In our routine life, we touch different things. Few of them are hot, and others are cold. For example, a pan kept on a burning stove is hot, while its handle is not hot. Similarly, ice or the container containing ice is very cold. Among these hot and cold objects, some objects are very hot to touch, while others are less hot. Similarly, ice is cold and cannot be held for longer, while the other things that we keep in the refrigerator are not as cold as ice. You can only touch these objects and find if it is hot, very hot, cold, very cold, or at room temperature. But the exact way to do this is to find the temperature that can be measured using the thermometer.

Heat is a form of energy and it moves from a hot body to a cold body. Heat transfers from the hotter body to the colder body. Heat is measured in Joules as SI unit and CGS unit of heat is erg. Temperature can be used to know how hot the body is. There are different units of temperature, of which Celsius and Fahrenheit are the most commonly used.

There are different effects of heat:

• Increases the temperature
• Increases the volume
• Changes the state of matter

Temperature is the degree of coldness or hotness of any object. Temperature is the property of an object that helps to determine whether the object is hot or cold. If the temperature value is high, it indicates the object is hot. On the other hand, low temperature describes that the object is cold. To exemplify, boiling water is very hot in touch, and melting ice is very cold.

Temperature can be measured using a thermometer. 

There are different kinds of thermometers used for multiple purposes, hence having different scales of measurement. For example, a laboratory thermometer has a scale ranging from 0 degrees to 100 degrees with 100 divisions, and each division represents a degree. The laboratory thermometer and clinical thermometer have mercury in the glass tube. As the thermometer bulb gets touched with the object, the mercury inside it expands and rises. The position of the mercury on the thermometer scale gives the temperature of an object.

A clinical thermometer is mainly used to measure the temperature of the human body. If the temperature is more than a normal body temperature, the person is said to have a fever, and the doctor recommends medicines. The clinical thermometer is made of a glass tube having a thin bore inside. A glass bulb is present at one end of the thermometer containing mercury.

Features of Clinical Thermometer

• A clinical thermometer is a short-range thermometer for temperature measurement. The scale of the clinical thermometer ranges from 35 degrees to 42 degrees as the human temperature never goes beyond this range.
• Mercury is preferred in thermometers as it is in a liquid state over a wide temperature range. Moreover, it does not stick to the glass and has silver-grey color, thus easy to observe.
• A clinical thermometer is designed such that a small change of 0.2 degrees can also be noticed.
• The tube has a bend that prevents the mercury to flow into the bulb until the temperature is read by the user.
• If the level of mercury is low, a small jerk is given to the thermometer.

• In this digital world, the body temperature gets measured by digital thermometers.
• Digital thermometers work with the help of tiny dry cells.
• It is a risk-free and safer tool, consisting of no mercury (an injurious matter or substance).

• A laboratory thermometer has a glass body in the form of a tube.
• A laboratory thermometer can measure the range of temperature between 10 to 110 °C.
• It contains mercury that expands in the glass capillary of a thermometer when heated.

Heat flows from an object at a higher temperature to another one at a lower temperature is called a transfer of heat. Let’s suppose we dip a spoon in hot water, the spoon temperature spikes, and a spoon will become hot. The flow of heat doesn’t work when the two objects are of the same temperature.

Methods of Heat Transfer

There are below three methods of heat transfer:

1. Conduction
2. Convention
3. Radiation

1. Conduction
   Conduction is a mode of the transfer of heat from a hot material to a cold material without the material’s movement. Heat gets transferred, in the solids, by the conduction process. 

   Insulator and Conductor of Heat
   Materials through which the heat gets conducted easily are known as conductors of heat. Aluminum, iron, silver, and more are good heat conductors.
   Some materials that don’t let the heat get conducted through them are insulators of heat. Glass, plastic, and wood are good insulators of heat.

2. Convection
   Convection is the mode of the transfer of heat from a hotter part to a cold part of fluid by its movement. The process of convection happens in gases and liquids only because the particles present in a fluid move without interruption. On the other hand, the same doesn’t happen with solids due to no movement of particles as they are stable.
   Convection in Air
   Air transfers heat from its hotter to the colder parts by the convection process as it is a poor conductor of heat.
   Convection in Water
   Water doesn’t transfer heat by the process of conduction, but the process of convection, because it is a poor conductor of heat.

3. Radiation
   The transfer of heat mode, through which heat energy from hot to the cold body using heat rays with no material medium between, is called radiation. For example, the heat of the sun travels to the earth by the radiation process. Despite being far away and the vacuum between the sun and the earth, the sun’s heat reaches the earth. It is because the sun is extremely hot and sends its infrared rays or heat radiation in all directions equally. Heat transfer from a hot object to a cold object by the radiation process does not need any medium.

   To conclude, heat is a form of energy that flows from a hotter body to a colder one. There are different units of temperature that measure heat, viz. Fahrenheit and celsius. Temperature is measured using a thermometer. There are different thermometers, such as clinical, digital, and laboratory. Clinical thermometer and laboratory thermometer contain mercury inside it. Transfer of heat occurs through conduction, convection, and radiation.

1. What is the unit of heat?
   Heat is the form of energy that transfers from a hot body to a colder one.
2. What are the effects of heat?
   Heat changes the state of matter and increases its temperature.
3. What are different methods of transfer of heat?
   Conduction, convection, and radiation are three methods of transfer of heat.
4. What is a digital thermometer?
   A digital thermometer works using an electronic cell.
5. What is conduction?
   Conduction is a method of transfer of heat that occurs in solids.