Physics Chapter on Heat Energy and Temperature

Heat energy flows from hot to cold bodies
Calorie is a unit of heat
1 Joule = 0.24 calories (approximately)
1 Joule = 10⁷ erg
Temperature determines the direction of heat flow
The amount of heat energy in a body depends on its mass, temperature and the nature of the material.
The SI unit of temperature is Kelvin (K).
The relation between Celsius and Kelvin scales is tK = 273 + t°C
The temperature of a body is related to the average kinetic energy of its molecules.
The temperature at which pressure and volume of a gas becomes zero is 0 K.
The steam point on the Fahrenheit scale is 212°F.
The increase in the length of a solid on heating is called linear expansion.
Liquids expand more than solids and gases expand more than liquids when heated.
Water expands when cooled from 4°C to 0°C. This is known as anomalous expansion.
The density of water is maximum at 4°C, with a value of 1000 kg m^-3.
Ice is a poor conductor of heat, acting as an insulator.

Heat is the form of energy transferred between two bodies at different temperatures. The SI unit of heat is Joule (J).
Heat flows from a hotter body to a colder body.

An ecosystem is a unit comprised of biotic (living organisms) and abiotic (non-living factors) components.
A food chain is a linear sequence of organisms where each organism feeds on the previous one, illustrating the flow of energy.

The sun is the primary source of energy for all ecosystems.
Green plants are crucial to ecosystems as they produce food through photosynthesis, using sunlight as energy.

The ultimate source of energy is the sun.
Renewable sources of energy can be continuously obtained over a long period of time.
Kinetic energy is associated with the movement of an object.
The solar constant is 1.34 kW m^-2.
The correct renewable sources of energy are biomass and nuclear fuel.
Geothermal energy originates from the heat within the Earth.

Characteristics of a good energy source include consistent supply and safe use.
Renewable resources, like wood and water, can be replenished, while non-renewable resources, like fossil fuels, cannot.

The conversion of energy from one form to another often results in some energy becoming unusable (e.g., heat).
Solar cells convert light energy directly into electrical energy.
Solar power plants use mirrors to concentrate sunlight to heat water and produce steam, which then drives turbines to generate electricity.
Advantages of hydroelectricity include its clean source and renewing nature. Disadvantages include environmental impacts from dam construction.
Nuclear energy has high-energy output from a small amount of fuel but comes with the risk of radioactive waste.
Four ways to use energy judiciously are efficient energy use, utilizing renewable sources, protecting forests, and responsible population control.

The gases that absorb long-wavelength infrared radiation are called greenhouse gases.
Carbon dioxide is a greenhouse gas.
Increased carbon dioxide in the atmosphere leads to increased temperature.
Without the greenhouse effect, the average temperature of Earth would be -18°C.
Global warming means a rise in average global temperatures due to increased greenhouse gases.

The increase in carbon dioxide in the atmosphere is primarily due to human activities, like burning fossil fuels, deforestation, and manufacturing.
Greenhouse gases like carbon dioxide and methane trap heat in the Earth's atmosphere, causing global warming.
Ways to minimize the impact of global warming include transitioning to renewable energy sources, using more energy-efficient vehicles and practices, controlling population, and reducing wasteful energy consumption.