Heat capacity

Heat capacity or thermal capacity is a measurable physical quantity equal to the ratio of the heat added to (or removed from) an object to the resulting temperature change. The SI unit of heat capacity is joule per kelvin and the dimensional form is L²MT⁻²Θ⁻¹. Specific heat is the amount of heat needed to raise the temperature of a certain mass by 1 degree Celsius.

Heat capacity is an extensive property of matter, meaning it is proportional to the size of the system. When expressing the same phenomenon as an intensive property, the heat capacity is divided by the amount of substance, mass, or volume, so that the quantity is independent of the size or extent of the sample. The molar heat capacity is the heat capacity per unit amount (SI unit: mole) of a pure substance and the specific heat capacity, often simply called specific heat, is the heat capacity per unit mass of a material. Occasionally, in engineering contexts, the volumetric heat capacity is used.

Temperature reflects the average randomized kinetic energy of constituent particles of matter (e.g. atoms or molecules) relative to the centre of mass of the system, while heat is the transfer of energy across a system boundary into the body other than by work or matter transfer. Translation, rotation, and vibration of atoms represent the degrees of freedom of motion which classically contribute to the heat capacity of gases, while only vibrations are needed to describe the heat capacities of most solids , as shown by the Dulong–Petit law. Other, more exotic contributions can come from magnetic and electronic degrees of freedom in solids, but these rarely make substantial contributions.

Khan Academy

Khan Academy is a non-profit educational organization created in 2006 by educator Salman Khan with the aim of providing a free, world-class education for anyone, anywhere. The organization produces short lectures in the form of YouTube videos. In addition to micro lectures, the organization's website features practice exercises and tools for educators. All resources are available for free to anyone around the world. The main language of the website is English, but the content is also available in other languages.

History

The founder of the organization, Salman Khan, was born in New Orleans, Louisiana, United States to immigrant parents from Bangladesh and India. After earning three degrees from the Massachusetts Institute of Technology (a BS in mathematics, a BS in electrical engineering and computer science, and an MEng in electrical engineering and computer science), he pursued an MBA from Harvard Business School.

In late 2004, Khan began tutoring his cousin Nadia who needed help with math using Yahoo!'s Doodle notepad.When other relatives and friends sought similar help, he decided that it would be more practical to distribute the tutorials on YouTube. The videos' popularity and the testimonials of appreciative students prompted Khan to quit his job in finance as a hedge fund analyst at Connective Capital Management in 2009, and focus on the tutorials (then released under the moniker "Khan Academy") full-time.

Heat

In physics, heat is energy as it spontaneously passes between a system and its surroundings, other than as work or with the transfer of matter. In thermodynamics, finer detail of the process of transfer is in principle unspecified. When there is a suitable physical pathway, heat transfer occurs from a hotter to a colder body. The transfer can be direct, by contact, from the source to the destination body, as in conduction combined with radiation, or remote, as in radiation without conduction; or indirect, by conduction and radiation through a thick solid wall, or by way of an intermediate fluid body, as in convective circulation.

Originally, quantity of heat transferred was measured by how much it changed the states of participating bodies, for example, as amount of ice melted, or change in temperature, without work or matter transfer. Such measurement is possible because many bodies, over most temperature ranges, expand reversibly on being heated. This is called thermal expansion.