes

An endothermic process is a process that absorbs heat from the surroundings, leading to an increase in the internal energy of the system (liquid water in this case). On the other hand, an exothermic process is a process that releases heat to the surroundings, leading to a decrease in the internal energy of the system (liquid water turning to ice).

Describe the system and surroundings

In this case, the system is the liquid water, and the surroundings are the environment around the liquid water. During the process, liquid water transforms into ice, with heat being exchanged between the system and surroundings.

Understand the process of liquid water turning to ice

When liquid water turns to ice, it undergoes a phase change called freezing. During this phase change, water molecules slow down and form a rigid structure. This process requires a release of heat energy from the system (liquid water) to the surroundings.

Analyze potential and kinetic energy changes

During the freezing process, the potential energy of water molecules increases because of the formation of a more stable and structured arrangement in the ice. Simultaneously, the kinetic energy of water molecules decreases since they are moving slower due to the lower energy state. As a result, the overall energy of the system decreases.

Determine if the process is endothermic or exothermic and explain using the given terms

Since freezing involves releasing heat to the surroundings and a decrease in the overall energy of the system (from a decrease in kinetic energy), the process of liquid water turning to ice is an exothermic process.