(9)+Temperature+and+Heat

PAGE EDITOR(S): Georges Cuissart de Grelle, David Iparraguirre, Javier Henriquez, Najib Wahab

= TEMPERATURE AND ...=

1) __Temperature__: a measure of the average kinetic energy of the molecules in a substance 2) __Heat (Q)__: a transfer of energy due to a temperature difference (The heat is also a super awesome Miami basketball team)
 * __Good Thermal conductor will transfer two things:__**
 * Heat energy is measured in joules.

1) __Conduction__: A transfer of energy as heat through physical contact between two substances at different temperatures. 2) __Convection__: A transfer of energy as heat due to the bulk movement of a fluid. 3) __Radiation__: A transfer of energy as heat due to electromagnetic waves.
 * __Three Main Methods of Energy Transfer as Heat__**

media type="youtube" key="VzE_IPedujc" height="344" width="425"

1) __Conduction__: Heating up a pan on a stove, like if you were boiling water. The stove heats up and since the pan is resting on the stove, through conduction (physical contact), the pan heats up. 2) __Convection__: Cooking pasta in boiling water. The stove heats up the pasta by boiling the water, through means of convection. 3) __Radiation__: A microwave...
 * Examples of each:**

Heat=
 * __Rate at which energy transfers as heat through conduction:__**

Cross multiply the time (t) so you get: Heat (Q) = Q/t = KA **//T//** t/L

k=Thermal conductivity constant A=Area **//T//** = Change in temperature t= Time L=Length





Heat flows from hot to cold. The faster moving molecules excite the slower one, getting them to move faster...

**Heat is energy in transit from hot to cold.**  (a) Heat flows from the hotter coffee cup to the colder hand. (b) Heat flows from the warmer hand to the colder glass of ice water.

media type="youtube" key="G92QsfSStUw" height="340" width="560" Notice the Heat transfer from Dwayne Wade to the crowd through means of conduction, convection, and radiation, all at the same time... The physical contact between the players, the hot air from D-Wade's body and from the screaming Heat fans, and the radiation from Dwayne for being awesome...

=__Thermal Expansion__=
 * ~ Coefficients of Thermal Expansion for Solids and Liquids ||

__Linear Expansion__ - Over small temperature ranges, the fractional thermal expansion of uniform linear objects is proportional to the temperature change - The **linear expansion** of a solid depends on its initial length, temperature change, and the type of material it is made from. - The coefficient of linear expansion is different for different materials
 * |||||||| Coefficient of Thermal Expansion (C°)-1 ||
 * Substance || Linear (//α//) || Volume (β) ||
 * //**Solids**// ||  ||   ||
 * Aluminum || 23 × 10-6 || 69 × 10-6 ||
 * Brass || 19 × 10-6 || 57 × 10-6 ||
 * Concrete || 12 × 10-6 || 36 × 10-6 ||
 * Copper || 17 × 10-6 || 51 × 10-6 ||
 * Glass (common) || 8.5 × 10-6 || 26 × 10-6 ||
 * Glass (Pyrex) || 3.3 × 10-6 || 9.9 × 10-6 ||
 * Gold || 14 × 10-6 || 42 × 10-6 ||
 * Iron or steel || 12 × 10-6 || 36 × 10-6 ||
 * Lead || 29 × 10-6 || 87 × 10-6 ||
 * Nickel || 13 × 10-6 || 39 × 10-6 ||
 * Quartz (fused) || 0.50 × 10-6 || 1.5 × 10-6 ||
 * Silver || 19 × 10-6 || 57 × 10-6 ||
 * //**Liquids**// ||  ||   ||
 * Benzene || — || 1240 × 10-6 ||
 * Carbon tetrachloride || — || 1240 × 10-6 ||
 * Ethyl alcohol || — || 1120 × 10-6 ||
 * Gasoline || — || 950 × 10-6 ||
 * Mercury || — || 182 × 10-6 ||
 * Methyl alcohol || — || 1200 × 10-6 ||
 * Water || — || 207 × 10-6 ||  ||  ||

Equation:

//T= change in temperature// ** //Lo= initial length L= change in length //  = coefficient of linear expansion **

__**Area Expansion**__  or

ΔA = A0 2α ΔT or <span style="-webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; border-collapse: collapse;"><span style="-webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; font-family: Times; font-size: 17px; line-height: normal;">

<span style="-webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; font-family: Times; font-size: medium; line-height: normal;">
 * __Volume Expansion__**

or

<span style="-webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; font-family: Palatino,serif; font-size: 14px; line-height: 18px; white-space: nowrap;">Δ//V// = β//V//**0**Δ//T

or//



* 3α=β

__Thermal Expansion Practice Problems__<span style="-webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; border-collapse: separate; font-family: helvetica,sans-serif; font-size: 12px; line-height: 18px;">
 * 1) A steel bridge is built in several segments, each 20 m long. The gap between segments is 4 cm at 18 ℃. What is the maximum temperature that the bridge can manage before buckling?
 * 2) How much taller is the Eiffel Tower on the hottest day of the summer (25 ℃) than the coldest day of the winter (2 ℃)? The tower is 324 m tall measured from the top of the flagpole. Assume the tower is built of structural steel.

Most bridges are built with gaps that allow the bridge to expand without cracking the material.

//Paul Natland// __http://hyperphysics.phy-astr.gsu.edu/HBASE/thermo/heatra.html__** [] [|The Physics Hypertextbook]
 * __SOURCES__