What are the molecules of matter doing all the time?! Heat and Temperature! Notes! All matter is composed of continually jiggling atoms or molecules! The jiggling is! If something is vibrating, what kind of energy does it have?! What is temperature?! the energy of motion! Temperature is the quantity that tells you _ with respect to some standard.!
The Celsius ( ) Scale! Temperature at which water freezes (at standard atmospheric pressure)! Temperature at which water boils (at standard atm. Pressure)! 100 equal parts called degrees! Centigrade (100 degrees)! The Fahrenheit Scale! Temperature at which water freezes (at standard atm. Pressure)! Temperature at which water boils (at standard atm. pressure)! Greater precision when reporting temperature with whole numbers since the degrees are smaller! Lord Kelvin! British Physicist! Absolute Zero! 0 Kelvin (0 K)! No kinetic energy! No molecular motion! 0 K = -273 C! Degrees are the same size as Celsius degrees! The Kelvin Scale" (or the SI Scale)! What does temperature really measure?! Random motion of molecules in a substance! per molecule!!
How does a thermometer work?! Matter contains! Measures temperature by means of and of a liquid.! Energy flows until (same temperature) is reached! Small thermometer relative to object so its temperature doesn't drastically change the temperature of the object.! Registers its own temperature! Matter contains (or internal energy)! Heat is the of one thing to another because of a temperature difference.! What is heat?! How do you know the direction of energy transfer between two objects in thermal contact?! Direction of energy transfer is based on! Direction of energy transfer is always from thing to a neighboring thing!
What happens when a substance absorbs or releases thermal energy?! Different things may happen! Increase or decrease in kinetic molecular energy ( )! Phase change (change in the structure of the molecules)! Quantity of Heat! Calorie: the amount of heat required to change the temperature of 1 gram of water by 1 C.! Heat energy can also be measured in Joules! 1 calorie = 4.184 Joules! 1 kilocalorie = 1000 calories = 1 food calorie = 1 Calorie! What is thermal equilibrium?! After objects in thermal contact with each other reach the same temperature, no longer flows between them and we say that the objects are in.! To read a thermometer we wait until thermal equilibrium is reached.! Thermal Expansion! When the temperature of a substance in increased, its molecules and normally tend to move.! Nearly all matter when its temperature increases and when its temperature decreases.! The amount of thermal expansion depends on the.! Different materials expand at different rates.!
Thermal Expansion, cont.! Thermal Expansion, cont.! Bimetallic strips take advantage of different expansion rates. The strips bend when heated. This is used in thermostats! The thermal expansion and contraction of water is quite complicated due to its odd crystalline structure.! Specific Heat Capacity! Some materials (for example foods) remain hot much longer than others.! Different substances have different capacities for storing thermal energy.! Specific Heat Capacity, cont.! We describe a material's ability as its specific heat capacity. Water, for example, has a specific heat capacity because water absorbs heat and only experiences a change in temperature.! The specific heat capacity of any substance is defined as the.!
The high specific heat capacity of water:! Water has a much higher capacity than most common materials. A relatively small amount of water absorbs a great deal of heat for a small temperature rise.! Water is used in cooling systems! Climate effects! Specific Heat Capacity: " The Formula! Q = mc"t Where:! Q = heat ( Quantity of heat)! m = mass! c = specific heat! #T = change in temperature! The c of water! As we have already discussed, water has a fairly high specific heat! The specific heat capacity of water can be expressed as either! c water = 1 cal/(g C) =1 cal/(g" K) The End! or! cwater = 4.184 J/(g C) = 4.184 J/(g" K)