2 nd Law of Thermodynamics, Entropy, heat calculations Thursday, January 15, 2014 Thursday, 1/15 Respond to the following on your warm-up sheet Describe the first law of thermodynamics and give a real world example of the law. Upcoming dates: Thursday, 1/22 Thermodynamics quiz Monday, 1/26 Thermodynamics test Monday, 1/26 Thermodynamics project due (15 minutes after the bell rings). Thursday, 2/5 Waves Quiz Friday, 2/6 4SW extra credit due by 4:00 PM Friday, 2/13 Waves Quiz Friday, 2/13 End of 4SW Wednesday, 2/18 Waves Test (5SW) Notes - Entropy Review the following slides and add to your notes. Processes in nature Types of processes Reversible is a process that after its finished can go backwards and end up where it started. Irreversible is a process that cannot go back and restore itself All processes that occur in nature are irreversible (ex. a flower pot is dropped and shatters on the ground the pot cannot be restored to its original state on its own). Entropy Is a measure of disorder of a system Diagram source cnx.orgcnx.org Entropy Relating entropy to different states of matter When a substance is in a gas stage theres more disorder than there is in a liquid stage because the molecules are held closer together in a liquid form. When a substance is in a liquid stage theres more disorder than there is in a solid stage because the molecules are held closer together in a solid stage. Diagram sources www2.ucdsb.on.ca Diagram sources www2.ucdsb.on.ca and cnx.org cnx.org Restating the 2 nd Law of Thermodynamics Natural processes tend to move toward a state of greater entropy. Notes - specific heat, measuring heat energy Review the following slides and add to your notes. Lets think Do you think all substances/objects gain and lose heat at the same rate? Tell your elbow partner your thoughts and explain your position. What is specific heat? Every substance gains or loses heat based on its identity/physical property. The physical property of a substance is its specific heat capacity. Examples of specific heat What is specific heat capacity? Is the amount of heat (thermal energy) required to raise a unit of mass of the substance by one degree of temperature (liquids and solids). Measure of how much thermal energy is required to change the temperature of a substance. What is the equation for calculating heat change How do you determine if heat is gained or lost If heat energy is gained Q is positive. If heat energy is lost Q is negative. Example problem