Temperature

Celsius & Kelvin Temperature Scales 100 Kelvins 373 K 273 K 0 K Boiling point of water 100oC 100 Celsius degrees Freezing point of water 0oC Students need to realize that the Celsius scale is based on the Kelvin scale. 1o Celsius and 1 Kelvin are equal size units It is not possible to have a temperature below 0 Kelvin (absolute zero). Absolute zero -273oC

Temperature is Average Kinetic Energy “HOT” “COLD” Average Kinetic Energy is temperature. Mathematically, kinetic energy (avg) = ½ mv2. Total kinetic energy is what we call heat. Heat is measured with an instrument called a calorimeter. Temperature is measured with an instrument called a thermometer. Fast Slow Kinetic Energy (KE) = ½ m v 2 *Vector = gives direction and magnitude

Temperature Scales Fahrenheit 212 oF 180 oF 32 oF Celcius 100 oC 0 oC Kelvin 373 K 100 K 273 K Boiling point of water An absolute English scale exists called the Rankin scale. On the Kelvin scale it is NOT possible to have a negative temperature. Daniel Gabriel Fahrenheit (1686-1736), German physicist invented mercury thermometer in 1724 ice bath with salt = 0oF body temperature =96oF freezing point (of water) = 32oF boiling point (of water) = 212oF Anders Celsius (1701-1744), Swedish astronomer modified mercury thermometer in 1742 freezing point (of water) = 0oC boiling point (of water) = 100oC A Celsius degree is also called a centigrade. William Thomson (1824-1907), English physicist knighted Lord Kelvin in 1848 proposed a scale based on lowest possible temperature freezing point (of water) = 273 K boiling point (of water) = 373 K coldest possible temperature = 0 K or absolute zero = -273.15oC Freezing point of water Notice that 1 kelvin degree = 1 degree Celcius

Kelvin Scale blue 5250 K Sunlight 5000 K PIAA Plasma Blue white yellow 4300 K PIAA HID Bulb 5000 K PIAA Plasma Blue 5250 K Sunlight 4150 K PIAA Xtreme White 3800 K PIAA Super White 3200 K Halogen Bulb 2600 K Incandescent Bulb

Temperature Scales An absolute English scale exists called the Rankin scale. On the Kelvin scale it is NOT possible to have a negative temperature. Daniel Gabriel Fahrenheit (1686-1736), German physicist invented mercury thermometer in 1724 ice bath with salt = 0oF body temperature =96oF freezing point (of water) = 32oF boiling point (of water) = 212oF Anders Celsius (1701-1744), Swedish astronomer modified mercury thermometer in 1742 freezing point (of water) = 0oC boiling point (of water) = 100oC A Celsius degree is also called a centigrade. William Thomson (1824-1907), English physicist knighted Lord Kelvin in 1848 proposed a scale based on lowest possible temperature freezing point (of water) = 273 K boiling point (of water) = 373 K coldest possible temperature = 0 K or absolute zero = -273.15oC Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 136

Compare Celsius to Fahrenheit oF – 32 = 1.8 oC Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 139

Converting 70 degrees Celsius to Kelvin units. oC + 273 = K Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 137

Temperature Scales Temperature can be subjective and so fixed scales had to be introduced. The boiling point and freezing point of water are two such points. Celsius scale (oC) The Celsius scale divides the range from freezing to boiling into 100 divisions. Original scale had freezing as 100 and boiling as 0. Today freezing is 0 oC and boiling is 100 oC. Fahrenheit scale (oF) Mercury and alcohol thermometers rely on thermal expansion Anders Celsius (1701 - 1744) Lord Kelvin (William Thomson) 1824 - 1907 Daniel Gabriel Fahrenheit (1686-1736) Daniel Gabriel Fahrenheit (1686-1736), German physicist invented mercury thermometer in 1724 ice bath with salt = 0oF body temperature =96oF freezing point (of water) = 32oF boiling point (of water) = 212oF Anders Celsius (1701-1744), Swedish astronomer modified mercury thermometer in 1742 freezing point (of water) = 0oC boiling point (of water) = 100oC A Celsius degree is also called a centigrade. William Thomson (1824-1907), English physicist knighted Lord Kelvin in 1848 proposed a scale based on lowest possible temperature freezing point (of water) = 273 K boiling point (of water) = 373 K coldest possible temperature = 0 K or absolute zero = -273.15oC

Thermal Expansion Most objects e-x-p-a-n-d when heated Large structures such as bridges must be built to leave room for thermal expansion All features expand together Cracks in sidewalk. COLD HOT

