Transcript Heat and Temperature
Heat and Temperature
Notes
What are the molecules of matter doing all the time?
All matter is composed of continually jiggling atoms or molecules The jiggling is random motion.
If something is vibrating, what kind of energy does it have?
the energy of motion
What is temperature?
Temperature is the quantity that tells you how warm or cold an object is with respect to some standard.
The Celsius (Centigrade) Scale
0º C Temperature at which water freezes (at standard atmospheric pressure) 100 º C Temperature at which water boils (at standard atm. Pressure) 100 equal parts called degrees Centigrade (100 degrees)
The Fahrenheit Scale
32 º F Temperature at which water freezes (at standard atm. Pressure) 212 º F Temperature at which water boils (at standard atm. pressure) Greater precision when reporting temperature with whole numbers since the degrees are smaller
The Kelvin Scale (or the SI Scale)
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
What does temperature really measure?
Random motion of molecules in a substance Average kinetic energy per molecule
How does a thermometer work?
Measures temperature by means of expansion and contraction of a liquid.
Energy flows until thermal equilibrium (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…
Matter contains thermal energy (or internal energy
What is heat?
Heat is the transfer of thermal energy of one thing to another because of a temperature difference.
How do you know the direction of energy transfer between two objects in thermal contact?
Direction of energy transfer is based on temperature Direction of energy transfer is always from a warmer thing to a neighboring cooler thing
What happens when a substance absorbs or releases thermal energy?
Different things may happen Increase or decrease in kinetic molecular energy (temperature change) Phase change (change in the structure of the molecules)
What is thermal equilibrium?
After objects in thermal contact with each other reach the same temperature, heat no longer flows between them and we say that the objects are in thermal equilibrium.