Forms of Energy

The transfer of heat by direct contact between objects or particles. Conduction The transfer of heat by direct contact between objects or particles. No. 6

Conduction Thermal energy is transferred from place to place by conduction, convection, and radiation. Conduction is the transfer of thermal energy by collisions between particles in matter. Conduction occurs because particles in matter are in constant motion. 9/11/2018 Physical Science

Radiation No. 4 Radiation is the transfer of energy by electromagnetic waves. Heat transferred through space. EXAMPLE: The sun’s rays causing a sunburn.

Radiation Almost no matter exists in the space between Earth and the Sun, so heat cannot be transferred by conduction or convection. Instead, the Sun’s heat reaches Earth by radiation. 9/11/2018 Physical Science

Radiant Energy and Matter When radiation strikes a material, some of the energy is absorbed, some is reflected, and some may be transmitted through the material.

Radiant Energy and Matter Transferring Thermal Energy Radiant Energy and Matter The amount of energy absorbed, reflected, and transmitted depends on the type of material. Materials that are light-colored reflect more radiant energy, while dark-colored materials absorb more radiant energy. 9/11/2018 Physical Science

Convection Heat transferred by the movement of molecules within a substance. Movement occurs from warmer areas to cooler areas.

Convection Liquids and gases can flow and are classified as fluids. In fluids, thermal energy can be transferred by convection. No. 13 Convection is the transfer of thermal energy in a fluid by the movement of warmer and cooler fluid from place to place. 9/11/2018 Physical Science

Convection When conduction occurs, more energetic particles collide with less energetic particles and transfer thermal energy. When convection occurs, more energetic particles move from one place to another. As the particles move faster, they tend to be farther apart. As a result, a fluid expands as its temperature increases. 9/11/2018 Physical Science

Convection Current The movement of a substance that is caused by differences in temperature and density. EXAMPLES: wind boiling water NATURE WANTS EVERYTHING TO BALANCE ! !

Conduction, Convection, Radiation 9/11/2018 Physical Science

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Conductors Conductors are materials that transfer heat easily. Examples: metals like copper and gold

silver copper gold aluminum iron steel brass bronze mercury graphite Conductors silver copper gold aluminum iron steel brass bronze mercury graphite dirty water concrete 9/11/2018 Physical Science

Heat Conductors The rate at which heat moves depends on the material. Heat moves faster by conduction in solids and liquids than in gases. In gases, particles are farther apart, so collisions with other particles occur less frequently than they do in solids or liquids. 9/11/2018 Physical Science

Heat Conductors The best conductors of heat are metals. In a piece of metal, there are electrons that are not bound to individual atoms, but can move easily through the metal. 9/11/2018 Physical Science

Insulators An insulator is a material that does not transfer heat easily. Examples: liquids and gases A jacket

Insulators Insulators glass rubber oil asphalt fiberglass porcelain ceramic quartz (dry) cotton (dry) paper (dry) wood plastic air diamond pure water 9/11/2018 Physical Science

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Temperature and Heat Matter in Motion The faster they move, the more kinetic energy they have. This figure shows that particles move faster in hot objects than in cooler objects. 9/11/2018 Physical Science

Heating and Cooling cont… No. 12 Heat energy always moves from: HOT object COOLER object e.g.Cup of water at 20 °C in a room at 30°C - gains heat energy and heats up – its temperature rises Cup of water at 20 °C in a room at 10°C loses heat energy and cools down – its temperature will fall.

Temperature and Heat Temperature No. 5 The temperature of an object is a measure of the average kinetic energy of the particles in the object. As the temperature of an object increases, the average speed of the particles in random motion increases. 9/11/2018 Physical Science

Temperature In SI units, temperature is measured in kelvin (K). A more commonly used temperature scale is the Celsius scale. One kelvin is the same as one degree Celsius. No. 1 Measure of kinetic energy of molecules Thermometer Fahrenheit Celsius Kelvin 9/11/2018 Physical Science

Temperature and Heat Thermal Energy The sum of the kinetic and potential energy of all the particles in an object is the thermal energy of the object. 9/11/2018 Physical Science

Thermal Energy Because the kinetic energy of the butter particles increased as it warmed, the thermal energy of the butter increased. Measurement related to the quantity of molecules. 9/11/2018 Physical Science

Thermal Energy and Temperature When the temperature of an object increase, the average kinetic energy of the particles in the object increases. Because thermal energy is the total kinetic and potential energy of all the particles in an object, the thermal energy of the object increases when the average kinetic energy of its particles increases. 9/11/2018 Physical Science

Thermal Energy and Mass There are twice as many water molecules in the beaker as there are in the glass. So the total kinetic energy of all the molecules is twice as large for the water in the beaker. 9/11/2018 Physical Science

