Temperature, heat, and expansion Temperature is a quantity that tells us how hot or cold something is compared to a standard. Temperature is measured using a thermometer. It is a device that takes advantage of the fact that most substances expand when heated and contract when cooled.

Temperature, heat, and expansion A thermometer consists of a thin glass tube containing a liquid such as mercury or alcohol. The tube has a scale that indicates the temperature

Temperature, heat, and expansion A thermometer consists of a thin glass tube containing a liquid such as mercury or alcohol. Celsius scale - water freezes at 0° and boils at 100°. Fahrenheit scale – water freezes at 32° and boils at 212°.

Temperature, heat, and expansion Kelvin scale – its degrees are the same size as the Celsius scale, but it zero is the lowest possible temperature called absolute zero Absolute zero corresponds to -273°C

Temperature Heat is energy being transferred from material at a higher temperature to material at a lower temperature. Once the energy is transferred it is no longer heat, but becomes part of the internal energy of the receiving material

Temperature, heat, and expansion Temperature is related to the motion of molecules in a substance. It is closely related to the average kinetic energy of the molecules. It is not a measure of the total kinetic energy of the molecules

Temperature, heat, and expansion If heat is able to flow between materials, we say that the materials are in thermal contact. When two or more materials in thermal contact are at the same temperature, we say that they are in thermal equilibrium. Heat will not flow between them.

Temperature, heat, and expansion The molecules in materials contain energy in various forms both potential and kinetic. The grand total of these energies is called the internal energy of the substance.

Temperature, heat, and expansion Various units are used to measure heat. The textbook works primarily with calories (cal) and kilocalories (kcal)(C). We will be working primarily with joules(J). 1 calorie= 4.186J 1 kilocalorie (C)= 1000 calories

Temperature, heat, and expansion Specific heat capacity (or specific heat) is the amount of heat required to raise the temperature of a unit mass of material by 1 degree celsius.

Temperature, heat, and expansion Specific heat capacity (or specific heat) is the amount of heat required to raise the temperature of a unit mass of material by 1 degree Celsius.

Temperature, heat, and expansion Relationships between specific heat, mass, heat, and change in temperature.

Temperature, heat, and expansion Relationships between specific heat, mass, heat, and change in temperature.

Temperature, heat, and expansion Relationships between specific heat, mass, heat, and change in temperature.

Temperature, heat, and expansion Relationships between specific heat, mass, heat, and change in temperature.

Temperature, heat, and expansion Relationships between specific heat, mass, heat, and change in temperature.

Temperature, heat, and expansion Water has a higher specific heat than most materials because its molecules can absorb a great deal of energy into motions that do not contribute to temperature change, such as rotation, internal vibration, and bond stretching.

Temperature, heat, and expansion Thermal expansion is the tendency of matter to change in volume in response to a change in temperature. Different materials expand and contract at different rates.

Temperature, heat, and expansion Thermal expansion is utilized in devices such as thermostats, and dial thermometers. A bimetallic strip consisting of two metal strips fused together will bend in a way that is proportional to the chnge in temperature.

Temperature, heat, and expansion This motion can open or close a switch, or move a thermometer needle. Other examples of the role of thermal expansion are on pages 316 and 317.

Temperature, heat, and expansion When cooled from room temperature liquid water becomes increasingly dense, as with other substances, but at approximately 4 °C pure water reaches its maximum density. As it is cooled further, it expands to become less dense. This unusual negative thermal expansion is explained by the formation of microscopic ice crystals.

Temperature, heat, and expansion Ice (solid water) is less dense than liquid water. This is a result of the open structured arrangement of the water molecules in the solid state (page 320).

Temperature, heat, and expansion As a result ice floats on top of liquid water. When large bodies of water begin to freeze, ice forms an insulating layer on top of the water, thereby preventing the water below from freezing (page 321).