M6 Phy 1stSem Finals Section 1,2 thermal eq , defining heat

Chapter II: Heat and Gases

​​Temperature and Thermal Equilibrium

Objectives:

• Relate temperature to the kinetic energy of atoms and molecules.

• Describe the changes in the temperatures of two objects reaching thermal equilibrium.

• Identify the various temperature scales, and convert from one scale to another.

Temperature is proportional to the kinetic energy of atoms and molecules.
The temperature of a substance is proportional to the average kinetic energy of particles in the substance. A substance’s temperature increases as a direct result of added energy being distributed among the particles of the substance.

​Temperature is a measure of the average kinetic energy of the particles in a substance.

Internal energy is the energy of a substance due to both the random motions of its particles and the potential energy that results from the distances and alignments between the particles.

The energies associated with atomic motion are referred to as internal energy, which is proportional to the substance’s temperature (assuming no phase change).

For an ideal gas, the internal energy depends only on the temperature of the gas. For nonideal gases, as well as for liquids and solids, other properties contribute to the internal energy.

The symbol U stands for internal energy, and ∆U stands for a change in internal energy.

Thermal equilibrium is the state in which two bodies in physical contact with each other have identical temperatures. Thermal equilibrium is the basis for measuring temperature with thermometers. By placing a thermometer in contact with an object and waiting until the column of liquid in the thermometer stops rising or falling, you can find the temperature of the object.

​Matter expands as its temperature increases.
Increasing the temperature of a gas at constant pressure causes the volume of the gas to increase. This increase occurs not only for gases, but also for liquids and solids. In general, if the temperature of a substance increases, so does its volume. This phenomenon is known as thermal expansion.


Different substances undergo different amounts of expansion for a given temperature change. The thermal expansion characteristics of a material are indicated by a quantity called the coefficient of volume expansion. Gases have the largest values for this coefficient. Liquids have much smaller values.

Temperature units depend on the scale used.
The temperature scales most widely used today are the Fahrenheit, Celsius, and Kelvin scales.

The graph shows the relationship of pressure versus temperature for an ideal gas at a constant volume. The graph shows that as the temperature of the gas goes down, so does its pressure. If the temperature could drop to -273.15°C, the gas's pressure would be zero. This temperature is called 0.00 K on the Kelvin.

​What are the equivalent Celsius and Kelvin temperatures of 50.0°F?

Activity

The lowest outdoor temperature ever recorded on Earth is −128.6°F, recorded at Vostok Station, Antarctica, in 1983. What is this temperature on the following:
1.Celsius scale
2.Kelvin scale

Multiple Choice

The temperature of a substance is __________ to the average kinetic energy of particles in the substance.

• not proportional

• direct

• proportional

• none of these

Multiple Choice

A substance’s temperature increases as a direct result of added _______ being distributed among the particles of the substance.

• energy

• temperature

• thermal equilibrium

• none of these

Multiple Choice

___________ is the state in which two bodies in physical contact with each other have identical temperatures.

• energy

• temperature

• thermal equilibrium

• none of these

Multiple Choice

Increasing the temperature of a gas at constant pressure causes the _______ of the gas to increase.

• energy

• temperature

• pressure

• volume

Multiple Choice

In general, if the temperature of a substance increases, so does its volume. What phenomenon is this?

• Thermal expansion

• Volume expansion

• pressure

• volume

Multiple Choice

The thermal expansion characteristics of a material are indicated by a quantity called _________.

• thermal expansion

• volume expansion

• coefficient of volume expansion.

• volume

Multiple Choice

It is the energy of a substance due to both the random motions of its particles and to the potential energy that results from the distances and alignments between the particles.

• Internal Energy

• Kinetic Energy

• Ideal gas

• volume

Multiple Choice

What is the symbol used for internal energy?

• K

• I

• U

• IE

​​Defining
Heat

Objectives:

• Explain heat as the energy transferred between substances that are at different temperatures.

• Relate heat and temperature change on the macroscopic level to particle motion on the microscopic level.

• Apply the principle of energy conservation to calculate changes in potential, kinetic, and internal energy.

