Transcript Chapter 2
Chapter 2 Matter and Energy Energy Energy—the capacity to do work Where does your energy come from? Can be in the forms: light, heat, chemical, mechanical, electrical, and sound Transfer of Heat Look at your food labels—bomb calorimeter Heat—energy transferred between objects that are at different temperatures Heat is transferred from a warmer to cooler objects Changes in Matter Physical Changes Melting Boiling Cutting Chemical Changes Cooking Baking Burning Change in Energy Evaporation—the changing from a liquid to a gas Energy must be put into the system to surpass the boiling point of a liquid. Energy may be released when going down the phase diagram, that is from vapor to liquid, etc. Endothermic and Exothermic Endothermic Heat is ABSORBED the system EX: melting of ice & boiling of water & cold packs Makes objects feel cooler! Exothermic Heat is RELEASED from the system EX: freezing of water & heat pack & glow sticks Makes objects feel hotter! Law of Conservation of Energy States that energy (E) cannot be created nor destroyed but can be changed from one form to another. The quantity of energy remains the same. E = mc2 Released as heat Worst industrial disaster: Grandcamp in Texas in April 1947. Cargo ship carrying fertilizer Kinetic E—the E of an object that is due to the object’s motion The object is moving! Temperature vs. Heat Temperature—actual measurement of the average kinetic E of the random motion of particles in a substance. A measure of how hot or cold something is. As kinetic E increases, so does the temperature! Heat is the E that is being transferred and temperature is the measurement! How to express temperature Kelvin (K): SI unit for temperature At 0K, absolute zero, all particles cease. K = oC + 273 Celsius (oC): 0oC is the freezing point of water 100oC is the boiling point of water oC = K - 273 Specific Heat The quantity of heat required to raise a unit of mass of homogeneous material 1K or 1oC in a specified way.