Equal Masses of Hot and Cold Water Thin metal wall Insulated box Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 291

Water Molecules in Hot and Cold Water Hot water Cold Water 90 oC 10 oC Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 291

Water Molecules in the same temperature water (50 oC) Water (50 oC) Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 291

Heat versus Temperature lower temperature higher temperature Fractions of particles TOTAL Kinetic ENERGY = Heat Kinetic energy

Molecular Velocities the Maxwell speed distribution molecules sorted by speed many different molecular speeds Fractions of particles the Maxwell speed distribution speed http://antoine.frostburg.edu/chem/senese/101/gases/slides/sld016.htm

Temperature vs. Heat Different Alike Different Topic Topic Have Kinetic Energy Measured with a Thermometer Measured with a Calorimeter Topic Topic Average Kinetic Energy A Property of Matter Total Kinetic Energy Heat Temperature Melting point and boiling point are both INTENSIVE properties of matter (related to temperature) Heat is an EXTENSIVE property of matter (the more wood you burn...the more heat is produced) oCelcius (or Kelvin) Joules (calories)

Conservation of Matter Conservation of Matter: Matter can neither be created nor destroyed. Atoms rearrange in chemical reactions – the macroscopic (what we see) view of things may appear as though ‘new’ matter has been created. However, at the microscopic level we would see only that compounds and molecules have been broken apart and rearranged into new compounds and molecules (from the same atoms we started with). This is a demonstration using potassium iodide mixed with lead nitrate to yield a precipitate of lead (II) iodide and soluble potassium nitrate. A small test tube filled with lead nitrate is resting inside the Erlenmeyer flask. When inverted, the chemical reaction occurs. No new material is added to the flask - it is a closed system. During the chemical reaction, atoms are rearranged. The product has different properties (i.e. it changes from colorless to yellow) than the reactants. Lead (II) iodide is very toxic. Dispose of waste in a responsible manner. Lead (II) iodide is also the pigment added to road stripe paint. Reactants yield Products

Heavy Metal Poisoning TREATMENT: Chelation therapy EDTA (ethylenediamine tetra acetic acid) Exposure to mercury made the Hatter “mad”. Look for links to web sites for more information: Chelation therapy Toxicity of heavy metals Lead is no longer added to house paint. Green-treated wood no longer uses arsenic and is now labeled AC-2 (second generation without arsenic). EDTA is added as a preservative to canned foods to remove any extra metal ions present. Arsenic treated lumber. ‘Green-treated’ wood will not rot outdoors for 50 years. Eating chips of lead paint causes brain damage.

World of Chemistry The Annenberg Film Series VIDEO ON DEMAND Episode 5 – A Matter of State Matter is examined in its three principal states – gases, liquids, and solids – relating the visible world to the submicroscopic world that cannot be seen. This program reveals, at the molecular level, how changes in matter occur, enlarging the idea of models from the previous program. (Running Time: 28:38) VIDEO ON DEMAND Episode 13 – Driving Forces Why doe chemical reactions occur and what controls their speeds? Endothermic and exothermic reactions are investigated and the role of entropy is revealed. (Running Time: 28:40) Video 05: Matter of State Matter is examined in its three principal states — gases, liquids, and solids — relating the visible world to the submicroscopic. (added 2006/10/08) World of Chemistry > http://www.learner.org/vod/vod_window.html?pid=797 Video 13: Driving Forces Endothermic and exothermic reactions are investigated and the role of entropy is revealed. (added 2006/10/08) World of Chemistry > http://www.learner.org/vod/vod_window.html?pid=805 Video 19: Metals Malleability, ductility, and conductivity are examined, along with methods for extracting metals from ores and blending alloys. (added 2006/10/08) World of Chemistry > http://www.learner.org/vod/vod_window.html?pid=811 Journey through the exciting world of chemistry with Nobel laureate Roald Hoffman as your guide. The foundations of chemical structures and their behavior are explored through computer animation, demonstrations, and on-site footage at working industrial and research labs. Distinguished scientists discuss yesterday’s breakthroughs and today’s challenged.   Produced by the University of Maryland and the Educational Film Center. Released on cassette: Fall 1989 The Annenberg/ / CPB Collection 1-800-LEARNER VIDEO ON DEMAND Episode 19 – Metals The important properties of metals – malleability, ductility, and conductivity – are examined. The methods used to extract metals from ores and to blend metals to form alloys with improved physical characteristics are covered. (Running Time: 28:36)