# HEAT ENERGY AND TEMPERATURE

Heat energy is transferred from one body to another due to temperature differences. If two bodies of different temperatures are brought together, the energy will be transferred from the hotter body to the colder body, that is, the heat flow. The effect of this energy transfer is usually but not always, that the temperature of the colder body increases, and the temperature of the hotter body decreases.

## CONTENT

CONCEPT OF HEAT AND TEMPERATURE

EFFECTS OF HEAT

KINETIC MOLECULE THEORY

MEASUREMENT OF TEMPERATURE

TEMPERATURE SCALES

THERMOMETRIC CALCULATIONS

PROPERTIES AND IMPORTANCE

#### CONCEPT OF HEAT AND TEMPERATURE

Matter can be transformed from one physical state (or phase) to another physical state (or phase), such as from solid to liquid (melting), from solid to steam (sublimation), from liquid to steam (boiling), or from one solid form to another. The 18th and 19th centuries clarified the important difference between heat and temperature (heat is a form of energy, temperature is a measure of the amount of energy present in the body).

### EFFECTS OF HEAT ENERGY

The important effects of heat on an object are listed below:

1. Raises the temperature.
2. Increases volume.
3. Changes state
4. Brings about chemical action.
5. Changes physical properties.

#### KINETIC MOLECULE THEORY

1. Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion.
2. These particles move in a straight line until they collide with another particle or the walls of the container.
3. These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.
4. There is no force of attraction between gas particles or between the particles and the walls of the container.
5. Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container.
6. The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.

#### MEASUREMENT OF TEMPERATURE

Temperature is the amount measured by the thermometer. Temperature is related to the average kinetic energy of atoms and molecules in the system. Absolute zero is the temperature at which there is no molecular movement. There are three main temperature scales: Celsius, Fahrenheit and Kelvin.

1.  Temperature Scales

Celsius or centigrade: is the scale and unit of measurement of temperature. It is one of the most commonly used temperature units. Degrees Celsius, also known as degrees Celsius, is the scale for measuring temperature. The unit of measurement is Celsius (°C). It is one of the most commonly used temperature units in the world.

Fahrenheit scale: In this scale, the freezing of water is defined as 32 degrees,and the boiling point of water is defined as 212 degrees. Fahrenheit scale measures temperature. It is based on the scale proposed by physicist Daniel Gabriel Fahrenheit (1686-1736) in 1724. The unit of this scale is Fahrenheit (°F). On this scale, the freezing point of water is defined as 32 degrees, and the boiling point of water is defined as 212 degrees.

Absolute zero: is the coldest possible temperature;officially,it is the temperature at which entropy reaches its minimum. Absolute zero is the coldest temperature. Formally,it is the temperature at which entropy reaches its minimum value. More simply, absolute zero refers to the state in which all the energy of the system is extracted (by definition, the lowest energy state the system can have). Absolute zero is universal in the sense that all substances are in the ground state at this temperature. Therefore, as the zero point of the temperature unit system is a natural choice.

Kelvin: is the unit of measurement of temperature. The zero point of the Kelvin scale is absolute zero, the lowest possible temperature. Kelvin is the unit of measurement of temperature. It is one of the seven basic units in the International System of Units (SI) and is assigned the unit symbol K. The Kelvin scale is absolute, and the thermodynamic temperature scale uses absolute zero as its zero point. In the classical description of thermodynamics, absolute zero is the temperature at which all thermal motion stops

2. Thermometric conversions

1. To convert from Fahrenheit (of) to Celsius (0C) use

oC = 5 (oF-32)

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• To convert from degree centigrade (oC) to degree Fahrenheit (oF)

Uses    of = 9oC + 32 or oF = 1.8oC + 32

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3. Thermometric Properties

Definition of temperature measurement properties: The properties of objects that change with temperature are called temperature measurement properties. The device used to measure temperature is called a thermometer.

Different thermometer properties and thermometers are given below

* Temperature measurement characteristics of fixed capacity gas thermometer.

* Resistance metal.

* Mercury columns in capillaries.

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