Count Rumford supervised the drilling of brass cannons in a factory in Bavaria. From his observations, Rumford concluded that heat is not a form of matter.

Work and Heat Heat is the transfer of thermal energy from one object to another because of a temperature difference. Heat flows spontaneously from hot objects to cold objects.

Work and Heat A drill is a machine that does work on the cannon. Remember that no machine is 100% efficient. Some of the work done by the drill is useful, but some energy is lost due to friction. Heat flows from the cannon to a surrounding water bath because the cannon is at a higher temperature than the water.

Temperature What is the temperature of an object related to? Temperature is related to the average kinetic energy of the particles in an object due to their random motions through space.

Temperature Temperature is a measure of how hot or cold an object is compared to a reference point. On the Celsius scale, water freezes at 0°C and boils at 100°C. On the Kelvin scale, absolute zero is the temperature where all molecular motion stops. It is defined as a temperature of 0 Kelvins.

How does heat flow from a high to a low temperature? It does this through collisions. On average, high energy particles lose energy and low energy particles gain energy in collisions. So overall, collisions transfer thermal energy from hot to cold objects.

Thermal Energy What is thermal energy? Thermal energy is the total potential and kinetic energy of all the particles in an object. Thermal energy depends on the mass, temperature, and phase (solid, liquid, or gas) of an object.

Thermal energy depends on mass. A cup full of tea and a pitcher full of tea have the same temperature. However, because the pitcher holds a larger amount, or mass, of tea, it also has more particles than the cup. Because it has more particles it can be said that it has more thermal energy

Thermal energy depends on temperature. If you have a cup of hot tea and a cup of cold tea, they both contain the same number of particles and have the same mass. Because the particles in warmer objects move faster than the particles in colder objects, there are more collisions taking place in the warm cup of tea. Because the particles are moving faster, the average kinetic energy is greater and thus it contains more thermal energy.

Thermal Energy Thermal energy depends on mass and temperature. The tea is at a higher temperature than the lemonade. The lemonade has more thermal energy because it has many more particles.

Thermal Contraction and Expansion What is thermal expansion? Thermal expansion is an increase in the volume of a material due to a temperature increase. Thermal expansion occurs when particles of matter move farther apart as temperature increases.

Thermal Energy If you take a balloon outside on a cold winter day, it shrinks in a process of thermal contraction. As temperature decreases, the particles that make up the air inside the balloon move more slowly, on average. Slower particles collide less often and exert less force. Gas pressure decreases and the balloon contracts.

Thermal Energy If you bring the balloon inside, it expands. Gases expand more than liquids and liquids usually expand more than solids.

Thermal Energy As temperature increases, the alcohol in a thermometer expands, and its height increases in proportion to the increase in temperature. In an oven thermometer, strips of steel and brass expand at different rates as the coil heats up. The coil unwinds, moving the needle on the temperature scale.

Specific Heat What is specific heat? Specific heat is the amount of heat needed to raise the temperature of one gram of a material by one degree Celsius. The lower a material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass.

Specific Heat When a car is heated by the sun, the temperature of the metal door increases more than the temperature of the plastic bumper. The iron in the door has a lower specific heat than the plastic in the bumper.

Specific Heat

Specific Heat In this formula, heat is in joules, mass is in grams, specific heat is in J/g•°C, and the temperature change is in degrees Celsius.

Specific Heat What is a calorimeter? A calorimeter is an instrument used to measure changes in thermal energy. It uses the principle that heat flows from hotter to colder objects until they both reach the same temperature. The thermal energy released by one object is equal to the thermal energy absorbed by another object.

Specific Heat A calorimeter is used to measure specific heat. A sample is heated and placed in the calorimeter. The temperature change is observed.

What is the thermal energy of an object? Assessment Questions What is the thermal energy of an object? the total number of atoms or molecules the total kinetic energy of the atoms or molecules the average kinetic energy of the atoms or molecules the average mechanical energy of the atoms or molecules

What is the thermal energy of an object? Assessment Questions What is the thermal energy of an object? the total number of atoms or molecules the total kinetic energy of the atoms or molecules the average kinetic energy of the atoms or molecules the average mechanical energy of the atoms or molecules ANS: B

What causes a gas to expand when its temperature is increased? Assessment Questions What causes a gas to expand when its temperature is increased? The number of particles increases as temperature increases. Each particle expands as its temperature increases, so the total volume increases. As temperature increases, more electrons leave atoms and move separately. As gas particles move faster, they overcome some forces of attraction.

What causes a gas to expand when its temperature is increased? Assessment Questions What causes a gas to expand when its temperature is increased? The number of particles increases as temperature increases. Each particle expands as its temperature increases, so the total volume increases. As temperature increases, more electrons leave atoms and move separately. As gas particles move faster, they overcome some forces of attraction. ANS: D

Assessment Questions The specific heat of water is 4.18 J/g•°C. How much heat is required to raise the temperature of 1,000 grams of water by 50°C? 83.6 J 83.6 kJ 209 J 209 kJ

Assessment Questions The specific heat of water is 4.18 J/g•°C. How much heat is required to raise the temperature of 1,000 grams of water by 50°C? 83.6 J 83.6 kJ 209 J 209 kJ ANS: D

What property of matter can be measured using a calorimeter? Assessment Questions What property of matter can be measured using a calorimeter? temperature thermal expansion specific heat mass

What property of matter can be measured using a calorimeter? Assessment Questions What property of matter can be measured using a calorimeter? temperature thermal expansion specific heat mass ANS: C

Assessment Questions Temperature is the transfer of thermal energy from one object to another. True False

Assessment Questions Temperature is the transfer of thermal energy from one object to another. True False ANS: F, Heat