2 Chap 2.1 Energy (learning target) Explain that physical and chemical changes in matter involve transfers of energy.Apply the law of conservation of energy to analyze changes in matter.Distinguish between heat and temperature.Convert between the Celsius and Kelvin temperature scales.
3 Chap 2.1 EnergyWork in small groups to brainstorm ideas relating to energy.List different types of energy, list why energy is important, and when energy is released or absorbed.After brainstorming for five minutes, examine your lists and write your own definition for energy.
4 Energy and Energy Changes What is the energy?Energy is the capacity to do some kind of work, such as moving an object, forming a new compound, transferring heat or generating light.
5 Energy is always involved when there is a change in matter. All physical and chemical changes involve energyEnergy may affect matter:(raise its temperature, eventually change a state)
6 Two processes Exothermic Any change in matter in which energy is absorbed from the surroundings is an endothermic process.EndothermicAny change in matter in which energy is released is an exothermic process.Energy is releasedEnergy is absorbed
7 Conservation law of Energy Energy can be absorbed by the surroundings or released to the surroundings, but it cannot be created or destroyed.The law of conservation of energy states that during any physical or chemical change, the total quantity of energy remains constant.Energy can be transfer one form to another form.
8 To keep track of energy changes, chemists use the terms system and surroundings. A system consists of all the components that are being studied at any given time. The surroundings include everything outside the system.systemsurrounding
9 Energy exists in different forms, including : chemicalmechanicallightheatelectricalsound
10 HeatHeat is the energy transferred between objects that are at different temperatures.Heat energy is always transferred from a warmer object to a cooler object.
11 Temperature Temperature indicates how hot or cold something is. Temperature as a measurement of the average kinetic energy of the random motion of particles in a substance.The transfer of energy as heat can be measured by calculating changes in temperature.
12 Temperature Temperature can be measured in a variety of units. Celsius , Kelvin, FahrenheitThe zero point on the Celsius scale is designated as the freezing point of water.The zero point on the Kelvin scale is designated as absolute zero, the temperature at which the minimum average kinetic energies of all particles occur.
14 Conversions for C and KUse the following equations in such conversions:T (Kelvin) = t (Celsius)t = T –AssignmentsPage 45 #1-13Worksheet “Temperature”
15 The transfer of energy as heat does not always result in a change of temperature. The temperature of the mixture remains at 0°C until all of the ice has melted.Once all the ice has melted, the temperature of the water will start to increase until it reaches 100°C.As the water boils, the temperature remains at 100°C until all the water has turned into a gas.
16 Transfer of Heat Affects Substances Differently If you transfer the same quantity of heat to similar masses of different substances, they do not show the same increase in temperature.This relationship between energy transferred as heat to a substance and the substance’s temperature change is called the specific heat.The specific heat of a substance is the quantity of energy as heat that must be transferred to raise the temperature of 1 g of a substance 1 K.
18 Energy Unit Calorie (cal) Energy (heat) required to raise temperature of one gram of water by one Celsius degree.Joule (J)The SI unit for energy is the joule (J).1 cal = JSpecific heat is expressed in joules per gram kelvin (J/g•K).
29 Understanding Concepts Chapter 2Standardized Test PreparationUnderstanding Concepts5. Use the concept of specific heat to analyze the following observation: two pieces of metal with exactly the same mass are placed on a surface in bright sunlight. The temperature of the first block increases by 3°C while the temperature of the second increases by 8°C.Answer: Because the temperatures of the objects differ under the same conditions, they must have different specific heats, so they are made of different metals.