# Chapter 5 – Heat

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

Heat is the energy form that makes anything hot. Hot and cold are two types of sensations that we feel in our day-to-day life. When we feel cold in winters, we sit in sunlight or in front of a heater to get the feeling of warmth. Have you ever wondered how the sun or any hot substance gives us a warm sensation or how cooked rice gets cold after some time? Learn more about heat and how heat transfers in this chapter.

#### Hot and Cold

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 as a Form of Energy and its Units

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.

#### Effects of Heat

There are different effects of heat:

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

#### Heat and Temperature

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.

#### Clinical Thermometer

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.

#### Digital 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).

#### Laboratory thermometer

• 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.

#### Transfer of Heat

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

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.

1. 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.

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.

#### FAQs

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.

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### High School Physics

• Alternating Current
• Atoms
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• Dual nature of Radiation and Matter
• Electric Charges and Fields
• Electricity
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• Electromagnetic Waves
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### High School Chemistry

• Acids, Bases and Salts
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### High School Biology

• Absorption and Movement of Water in Plants
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### High School Math

• Algebra – Arithmatic Progressions
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### Middle School Science

• Acids, Bases And Salts
• Air and Its Constituents
• Basic Biology
• Body Movements
• Carbon and Its Compounds
• Cell – Structure And Functions
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• Chemical Effects Of Electric Current
• Coal And Petroleum
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• Elements and Compounds
• Fibre To Fabric
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• Force And Pressure
• Forests: Our Lifeline
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• Garbage In, Garbage Out
• Getting To Know Plants
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• Heat
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• Matter and Its States
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• Micro Organisms: Friend And Foe
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• Reaching The Age Of Adolescence
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• Separation Of Substances
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• Sound
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• Structure of Atom
• Synthetic Fibers And Plastics
• The Living Organisms And Their Surroundings
• Transfer of Heat
• Transformation of Substances
• Transportation In Animals And Plants
• Universe
• Waste-water Story
• Water: A Precious Resource
• Weather, Climate And Adaptations Of Animals To Climate
• Winds, Storms And Cyclones

### Middle School Math

• Area and Its Boundary
• Boxes and Sketches
• Data Handling
• Fun With Numbers
• Heavy and Light
• How Many
• Long And Short
• Mapping
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• Multiplication and Factors
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• Numbers
• Parts and Wholes
• Pattern Recognition
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• Rupees And Paise
• Shapes And Angles
• Shapes And Designs
• Shapes and Space
• Similarity
• Smart Charts
• Squares
• Subtraction
• Tables And Shares
• Tenths and Hundredths
• Time