Chapter 10 Heat and Temperature Define temperature? A measure of the average kinetic energy of all the particles within an object. What happens if the kinetic energy of an object increases? The temperature increases What physical property of substances allows us to measure temperature accurately? Objects expand when their temperature increases
What device is used to measure temperature? Thermometer How does a thermometer work? As the temperature rises- particles inside the thermometer gain kinetic energy and move faster, which causes the particles in the liquid to move farther apart causing it to expand and rise up the tube. What is absolute zero? Temperature at which particles no longer have any energy that can be transferred.
What is heat? Energy transfer when two objects at different temperatures interact with one another How do you get burned? Rapid tranfer of energy as heat Can you get burned from something cold? Yes….when you touch a very cold object, energy transfers as heat from your skin into the object causing tissue damage.
What are the three ways that energy can be transferred? CONDUCTION: OBJECTS IN DIRECT CONTACT WILL HAVE TRANSFER OF ENERGY AS HEAT EXAMPLE: POT ON STOVE CONVECTION: TRANSFER OF ENERGY BY MOVEMENT OF WARM FLUIDS: OVEN RADIATION:NO DIRECT CONTACT, DOESN’T INVOLVE THE MOVEMENT OF MATTER-TRANFER OF ENERGY BY ELECTROMAGNETIC WAVES: SUN LIGHT
How does conduction work? Before conduction: the average kinetic energy of particles in an object is the same throughout During conduction: the energy is transferred from objects to slowly moving particlesnearby.
How does Convection Work? During convection, energy is carried away by a heated gas or liquid that expands and rises above cooler, denser gas or liquid. The rising warm air is replaced by cooler, denser air, which becomes hot and expands and rises unit it cools contracts, becomes denser, and sinks Does convection occur within solids? No because particles within solids are not free to move.
How does radiation work? • Radiation occurs through electromagnetic waves in the form of infrared radiation, visible light, and ultraviolet rays. • Radiation is the only method of energy transfer that can take place in a vacuum
What is the difference between conductors and insulators? Conductors transfer energy as heat quickly Solids conduct energy better than liquids or gas because their particles are packed closely together. An exception to liquids as conductors would be molten or liquid metals which are good. Metals are better conductors than nonmetals. Insulators slow the transfer of energy as heat. Wood is a good insulator
What is specific heat? Describes how much energy is required to raise an objects temperature. Is the amount of energy transferred as heat that will raise the temperature of 1 kg of a substance by 1 K. Why do we need to know the specific heat of a substance? Predict the effects of larger temperature changes for masses other that 1 kg
What is the equation for specific heat? Energy = (specific heat) x (mass) x (temp ch.) Energy= cm∆t
What are 2 principles of thermodynamics? • 1st law: Conservation of energy the total energy used in any process is conserved 2. 2nd law: Energy transferred as heat always moves from an object at a high temperature to an object at low temperature.