Class 7 Science Question Answers - Temperature And Heat

Short Types Questions

Q.1. What is temperature?

Temperature is a measure of the degree of hotness or coldness of an object. It indicates the direction of the flow of thermal energy, from a hotter object to a cooler object.

Q.2. What is heat?

Heat is a form of energy that flows from a hotter object to a cooler object. It is the energy that causes the temperature of an object to increase or decrease.

Q.3. Name the three temperature scales that are commonly used.

The three temperature scales that are commonly used are Celsius, Fahrenheit, and Kelvin. Celsius and Fahrenheit scales are based on the freezing and boiling points of water, whereas Kelvin is based on the absolute zero temperature.

Q.4. What are the three modes of heat transfer?

The three modes of heat transfer are conduction, convection, and radiation. Conduction is the transfer of heat through a material or between materials in direct contact. Convection is the transfer of heat by the movement of a fluid. Radiation is the transfer of heat through electromagnetic waves.

Q.5. How can we prevent loss of heat from our homes?

We can prevent loss of heat from our homes by insulating our walls, ceilings, and floors. This can be done using materials such as fiberglass, foam, or cellulose. We can also use weatherstripping and caulking to seal any gaps or leaks around doors, windows, and other openings. Additionally, using double-paned windows and installing energy-efficient heating systems can also help to reduce heat loss.

Long Types Questions

Temperature refers to the degree of hotness or coldness of an object or substance. Heat, on the other hand, is a form of energy that flows from one object or substance to another because of a temperature difference. Temperature is a scalar quantity, while heat is a vector quantity. In other words, temperature has only a magnitude, while heat has both magnitude and direction.

Temperature and heat are related to each other in the sense that heat always flows from a body at a higher temperature to a body at a lower temperature. When two bodies at different temperatures come in contact with each other, heat flows from the hotter body to the colder body until they reach thermal equilibrium, i.e., the temperatures of both the bodies become equal. The amount of heat that flows between the bodies is proportional to the temperature difference between them.

Q.2. What are the different temperature scales used to measure temperature? Explain any two in detail.

The three commonly used temperature scales to measure temperature are Celsius, Fahrenheit, and Kelvin scales.

The Celsius scale is based on the freezing and boiling points of water, where 0°C is the freezing point and 100°C is the boiling point of water at sea level. This scale is widely used in most countries around the world.

The Fahrenheit scale is also based on the freezing and boiling points of water but uses different values. In this scale, 32°F is the freezing point, and 212°F is the boiling point of water at sea level. This scale is primarily used in the United States and some other countries.

The Kelvin scale is based on the absolute zero point, which is -273.15°C. This scale is often used in scientific and engineering applications, where temperature measurements need to be precise. The Kelvin scale is the only scale that starts from absolute zero, where all molecular motion ceases.

Q.3. Explain the different modes of heat transfer with examples.

Heat can be transferred in three different ways: conduction, convection, and radiation.

Conduction is the transfer of heat through a material by direct contact. For example, when you touch a hot stove, heat is conducted from the stove to your hand. Another example is a metal spoon getting hot when left in a hot cup of tea.

Convection is the transfer of heat through a fluid, such as air or water, by the movement of the fluid itself. For example, when you boil water in a pan, the heat is transferred from the stove to the water through conduction. As the water heats up, it rises and transfers heat to the surrounding air by convection.

Radiation is the transfer of heat through electromagnetic waves. For example, the heat we receive from the sun is transferred through radiation. When you sit near a fire, the heat you feel is also transferred through radiation.

Q.4. Describe the three modes of heat transfer and give examples of each.

The three modes of heat transfer are conduction, convection, and radiation. Conduction is the transfer of heat through a material by the movement of electrons and atoms. Example: The handle of a hot pan getting hot due to heat conduction from the pan. Convection is the transfer of heat through a fluid (liquid or gas) by the movement of the fluid itself. Example: Heating water in a pot on the stove. Radiation is the transfer of heat through electromagnetic waves. Example: Feeling the warmth of the sun on your face.

Q.5. How can we prevent the loss of heat in our homes during winters? Explain with suitable examples.

We can prevent the loss of heat in our homes during winters by using insulation, sealing gaps in doors and windows, and using energy-efficient appliances. Insulation can be done using materials like fiberglass, cellulose, or foam insulation. Sealing gaps in doors and windows can be done using weatherstripping or caulk. Energy-efficient appliances like LED lights, programmable thermostats, and Energy Star certified appliances can also help reduce energy consumption. For example, using insulated curtains and draft stoppers can prevent cold air from entering the room, thereby reducing the need for heating. Using a programmable thermostat to reduce the temperature at night or when no one is at home can significantly reduce energy consumption.