What is Thermodynamics?
Thermodynamics is the part of physics that deals with the relation between heat and other forms of energy. In particular, it explains how thermal energy converted to and from different types of energy and how it aﬀects matter.
Thermodynamics is involved with different properties of matter; first among these is heat.
1. Heat is energy transferred between substances or systems due to the difference in temperature.
As a form of energy, heat is conserved; i.e., it cannot be created or destroyed. It can, however, transferred from one place to another. Heat converts to and from other forms of energy. Not only does energy change form, but matter (that is, material or substance) also changes form in many thermodynamic systems.
Water evaporating into the air forms storm clouds. As the water vapor reaches the colder parts of the atmosphere, it condenses to form clouds. Eventually, the amount of moisture the clouds contains enough to collect into droplets and form liquid water again, so it rains.
2. One thing people have observed about energy is that it ﬂflows in a preferred direction. This observation is another fundamental law of thermodynamics. Heat flows from a hot object to a cold object. The wind blows from a region of high pressure to an area of low pressure. Forces of nature develop some forms of energy.
- Air bubbles move upwards in the water against gravity because buoyancy forces them to rise.
- Water droplets fall in the atmosphere because the force of gravity pulls them toward the ground.
- Another brilliant observation about energy is that if you have no energy at all, you have no temperature.
3. The concept of absolute zero temperature is a fundamental law of thermodynamics.
The amount of heat transferred by a substance depends on the speed and number of atoms or molecules in motion. The faster the atoms or molecules move, the higher the temperature, and the more atoms or molecules that are in motion.
Temperature, A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale. The most commonly used temperature scale is Celsius (0 degrees C and 100 degrees C) and the Fahrenheit scale (32 degrees F and 212 degrees F).
The amount of heat needed to increase the temperature of a certain mass of a substance by a certain amount is called specific heat, or specific heat capacity. The conventional unit for this is calories per gram per Kelvin.
Newton’s Law of Cooling:
“The rate of change in temperature is proportional to the diﬀerence between the temperature of an object and the surrounding environment.” This results in an exponential reduction in temperature diﬀerence. For example, if a hot object placed in a cold bath, within a certain period, the diﬀerence in their temperatures will decrease by half. Then in that same length of time, the remaining diﬀerence will again reduce by half. This repeated halving of the temperature diﬀerence will continue at regular time intervals until it becomes too small to measure.
Thermal conductivity (k) is the rate at which heat passes through a specified substance. The unit for k is watts(W) per meter (m) per kelvin (K).
Heat can be transferred from one body to another or between a body and the environment by three diﬀerent means: conduction, convection, and radiation. Conduction is the transfer of energy through a solid material. Conduction between bodies occurs when they are in direct contact, and molecules transfer their energy across the interface. Convection is the transfer of heat to or from a fluid medium.