What is Thermal Energy? Thermal energy is the amount of heat caused by the motion of atoms in a substance Thermal energy is the kinetic energy of the particles that make up a substance Heat is the energy that is transferred between objects that are at different temperatures Heat moves from hot objects to cold objects as a way to even out the heat Thermal energy, depends partly on temperature, but it also depends on how much of a substance there is Ex: An iceberg has more thermal energy than a pot of hot soup simply because there are more particles in the iceberg, and overall, there will be more movement of the atoms

Measuring Thermal Energy Although both soups are at the same temperature, there is more soup in the pan. So the soup in the pan has more thermal energy than the soup in the bowl.

Transfer of Thermal Energy 1. Energy is transferred from the particles in the juice to the particles in the bottle. These particles transfer energy to the particles in the ice water, causing the ice to melt. 2. Thermal energy continues to be transferred to the water after all of the ice has melted. 3. Eventually, the juice, bottle, and water have the same temperature. The juice and the bottle became colder, and the water became warmer. Juice (25°C) Bottle (25°C) Ice Water (0°C) Juice (9°C) Bottle (9°C) Water(9°C)

What is Temperature? You probably think of temperature as a measure of how hot or cold something is However, coldness is really just a lack of heat A freezer may have less heat than a refrigerator, but it still has some heat Scientifically, temperature is a measure of the average kinetic energy of the particles in an object Because particles are in motion, they have kinetic energy The more kinetic energy in a substance’s particles, the higher the temperature of the object. The more kinetic energy in a substance’s particles, the more thermal energy it contains

Low- temperature particles have a low average kinetic energy. High- temperature particles have a high average kinetic energy. The particles of hot cocoa move faster than those of cold chocolate milk. Cold Chocolate MilkHot cocoa

Temperature Scales You will probably hear the temperature in the daily weather report given in the Fahrenheit scale (°F) Scientists, however, often use the Celsius scale (°C) –Pure water freezes at 0° Celsius, and boils at 100° Celsius A third scale, the Kelvin scale, is divided into units called kelvins (K)- but not degrees kelvin The lowest temperature in the Kelvin scale is 0 K, which is called absolute zero (-459°F) This is the temperature at which all molecular motion stops It is not possible to actually reach absolute zero, although temperatures very close to 0 K have been reached in laboratories

Measuring Temperature Many thermometers are thin glass tubes filled with a liquid Mercury and alcohol are often used because they remain in liquid form over a large temperature range Thermometers can measure temperature because of a property called thermal expansion Thermal expansion is an increase in the size of a substance in response to an increase in its temperature As the temperature of the liquid decreases, its volume decreases. As the temperature of the liquid increases, its volume increases. Temperature changes cause the level of the liquid inside a thermometer to rise and fall.

Thermal Expansion The gap in the bridge allows the concrete to expand and contract without breaking. The fire heats the air, making the particles expand and become less dense. This gets the hot-air balloon off the ground.

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