ANS:C - specific heat

The heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapor by 1°F is called sensible heat. Explanation:

1. Sensible Heat:
   • Sensible heat refers to the heat exchange associated with changes in temperature of a substance without a change in phase (i.e., without a change between solid, liquid, or gas phases).
   • When the temperature of a substance changes, sensible heat is transferred to or from the substance, causing its temperature to rise or fall.
   • In the context of gas and vapor mixtures, sensible heat represents the heat required to increase or decrease the temperature of the mixture without changing its phase (i.e., without condensing or vaporizing any of the components).
2. Latent Heat:
   • Latent heat, on the other hand, refers to the heat exchange associated with phase changes (i.e., changes between solid, liquid, and gas phases) at constant temperature.
   • When a substance undergoes a phase change, latent heat is absorbed or released, causing the substance to change phase while its temperature remains constant.
   • For example, in the case of water, latent heat is absorbed during vaporization (changing from liquid to vapor) and released during condensation (changing from vapor to liquid) at a constant temperature.
3. Humid Heat:
   • Humid heat is a term less commonly used and may refer to the specific heat or heat capacity of a moist or humid air mixture.
   • It describes the amount of heat required to raise the temperature of a unit mass of moist air by 1°C or 1°F.
4. Specific Heat:
   • Specific heat is the amount of heat required to raise the temperature of a unit mass of a substance by 1°C or 1°F.
   • It is a property of the substance and is typically expressed in units of energy per unit mass per unit temperature (e.g., BTU/lb°F for English units).