Chapter 2 sec 1 Intro Energy

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.

Chap 2.1 Energy Work 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.

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.

Energy is always involved when there is a change in matter. All physical and chemical changes involve energy Energy may affect matter: (raise its temperature, eventually change a state)

Two processes Exothermic Any change in matter in which energy is absorbed from the surroundings is an endothermic process. Endothermic Any change in matter in which energy is released is an exothermic process. Energy is released Energy is absorbed

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.

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. system surrounding

Energy exists in different forms, including : chemical mechanical light heat electrical sound

Heat Heat is the energy transferred between objects that are at different temperatures. Heat energy is always transferred from a warmer object to a cooler object.

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.

Temperature Temperature can be measured in a variety of units. Celsius , Kelvin, Fahrenheit The 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.

Temperature

Conversions for C and K Use the following equations in such conversions: T (Kelvin) = t (Celsius) + 273.15 t = T – 273.15 Assignments Page 45 #1-13 Worksheet “Temperature”

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.

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.

Heating Curve for Water

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 = 4.184 J Specific heat is expressed in joules per gram kelvin (J/g•K).

Calculating Specific Heat Chapter 2 Calculating Specific Heat Sample Problem B A 4.0 g sample of glass was heated from 274 K to 314 K and was found to absorb 32 J of energy as heat. Calculate the specific heat of this glass. Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 1. Which of the following determines the temperature of a substance? A. charge on ions B. color C. motion of particles D. total mass of material Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 1. Which of the following determines the temperature of a substance? A. charge on ions B. color C. motion of particles D. total mass of material Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 2. Which of these processes is an endothermic physical change? F. an explosion G. melting of butter H. condensation of a gas I. formation of a solid when two liquids are mixed Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 2. Which of these processes is an endothermic physical change? F. an explosion G. melting of butter H. condensation of a gas I. formation of a solid when two liquids are mixed Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 3. Which of the following definitely indicates an error in an experiment? A. hypothesis not supported B. results contradict a theory C. unexpected results D. violation of a scientific law Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 3. Which of the following definitely indicates an error in an experiment? A. hypothesis not supported B. results contradict a theory C. unexpected results D. violation of a scientific law Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 4. Every chemical change involves F. the formation of a different substance. G. the vaporization of a liquid. H. separation of states of matter. I. the release of energy. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 4. Every chemical change involves F. the formation of a different substance. G. the vaporization of a liquid. H. separation of states of matter. I. the release of energy. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 5. 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. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Understanding Concepts Chapter 2 Standardized Test Preparation Understanding Concepts 5. 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.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics Use the graph below to answer questions 9–12. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 9. What is happening during the portion of the graph labeled Heat of Vaporization, in which temperature does not change? A. No energy is added to the water. B. Added energy causes water molecules to move closer together. C. Added energy causes the water molecules to move farther apart. D. Added energy causes the water molecules to change from the solid state to the gas state. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 9. What is happening during the portion of the graph labeled Heat of Vaporization, in which temperature does not change? A. No energy is added to the water. B. Added energy causes water molecules to move closer together. C. Added energy causes the water molecules to move farther apart. D. Added energy causes the water molecules to change from the solid state to the gas state. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 10. For a given mass of water, which of these processes requires the greatest addition of energy for a 1°C temperature change F. heating a gas G. heating a solid H. heating a liquid I. changing a solid to a liquid Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 10. For a given mass of water, which of these processes requires the greatest addition of energy for a 1°C temperature change F. heating a gas G. heating a solid H. heating a liquid I. changing a solid to a liquid Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 11. How does the temperature change between the beginning of vaporization and the end of vaporization of water? A. temperature decreases slowly B. temperature does not change C. temperature increases slowly D. temperature increases rapidly Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 11. How does the temperature change between the beginning of vaporization and the end of vaporization of water? A. temperature decreases slowly B. temperature does not change C. temperature increases slowly D. temperature increases rapidly Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 12. On what portion of this graph are water molecules separated by the greatest distance? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interpreting Graphics Chapter 2 Standardized Test Preparation Interpreting Graphics 12. On what portion of this graph are water molecules separated by the greatest distance? Answer: The right side of the graph, which shows the conditions of water in the gas phase. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.