Thermal Energy and Mass As a result, the water in the beaker has twice as much thermal energy as the water in the glass does. If the temperature doesn’t change, the thermal energy in an object increases if the mass of the object increases. 9/11/2018 Physical Science

Heat No. 12 Heat is thermal energy that flows from something at a higher temperature to something at a lower temperature. Heat is a form of energy, so it is measured in joules-the same units that energy is measured in. Heat always flows from warmer to cooler materials. 9/11/2018 Physical Science

Specific Heat As a substance absorbs heat, its temperature change depends on the nature of the substance, as well as the amount of heat that is added. The amount of heat that is needed to raise the temperature of 1 kg of some material by 1°C is called the specific heat of the material. Specific heat is measured in joules per kilogram Kelvin [J/(kg °C)]. 9/11/2018 Physical Science

Specific Heat

Specific Heat

Specific Heat Equation If Q is the change in thermal energy and C is specific heat, the change in thermal energy can be calculated from the following equation:

Specific Heat Equation amount of heat transferred = mass x change in temperature x specific heat q = m(∆T)Cp

Can you picture a piece of aluminum foil that is taken out of an oven. Example: Aluminum has a specific heat of 0.902 J/g x oC.   How much heat is lost when a piece of aluminum with a mass of 23.984 g cools from a temperature of 415.0 oC to a temperature of 22.0 oC? Step 1:  First read the question and try to understand what they are asking you.  Can you picture a piece of aluminum foil that is taken out of an oven.  Imagine the aluminum losing heat to its surroundings until the temperature goes from 415.0 oC to  22.0 oC.

Step 2:  Write the original formula.

Step 3: List the known and unknown factors Step 3:  List the known and unknown factors.   Looking at the units in the word problem will help you determine which is which. q = ? m = 23.984 g ∆T = (415.0 oC - 22.0 oC) = 393.0 oC     (remember, they asked for the change in temperature) Cp =  0.902 J/g x oC

Step 4.  Substitute your values into the formula q = ? m = 23.984 g DT = (415.0 oC - 22.0 oC) = 393.0 oC   Cp =  0.902 J/g x oC

Water as a Coolant Compared with the other common materials in the table, water has the highest specific heat. The specific heat of water is high because water molecules form strong bonds with each other. 9/11/2018 Physical Science

Temperature and Heat Water as a Coolant Because water can absorb heat without a large change in temperature, it is useful as a coolant. A coolant is a substance that is used to absorb heat. Compared to other materials, the temperature of water will increase less. 9/11/2018 Physical Science

Temperature and Heat Water as a Coolant When heat is added, some of the added heat has to break some of these bonds before the molecules can start moving faster. 9/11/2018 Physical Science

Measuring Specific Heat Temperature and Heat Measuring Specific Heat The specific heat of a material can be measured using a device called a calorimeter. In a calorimeter, a heated sample transfers heat to a known mass of water. 9/11/2018 Physical Science

Measuring Specific Heat Temperature and Heat Measuring Specific Heat The specific heat of a material can be measured using a device called a calorimeter. In a calorimeter, a heated sample transfers heat to a known mass of water. 9/11/2018 Physical Science

Collisions Transfer Thermal Energy Transferring Thermal Energy Collisions Transfer Thermal Energy Thermal energy is transferred when one end of a metal spoon is heated by a Bunsen burner. The kinetic energy of the particles near the flame increases. 9/11/2018 Physical Science

Collisions Transfer Thermal Energy Transferring Thermal Energy Collisions Transfer Thermal Energy When heat is transferred by conduction, thermal energy is transferred from place to place without transferring matter. Thermal energy is transferred by the collisions between particles, not by movement of matter. 9/11/2018 Physical Science

Radiation in Solids, Liquids, and Gases Transferring Thermal Energy Radiation in Solids, Liquids, and Gases This energy then travels through the space between molecules, and is absorbed and emitted by other molecules. Because molecules are much farther apart in gases than in solids or liquids, radiation usually passes more easily through gases than through solids or liquids. 9/11/2018 Physical Science

Transferring Thermal Energy Controlling Heat Flow Almost all living things have special features that help them control the flow of heat. For example, the Antarctic fur seal’s thick coat helps keep it from losing heat. This helps them survive in a climate in which the temperature is often below freezing. 9/11/2018 Physical Science

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What happens to the temperature of a block of ice when you put a Bunsen burner underneath it? You might think that the temperature goes up smoothly, but that's not what happens. The graph of temperature against time is called a heating curve. Let's look at the heating curve for water. 9/11/2018 Physical Science

Phase Changes 9/11/2018 Physical Science

Phase Changes 9/11/2018 Physical Science

Phases Changes 9/11/2018 Physical Science

The heat (or enthalpy) of sublimation is the amount of energy that must be added to a solid at constant pressure in order to turn it directly into a gas (without passing through the liquid phase).