Notes

ESL
Page 164
Exs 13,15,23,31
read all charts

As a class, what are some things you have to do after class today?
Before going to bed tonight, what do you have to do? Is there any place you have to go later today?
In everyday life, what are some things that you must have in order to survive?
Looking ahead to the next week, what are some things that you have to do?
Last week, what were some things that you had to do?
In the job of a doctor, what kinds of things must they know about? What are some tasks that a doctor has to do on a daily basis?

Physics
Heat
kinetic molecular theory

- All matter is made up of small constantly moving particles
- Particles exerts force on each other and are on average far apart (relative their diameter)
- The three states of matter are due to the distance b/w particles and the strength of the force of attraction b/w them

Heat -> Thermal energy transfer

- Thermal energy: the total energy (potential and kinetic) of all particles in a object
- Heat: energy that is transferred from one body to another because of a difference in temperature
- Temperature: a measure of the average kinetic energy of individual particles

Temperature Scales

- Temperature: measure of average kinetic energy of the particles in a substance
- Celsius Scale - based on boiling point (100°) and freezing point (0°) of water
- Fahrenheit scale - based on boiling point freezing point of salt-water °c temp = °f temp -32) * 5/9
-Kelvin Scale - based on absolute zero (no motion in the particles of a substance)

Absolute Zero & the kelvin Scale

- The Kelvin scale is setup so that its zero point is the coldest possible temperature absolute zero, at which point a substance would have zero internal energy. This is 273.15 °C, or -459.69 °F. Absolute zero can never be reached, but there is no limit to how close we can get to it. Scientists have cooled substances to within 10-5 kelvins of absolute zero. How do we know how cold absolute zero is, if nothing has ever been at that temperature? The answer is by graphing Pressure vs. Temperature for a variety of gases and extrapolating.

Thermal Equilibrium

Two bodies are said to be at thermal equilibrium if they are at the same temperature. This means there is no net exchange of thermal energy b/w the two bodies. The top pair of objects are in contact, but since they are at different temps, they are not in thermal equilibrium, and energy is flowing from the hot side to the cold side.

HOT ---heat ---> cold
26 °C 26 °C
no heat flow

Methods of heat transfer
Methods of heat transfer: conduction, convection, radiation.
Convection

-Heat is transferred by the circulation of a fluid (liquid or gas) over relatively large distances






Homework
- Read p 270-274
- P 274 # 1,2,4
- Read p 275-280
- P 280 # 1-5

Page 270 - 280

Warmth and coldness

In physics, "warmth" and "coldness" refer to the relative temperature of objects or substances. Temperature is a measure of the average kinetic energy of the particles in a system, and is often measured in units of degrees Celsius (°C) or Kelvin (K).

An object or substance with a higher temperature is considered "warmer" than one with a lower temperature. Conversely, an object or substance with a lower temperature is considered "colder" than one with a higher temperature.

Heat energy can flow spontaneously from a warmer object to a cooler object, a process known as heat transfer. This transfer continues until the two objects reach thermal equilibrium, meaning they have the same temperature.

Understanding warmth and coldness is important in many areas of physics, including thermodynamics, which studies the relationship between heat, temperature, and energy.

How is produced

- Warmth and coldness in physics are produced by the transfer of heat energy between objects or substances. Heat energy is a form of energy that is transferred from one object or substance to another due to a temperature difference.

- Heat transfer can occur through several mechanisms such as conduction, convection, and radiation. In conduction, heat is transferred through a material or between materials that are in direct contact with each other. In convection, heat is transferred through the movement of fluids, such as air or water. In radiation, heat is transferred through electromagnetic waves.

- For example, when you place your hand on a hot stove, heat is transferred from the stove to your hand through conduction. Similarly, when you turn on a heater in a room, heat is transferred from the heater to the air in the room through convection.

- In addition, heat can be produced through various physical and chemical processes, such as combustion or nuclear reactions. For example, the warmth from a fire is produced through the combustion of wood, while the warmth from the sun is produced through nuclear reactions in its core.

- Overall, warmth and coldness in physics are produced by the transfer and generation of heat energy through various mechanisms and processes.

Thermal Energy

- Thermal energy refers to the energy that is present in a substance due to the movement of its particles, which can include atoms, molecules, and ions. It is a form of kinetic energy that arises from the random motion of these particles, which can cause them to collide and transfer energy between each other. The more rapidly these particles are moving, the greater the amount of thermal energy present in the substance. Thermal energy is typically measured in units of joules (J) or calories (cal), and is closely related to temperature. In fact, the temperature of a substance is a measure of the average kinetic energy of its particles. Thermal energy plays a crucial role in many areas of physics and engineering, including thermodynamics, heat transfer, and energy conversion.

Difference between Thermal Energy and Heat

Thermal energy and heat are related concepts, but they are not the same thing. Thermal energy is the total amount of energy that is present in a substance due to the movement of its particles. Heat, on the other hand, is the transfer of thermal energy between objects or substances due to a temperature difference.

In other words, thermal energy refers to the energy contained within a substance, while heat refers to the transfer of that energy from one substance to another. Heat is a form of energy transfer, whereas thermal energy is a form of energy that can be transferred.

For example, if you place a hot object in contact with a cooler object, heat will flow from the hotter object to the cooler object until they reach the same temperature. This transfer of heat is due to the difference in thermal energy between the two objects. The hotter object has more thermal energy than the cooler object, and so heat flows from the hotter object to the cooler object.

Methods to Transfer Thermal Energy

There are three main methods by which thermal energy can be transferred between objects or substances: conduction, convection, and radiation.

1. Conduction: This is the transfer of thermal energy between objects or substances that are in direct contact with each other. The heat is transferred through the collisions of the particles in the materials. Materials that conduct heat well, such as metals, transfer thermal energy quickly, while materials that are poor conductors, such as plastics, transfer thermal energy slowly.

2. Convection: This is the transfer of thermal energy through the movement of fluids, such as gases or liquids. As the fluid moves, it carries thermal energy with it. For example, when you heat a pot of water on a stove, the heat is transferred through conduction from the stove to the pot, and then through convection as the water in the pot heats up and rises.

3. Radiation: This is the transfer of thermal energy through electromagnetic waves. Unlike conduction and convection, radiation does not require a medium to transfer energy. For example, the warmth you feel from the sun is due to the transfer of thermal energy through radiation.

In addition to these three methods, thermal energy can also be transferred through phase changes, such as melting or boiling, and through chemical reactions, such as combustion.