​​As the bottle of juice cools down, the water’s temperature goes up a little until both the juice and water reach the same temperature. Energy moves from the juice to the water because they start at different temperatures. This movement of energy is called heat.

​What happens when you immerse a warm fruit juice bottle in a container of ice water?

Heat is the energy transferred between objects because of a difference in their temperatures.

Energy is transferred between substances as heat. From a macroscopic viewpoint, energy transferred as heat tends to move from an object at a higher temperature to an object at a lower temperature.

​Transfer of Particles’ Kinetic Energy as Heat Energy is transferred as heat from the higher-energy particles to lower-energy particles (a). The net energy transferred is zero when thermal equilibrium is reached (b).

The transfer of energy as heat alters an object’s temperature.

Thermal equilibrium happens when two objects at the same temperature exchange energy equally, so no net energy is transferred between them. This shows the difference between temperature and heat: temperature measures the energy in an object, while heat is the energy that moves from one object to another due to a temperature difference. When there’s no temperature difference, no heat is transferred. The bigger the temperature difference between two objects, the faster the energy transfers as heat.

Heat is measured in units of energy. Before scientists understood heat as energy, different units were developed to measure it, and many are still in use today. However, all heat units can be converted to joules, the standard unit of energy. Like other forms of energy (e.g., PE for potential energy), heat is represented by the symbol Q.

​

Multiple Select

Heat flow happens in three different ways, which are through

• conduction

• convection

• radiation

• boiling

Multiple Choice

The process of heat transfer from hotter regions to colder regions through a solid medium

• conduction

• convection

• radiation

Multiple Choice

Heat is transferred by the movement of fluid (liquid and gas) from hotter regions to colder regions.

• conduction

• convection

• radiation

Multiple Choice

The formation of land breeze and sea breeze are examples of a

• conduction process

• convection process

• radiation process

Multiple Choice

During the day, we will have

• sea breeze

• land breeze

Multiple Choice

During sea breeze,

• the wind move from sea to land

• the wind move from land to sea

Multiple Choice

During land breeze,

• the wind move from sea to land

• the wind move from land to sea

Multiple Choice

What type of thermal energy transfer is number 1 pointing to?

• Convection

• Conduction

• Radiation

• Insulation

Multiple Choice

What type of thermal energy transfer is number 2 pointing to?

• Convection

• Conduction

• Radiation

• Insulation

Multiple Choice

What type of thermal energy transfer is number 3 pointing to?

• Convection

• Conduction

• Radiation

• Insulation

Multiple Choice

The condition where two substances in physical contact with each other exchange no heat energy. They are said to be the same temperature.

• Thermal Energy

• Cooler to Warmer

• Energy Transfer

• Thermal Equilibrium

Multiple Choice

heat always travels from _____ to ______ objects

• hot to cold
• cold to hot
• cold to cold
• hot to hot

Multiple Choice

You leave your cold spoon in a hot bowl of oatmeal. What happens after an hour?

• The temperature of both the oatmeal and the spoon stay the same

• The spoon and the oatmeal become the same temperature

• Only the temperature of the oatmeal will change

• Only the temperature of the spoon will change

Multiple Choice

If you burn your hand on the handle of a hot pot, heat was transferred to your skin by

• conduction

• convection

• radiation

• equilibrium

Multiple Choice

You are walking to school and find a metal earring in the snow. You take the cold earring inside and place it on your desk. What will happen after a while?

• The earring will be colder than the desk

• The earring and the desk will be colder than room temperature

• The desk will be colder than room temperature

• Both the earring and the desk will be at room temperature

Multiple Choice

Johnny put ice in his water. Which idea do you think best explains why the water got cold?

• The coldness from the ice moved into the water

• The coldness and the heat moved back and forth until the water cooled off.

• The heat from the water moved into the ice.

• The water does not cool of

Multiple Choice

The liquid in a thermometer ______________ as the temperature increases.

• expands
• disappears
• freezes
• explodes

Multiple Choice

Which of the following is NOT true about heat? 

• Heat moves from hot to cold
• Heat is a form of energy
• Heat cannot be transferred
• Heat makes molecules speed up