ENERGY TRANSFER IN TEMPERATURE INSTRUCTED BY MS SORN

AGENDA DO NOW (ACCESSING PRIOR KNOWLEDGE) DO NOW PT. II RECAP OF COMPREHENSION CHECK NOTEBOOK FORMAT LESSON MINI ACTIVITY COMPREHENSION CHECK

DO NOW – TUESDAY, 3/28 Question: What is the general definition of energy? Answer: The ability to do work or cause change.

ASSIGNED READING: ENERGY TRANSFER IN TEMPERATURE (DO PG. 4) TODAY’S HOMEWORK ASSIGNED READING: ENERGY TRANSFER IN TEMPERATURE (DO PG. 4)

LEARNING TARGET

OBJECTIVES Be able to define and thoroughly explain conservation of energy and energy transfer: The amount of energy transfer needed to change the temperature of a matter sample by a given amount depends on the nature of the matter, the size of the sample, and the environment.

By definition, energy is : the ability to do work or cause change. WHAT IS ENERGY? By definition, energy is : the ability to do work or cause change. a fundamental entity of nature that is transferred between parts of a system in the production of physical change within the system and usually regarded as the capacity for doing work usable power (as heat or electricity); also :  the resources for producing such power

What is thermal energy? By definition, thermal energy is the average kinetic energy of the atoms and molecules of a substance.  Kinetic energy - energy associated with motion The molecules and the motion of atoms create thermal energy, which is present in all matter. 

energy associated with motion What is kinetic energy? energy associated with motion This kinetic energy generates heat, which is measured by temperature that can be transferred within a system.

THERMAL ENERGY A difference in temperature between two locations will cause a flow of heat along a (thermally) conducting path between those two locations. Heat will flow from a hotter object to a cooler object.

Energy Transfer in Temperature Figure 1. Thermal Energy Flow

WHAT IS MATTER? a :  the substance of which a physical object is composed b :  material substance that occupies space, has mass, and is composed predominantly of atoms consisting of protons, neutrons, and electrons, that constitutes the observable universe, and that is interconvertible with energy

WHAT IS AN atom? :  the smallest particle of an element that can exist either alone or in combination

AVERAGE KINETIC ENERGY

CELSIUS VS. FAHRENHEIT Although the SI unit for temperature is the Kelvin (K), laboratory thermometers generally use the Celsius scale to measure temperature.

Transfer of Thermal Energy Heat transfer occurs when two objects or systems are at different temperatures. Energy moves from objects with the higher temperature and into objects with the lower temperature.  The energy cools the former and heats the latter. This transfer happens in three different ways: by conduction within solids; by convection, or the flow of liquid or gas; and by radiation, which can travel across space. 

3 FORMS OF HEAT TRANSFER Figure 2. Model of Heat Transfer

CONDUCTION Conduction is the transfer of heat within solids or when solids are in contact with each other, such as the heating element on a stove that is warming the metal pot above.

CONVECTION Convection is the transfer of heat by the flow of liquid or gas, such as warm ocean currents moving toward cooler ocean currents or when warm air masses move into areas of cooler air masses.

RADIATION For shorter wavelengths (ultraviolet and X-ray), the radiation’s energy is absorbed within the atoms or molecules, which may possibly ionize them by knocking out an electron. Unlike conduction and convection, the transfer of heat by radiation does not need a medium to travel through. The Sun’s radiation warming the Earth is an example. Radiation is the transfer of heat by electromagnetic waves. When matter absorbs light or infrared radiation, the energy of that radiation is transformed into thermal motion of particles

Factors Affecting Thermal Energy Transfer The type of matter involved affects the transfer of thermal energy. Different objects have different thermal properties.

Factors Affecting Thermal Energy Transfer These factors include: 1) Whether the object is an insulator or conductor 2) The amount of matter 3) The surrounding temperature

Factors influencing thermal transfer: INSULATORS VS. CONDUCTORS Insulators: Objects that do not easily transfer thermal energy are called insulators. Wood Thick paper   Conductors: Alternatively, objects that can transfer thermal energy easily are called conductors.  Metal Water Wood, for example, is commonly used as an insulator. Thick paper, which contains wood fibers, can also be used as an insulator. For example, hot coffee from a café might have a paper wrapper around the cup to protect the drinker’s hand from the heat inside. Tiny pockets of air insulate the cup from heat transfer. Objects that are not dense and are non-metal make good insulators. For those reasons, pots have rubberized or wooden handles to prevent the heat from burning one’s hands. Metals are usually good thermal conductors. Their molecules are packed tightly so heat is easily transferred. Water is also a good conductor of heat, but heat energy is rapidly lost when the source is removed. Sand and sidewalk surfaces can become extremely hot on beaches during the summertime because the Sun’s thermal energy is transferred to the exposed surface of Earth.

INSULATORS VS. CONDUCTORS Figure 3. Insulators Figure 4. Conductors

Factors influencing thermal transfer: amount of matter The amount of matter: The transfer of thermal energy is also affected by the amount of matter involved. Pouring a liter of boiling water into a liter of room temperature water will result in a greater temperature change in the, now, two liters of water compared to pouring a liter of boiling water into a tank filled with 50 liters of room temperature water. The greater amount of matter decreases the thermal conductivity of a substance, or it decreases how easily heat can be transferred through the substance.

WHAT IS MATTER? a :  the substance of which a physical object is composed b :  material substance that occupies space, has mass, and is composed predominantly of atoms consisting of protons, neutrons, and electrons, that constitutes the observable universe, and that is interconvertible with energy

AMOUNT OF MATTER Figure 5. Transfer of Thermal Energy

Factors influencing thermal transfer: SURROUNDING TEMPERATURE The environment also affects the transfer of thermal energy between objects. Thermal energy transfers from hotter objects to cooler objects. The temperature of the surrounding environment can affect the transfer of energy. Pouring a liter of boiling water into a liter of room temperature water will result in a greater temperature change in the, now, two liters of water compared to pouring a liter of boiling water into a tank filled with 50 liters of room temperature water. The greater amount of matter decreases the thermal conductivity of a substance, or it decreases how easily heat can be transferred through the substance.

TRANSFER OF THERMAL ENERGY Figure 6. Transfer of Thermal Energy