Heat And Temperature Quiz For Class 7 Quiz

The boiling point for water on the Celsius scale is 100 degrees. This means that at this temperature, water changes from a liquid to a gas state. It is an important reference point for temperature measurement and is widely used in scientific experiments and everyday life.

The Sun is a natural source of radiation. It emits various forms of electromagnetic radiation, including visible light, ultraviolet rays, and infrared radiation. This radiation is essential for life on Earth as it provides heat and light energy. However, excessive exposure to certain types of solar radiation, such as ultraviolet rays, can be harmful to living organisms. Therefore, it is important to protect oneself from overexposure to the Sun's radiation by using sunscreen, wearing protective clothing, and seeking shade when necessary.

The correct answer is that all substances are made of tiny particles too small to be seen. This is a fundamental concept in the particle model of matter, which states that all matter is composed of particles that are too small to be seen with the naked eye. These particles are constantly in motion and have spaces between them. This concept helps explain various properties of matter, such as its ability to change shape and size, and its behavior under different conditions.

Conduction is the process of heat transfer through direct contact between objects. When two objects at different temperatures touch, heat flows from the warmer object to the cooler one until thermal equilibrium is reached. This occurs in solids, particularly metals, where particles are tightly packed and can easily transfer kinetic energy. Convection involves heat transfer in fluids (liquids or gases), radiation transfers heat through electromagnetic waves, and evaporation refers to the process of a liquid turning into vapor, not directly related to heat transfer via contact.

Fossil fuels are non-renewable resources because they are formed from the remains of plants and animals that lived millions of years ago, and their formation takes a very long time. Once these fossil fuels, such as coal, oil, and natural gas, are extracted and burned, they cannot be replaced within a human lifespan. Therefore, their supply is limited and they will eventually run out if consumed at the current rate. This is why it is important to explore and develop alternative, renewable sources of energy to reduce our dependence on fossil fuels.

Temperature measures the average kinetic energy of the particles in a substance. It indicates how fast particles are moving: the higher the temperature, the faster the particles move. Heat, on the other hand, is the transfer of energy between substances due to a temperature difference. Thermal energy refers to the total kinetic energy of particles in an object, and specific heat is the amount of heat required to raise the temperature of a substance by 1 degree.

A block of ice can radiate and absorb heat because all objects with a temperature above absolute zero emit thermal radiation. This means that even though the ice is cold, it still emits some amount of thermal energy in the form of electromagnetic waves. Additionally, the ice can absorb heat from its surroundings through conduction or convection, allowing it to melt and increase in temperature. Therefore, it is true that a block of ice can both radiate and absorb heat.

Deposition is a phase transition in which a gas transforms directly into a solid without passing through the liquid phase. This process occurs when the temperature of a gas drops below its deposition point, causing the gas molecules to lose energy and come together to form a solid. In contrast, freezing refers to the transition of a liquid to a solid, while evaporation and condensation involve the phase changes between liquid and gas. Deposition is the specific term used for the direct transition from gas to solid.

Chemical energy refers to the energy stored in the bonds of chemical compounds, such as coal and wood. When these substances undergo combustion, the bonds are broken and energy is released in the form of heat and light. Coal and wood are examples of fossil fuels, which contain stored chemical energy that can be harnessed and converted into other forms of energy, such as electricity. Therefore, the given answer "Energy from Coal and wood" correctly identifies chemical energy as the energy derived from these sources.

Radiation is the fastest process of heat transfer because it does not require any medium to transfer heat. It can occur through empty space and is not dependent on direct contact between objects. Radiation involves the emission of electromagnetic waves, such as infrared radiation, which can travel at the speed of light. Conduction and convection, on the other hand, require a medium, such as a solid or a fluid, to transfer heat and are generally slower processes.