Many things around us can be hot or cold, like tea or boiling water is hot, and ice or ice cream is cold. This is not just a sensation but a form of energy called heat energy. Heat can be termed as an energy which makes you feel hot or warm or we can say scientifically that it is a form of energy where the transfer of energy from a hot to a cooler object takes place. 

Heat transfer

The flow of thermal energy that arises from temperature variations is called Heat transfer. Thermal energy flows whenever two elements of varied temperatures are near one another. heat is the transfer of energy from a hotter object to a cooler object, like if a spoon is left in a bowl of hot soup, then the heat from the soup is transferred to the spoon and it becomes hot. 

• Temperature is a measure of the internal heat of an object or an individual’s body
• The thermometer that is used to measure the temperature of a human body is called a clinical thermometer. The temperature scale ranges from 35°C to 42°C. The regular temperature of a human body is 37°C Mercury, which is a toxic substance, is used in thermometers. Digital thermometers that do not use mercury are also available for temperature checks
• For other purposes, laboratory thermometers are used. Their range varies from 10°C to 110°C
• The heat transfers from a high body temperature to a low body temperature. There are three ways in which heat can flow: Convection, Conduction, and Radiation
  • In Conduction, heat is generally transferred to solids
  • Conductors are elements that permit heat transfer through them effortlessly. For example Copper, Aluminium, and Iron

• • Insulators are materials that do not allow heat to pass through them easily. For example, Wood and Plastic
  • In Convection, the heat transfer executes itself through gases and liquids. Air and water are bad conductors of heat
  • In Radiation, for the transfer of heat, there is no requirement of any medium. The heat from the Sun that reaches us is an example of radiation

• Dark surfaces absorb more heat and hence, dark-coloured clothes are more comfortable in the winter. On the contrary, Light-coloured clothes reflect more heat and are comfortable to wear during the summer season
• Wool is a poor conductor of heat. Air gets trapped in between its fibre and prevents the flow of heat from our body to the cold surrounding, making us feel warm

This transfer of heat can occur in different ways. They are:

• Conduction:

This is a process of heat transfer where the heat is transferred from the hot part to the cold part of the object. Example – The handle of a pan gets hot when the pan becomes hot and so a wooden or plastic handle is made for them 

The substances that allow the heat to pass through them are termed as conductors. Example – iron, copper, etc. 

The substances that do not allow the heat to transfer through them are called insulators or poor conductors. Example – wood, plastic.

• Convection:

This  is the form of heat transfer in liquids and gases where the heat is transferred by the movement of the heated molecules within them. Example – boiling of water. 

The molecules of the fluid or gas near the source of heat become hot and rise up and this is replaced by the colder molecules in the fluid or air. They also get heated up and rise till the entire fluid or air is heated. 

This is the principle behind the interesting feature in the coastal areas called the sea and land breeze.

• Radiation: 

This is the form of heat transfer where a medium like air or liquid is not required to transfer the heat energy. Example – Heat from the sun, a hot utensil becomes cool after some time by transfer of heat to surroundings this way. 

All the hot bodies are capable of radiating heat. 

Heat Waves: An interesting phenomenon:

• The sea breeze is the air from the sea. The temperature of the land rises earlier than the water during the daytime. Due to this reason, the air over the ground becomes hotter, and the cold air from the ocean hurries towards the ground to absorb hot air. The hot air from the ground shifts towards the sea to complete the process
• At night it is completely the opposite of the day. The land cools down faster than the water. So, the cold air from the ground rushes towards the sea. This cycle is known as the Land breeze

Conclusion-

Heat is the energy transmitted from one object to another as a consequence of a temperature differential. We can feel heat with the rise of temperature. When two bodies of differing temperatures come into contact, energy is transferred—that is, heat flows—from the hotter to the colder. The consequence of this transfer of energy is typically, but not always, a rise in the colder body’s temperature and a reduction in the hotter body’s temperature.