Section 10.1 Energy, Temperature, and Heat Thermochemistry

Section 10.1 Energy, Temperature, and Heat 1.To understand the importance and general properties of energy 2.To understand the concepts of temperature and heat 3.To understand the direction of energy flow as heat Objectives

Section 10.1 Energy, Temperature, and Heat

Section 10.1 Energy, Temperature, and Heat What is Energy? Kinetic, potential, thermal, gravitational, sound, elastic, light / electromagnetic, electrical, electrostatic energies are examples Energy is the driver of all changes. It flows between objects, it spreads out throughout the universe and in doing so is the driver of all observable phenomena (including chemical reactions)

Section 10.1 Energy, Temperature, and Heat Energy is the ability to do work or produce heat. A. The Nature of Energy Crane Lifting Doing Work: Explosion Producing Heat:

Section 10.1 Energy, Temperature, and Heat What is the difference between potential and kinetic energy?

Section 10.1 Energy, Temperature, and Heat Energy is the ability to do work or produce heat. Potential energy Energy of position Kinetic energy Energy of motion E = ½ mv 2 A. The Nature of Energy

Section 10.1 Energy, Temperature, and Heat A. The Nature of Energy Law of conservation of energy –Energy cannot be created or destroyed, only converted Bounce Ball Into Space

Section 10.1 Energy, Temperature, and Heat A. The Nature of Energy Law of conservation of energy in a chemical reaction –Energy can be converted from one form to another but can neither be created or destroyed. –Stored chemical energy of reactants is equal to energy of products plus energy given off –Some of the stored chemical energy of methane and oxygen is converted to heat as they react

Section 10.1 Energy, Temperature, and Heat Temperature is a measure of the random motions (kinetic energy) of the components of a substance. B. Temperature and Heat Hot waterCold water (90. o C) (10. o C) Fast Slow

Section 10.1 Energy, Temperature, and Heat Measuring Temperature

Section 10.1 Energy, Temperature, and Heat Heat transfer is a flow of energy between two objects due to a temperature difference between the objects. –Heat transfer is the way in which thermal energy is moved from a hot object to a colder object. B. Temperature and Heat Hot water Cold water (90. o C) (10. o C) Water Water (50. o C) (50. o C)

Section 10.1 Energy, Temperature, and Heat What is the difference between heat and temperature? Heat is the amount of thermal energy in an object because of its moving molecules. Temperature is a measure of thermal energy or how fast molecules are moving in an object. The more you heat something, the faster the molecules move. This is what causes temperature to rise.

Section 10.1 Energy, Temperature, and Heat What is the difference between heat and temperature? Heat and temperature are NOT the same thing. Temperature is a measure of the average kinetic energy of each particle within an object. Thermal (heat) energy is the total energy of the particles that make up an object For example, there is a lot more heat inside a glacier than in a pot of boiling water. The boiling water has a higher temperature, but the glacier has a lot more molecules. All the slower moving molecules in the large glacier equates to a higher thermal energy than the pot of hot water.

Section 10.1 Energy, Temperature, and Heat Which picture shows the object that has more kinetic energy of particles? Figure AFigure B

Section 10.1 Energy, Temperature, and Heat Heat Analogy Particles of hotter substances are like the people in a “mosh pit…”

Section 10.1 Energy, Temperature, and Heat …while particles of colder substances are more like the people at a tea party in a retirement home.

Section 10.1 Energy, Temperature, and Heat Heat Transfer The transition of thermal energy from a hotter to a cooler body Radiation Conduction Convection

Section 10.1 Energy, Temperature, and Heat CONDUCTION The transfer of heat energy between substances that are in direct contact with each other.

Section 10.1 Energy, Temperature, and Heat CONVECTION Occurs when areas of a liquid or gas at different temperatures rise and fall to due to density differences.

Section 10.1 Energy, Temperature, and Heat RADIATION Does not rely upon any contact between the heat source and heated material, as is the case with conduction and convection.

Section 10.1 Energy, Temperature, and Heat

Section 10.1 Energy, Temperature, and Heat Measuring Heat Calorie – Amount of heat required to raise the temperature of 1 gram of pure water by 1 ° C The SI unit for energy and heat is the Joule (J) (1J = calories or 1 calorie = J)

Section 10.1 Energy, Temperature, and Heat Specific Heat Specific heat of any substance is the amount of heat required to raise the temperature of 1 gram of that substance by 1 ° C. For example, the specific heat of water is J / g ° C which this is the amount of energy that must be absorbed by each gram of water to rise it by one degree. On the other hand, it only takes J of energy to raise the temperature of an equal mass of gold by one degree.

Section 10.1 Energy, Temperature, and Heat

Section 10.1 Energy, Temperature, and Heat 26 Examples of Specific Heats

Section 10.1 Energy, Temperature, and Heat Specific Heat The heat absorbed or released by a substance during a temperature change depends not only upon the specific heat of the substance, but also upon the mass of the substance and the amount by which the temperature changes. Q = c x m x ΔT Q = heat absorbed or released c = specific heat of substance (J / g ° C) m = mass of the sample in grams ΔT = change in temperature in ° C (T final - T initial )

Section 10.1 Energy, Temperature, and Heat C. Exothermic and Endothermic Processes System – part of the universe on which we focus attention Surroundings – everything else in the universe Look at the example of burning a match:

Section 10.1 Energy, Temperature, and Heat C. Exothermic and Endothermic Processes Exothermic – heat energy flows out of the system Endothermic – heat energy flows into the system