Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

In the heat of combustion equation, what variable is represented by 'q'?

1. The change in temperature

2. The heat added or removed

3. The total energy in a system

4. The pressure applied

The correct answer is: The heat added or removed

In the context of the heat of combustion equation, 'q' represents the heat added or removed from a system during a chemical reaction, specifically a combustion reaction. This variable quantifies the energy change that occurs when a substance combusts, typically measured in joules or calories. Combustion reactions release energy in the form of heat when fuels react with oxygen, leading to a temperature increase in their surroundings. Thus, 'q' accounts for the total amount of heat energy involved in this process, reflecting either the energy released (exothermic reaction) or absorbed in other contexts. This is essential for understanding thermodynamics and energy transfer in chemical processes. The other potential variables listed do not accurately represent what 'q' signifies in this scenario. The change in temperature relates to the result of an energy change, not the energy itself, while total energy in a system encompasses all forms of energy and does not specifically denote heat transfer. Pressure is a separate parameter that can affect reactions but does not define the heat energy change directly.