Last weeks topics:Understanding Base Concepts

[1] L. J. Durak and A. Hübler. Scaling of knowledge in random conceptual networks. Lecture Notes in Computer Science 2074, 976-985 (2001).[2] A. Hübler, Understanding Complex Systems: Defining an abstract concept. Complexity 12(5), 5-9(2007).

States of Matter:- Solids (dense, fixed shape)- Liquids (dense)- Gases (not dense)

This week: Temperature and HeatJames scholars honors credit

Temperature

Context: Boiling water is hot. Ice is cold. When it snows, the air is cold.Objective: Describe how hot or cold a material (solid/liquid/gas) is.

-Temperature is a measure for heat content = thermal energy = the energy that can be removed from/added to matter by bringing it in contact with other matter. Transferred thermal energy is called heat.-There is a minimum temperature, where all particles are at rest (0K).- When two materials are in contact, heat flows from the hot to the cold object, and eventually the two materials have the same temperature, no matter what them are made off, no matter if they are solids or fluids.

Definition: Temperature is a measure for hotness and coldness and can be felt and measured with a thermometer. Temperature measures how fast the molecules in a material are moving (vibration and translation)

Latent heat of Vaporization

(boiling)

Latent heat of fusion (melting)

Raising the temperature: melting & boiling

Latent heat of evaporation: the amount of thermal energy that evaporates 1kg (~ 2lbs) of a material at the boiling temperature

Latent heat of fusion: the amount of thermal energy that melts 1kg (~ 2lbs) of a material at the melting temperature

Discussion of temperature continued …

- When heated, most materials melt at the melting temperature, and evaporate at a boiling temperature => used in steam engines (nuclear power plants, coal power plants)

Lecture demo: Large latent heat of water, small latent heat, Hero’ steam engine, Liquid Nitrogen steam engine

Discussion of temperature continued …

-To raise the temperature of a material, thermal energy is required, i.e. heat has to be transferred.

Mixtures: Tcold object < Tboth in contact < Thot object

Example: Water has a very large specific heat, compared to steel, therefore1kg of hot steel + 1 kg of cold water ->warm water + warm steel

Specific heat: the amount of thermal energy that heats 1kg (~2 lbs) of a material by 1K (~2o F)

The flame of a match heats the air.

Discussion of temperature continued …

-When the temperature is raised, most materials expand

=> used for thermometers => used for heat engines (cars)Lecture demos: bimetallic strip ( homemade bimetallic strip ), breaking glass, ball and ring

Commonly used scales are:

but Kelvin is the scientific scale .Normal human body temperature is 36.8 °C ±0.7 °C, or 98.2 °F ±1.3 °F.

A Thermometer in Celsius scale

Thermometers measure the temperature.

Discussion of temperature continued …

-All materials conduct heat, metals conduct heat very wellLecture demo: heat conduction (copper versus wood)

- When heated, most materials change their color, and glow at high temperatures

- When heated, most materials become less stiff

Wireless light bulb?

Temperature

Definitions: -Temperature is a measure for hotness and coldness and can be felt or measured with a thermometer. -Temperature measures how fast the molecules in a material are moving or vibrating-Temperature measures the heat content = thermal energy