Physical Science – Temperature and Heat

Physical Science – Temperature and Heat Critical Thinking Question: Is there a difference between heat and temperature? To truly understand this relationship you must know about matter!!!!! 1. What is matter? - Made up of particles so small that you can’t see them - Do you remember the kinetic theory of matter? a. All matter is made up of constantly moving particles b. The state of matter is dependent on temperature Review: What are the 3 states of matter? a. Solid b. Liquid c. Gas 2. What is Temperature? It is the measure of the average kinetic energy of the particles in a sample of matter a. What does that mean? Since the particles that make up matter are always moving they have kinetic energy. Temperature is just the measure of that kinetic energy. b. What is hot and cold temperature? - Hot and cold are relative terms that are associated with an increased or decreased kinetic energy - If you have a decreased kinetic energy you temperature is said to be cold and if you have an increased kinetic energy you have a warmer temperature 3. Thermal Energy a. Questions: What happens when you put a cold piece of metal on an ice cube? Answer: Nothing What happens if you put a hot piece of metal on an ice cube? Answer: The ice cube melts Why does nothing happen with the cold metal and the ice cube but something does happen with the hot metal and ice cube? Answer: Thermal Energy – Total energy (both kinetic and potential) of the particles in a material *Remember the law of conservation of energy – energy cannot be destroyed or created under ordinary conditions, only transferred or changed form. In terms of the cold metal and ice cube very little thermal energy is transferred from one object to the next because the kinetic energy is very low in each object. However in the hot metal the kinetic energy is much greater than in the ice cube so the greater energy will be transferred to the object with less energy. Question: What would happen if you added a second piece of hot metal to the ice cube? Answer: You would melt twice as much. Why: By adding a second piece of matter you have doubled the mass of the metal which means it will have twice as much thermal energy. b. Do all objects have the same thermal energies when the mass and temperature are the same? - No!!!! - Experiment – Sand vs Water - Which one did the temperature have a greater effect on? The water! Why – Remember sand is a solid and water is a liquid. Solids are held more tightly together so the kinetic energy of the particles in sand are not as great as in water. Because the particles are not held as tightly in water it is easier to increase the kinetic energy of the particles that make up the water than the sand. *Note: The kinetic energy of the object itself has no effect on its thermal energy. It is the kinetic energy of the particles that make up the object that have the effect on the thermal energy. C. Heat: is the thermal (or internal) energy that flows from something with a higher temperature to something with a lower temperature. - What happens if you pressed your left hand against a cool tile? Answer: Your hand would feel cooler – the temperature decreased - What would happen if you pressed your right hand against the same spot on the tile? Answer: The spot would not feel as cold because of the heat transfer from the left hand warming up the tile - Heat is measured in Joules just like Work and involved the transfer of energy a. Heat – energy transferred between objects at different temperatures b. Work – energy transferred when force acts over a distance Back to the initial question: Is there a difference between heat and temperature? Answer: Yes – temperature is the measure of the amount kinetic energy in an object and heat is the measure of thermal energy that flows from an object of a higher temperature to an object with a lower temperature