The Flow of Energy Heat and Work Chapter 17, Section 1 Heat and Work Chapter 17, Section 1

Energy Transformations Energy is the capacity for doing work or supplying heat. Energy is detected only by its effects: the motion of a thrown baseball the heat generated by a chemical reaction Energy is the capacity for doing work or supplying heat. Energy is detected only by its effects: the motion of a thrown baseball the heat generated by a chemical reaction

Energy Transformations Energy is the capacity for doing work or supplying heat. Energy is detected only by its effects: the motion of a thrown baseball the heat generated by a chemical reaction Thermochemistry is the study of energy changes in chemical reactions and changes of state. Energy is the capacity for doing work or supplying heat. Energy is detected only by its effects: the motion of a thrown baseball the heat generated by a chemical reaction Thermochemistry is the study of energy changes in chemical reactions and changes of state.

Energy Transformations Energy is the capacity for doing work or supplying heat. Energy is detected only by its effects: the motion of a thrown baseball the heat generated by a chemical reaction Thermochemistry is the study of energy changes in chemical reactions and changes of state. Chemical potential energy is the energy stored in chemical bonds. Energy is the capacity for doing work or supplying heat. Energy is detected only by its effects: the motion of a thrown baseball the heat generated by a chemical reaction Thermochemistry is the study of energy changes in chemical reactions and changes of state. Chemical potential energy is the energy stored in chemical bonds.

Energy Transformations Chemical potential energy is seen in the combustion of methane in a laboratory burner.

Energy Transformations Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2.

Energy Transformations Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame. Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame.

Energy Transformations Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame. C-H (in CH 4 ), and O-O (in O 2 ) bonds are broken. Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame. C-H (in CH 4 ), and O-O (in O 2 ) bonds are broken.

Energy Transformations Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame. C-H (in CH 4 ), and O-O (in O 2 ) bonds are broken. C-O (in CO 2 ) and O-H (in H 2 O) bonds are formed. Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame. C-H (in CH 4 ), and O-O (in O 2 ) bonds are broken. C-O (in CO 2 ) and O-H (in H 2 O) bonds are formed.

Energy Transformations Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame. C-H (in CH 4 ), and O-O (in O 2 ) bonds are broken. C-O (in CO 2 ) and O-H (in H 2 O) bonds are formed. Energy is released. Chemical potential energy is seen in the combustion of methane in a laboratory burner. Methane, CH 4, is added to the burner with oxygen gas, O 2. A spark is added to the mixture and there is a flame. C-H (in CH 4 ), and O-O (in O 2 ) bonds are broken. C-O (in CO 2 ) and O-H (in H 2 O) bonds are formed. Energy is released.

Energy Transformations methane

methane oxygen gas

Energy Transformations methane oxygen gas breaking bonds...

Energy Transformations

making bonds...

Energy Transformations

carbondioxide water

carbondioxide water plus energy

Energy Transformations carbondioxide water plus energy CH 4 (g) + 2 O 2 (g) → CO 2 (g) + 2 H 2 O(l)

Energy Transformations Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects. Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects.

Energy Transformations Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects. Heat always flows from a warm object to a cooler object. Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects. Heat always flows from a warm object to a cooler object.

Energy Transformations Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects. Heat always flows from a warm object to a cooler object. If the two objects are in contact, and remain in contact, they will become the same temperature. Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects. Heat always flows from a warm object to a cooler object. If the two objects are in contact, and remain in contact, they will become the same temperature.

Exo- and Endothermic Processes A chemical reaction is part of a system.

Exo- and Endothermic Processes A chemical reaction is part of a system. Everything outside the system is called the surroundings.

Exo- and Endothermic Processes A chemical reaction is part of a system. Everything outside the system is called the surroundings. system surroundings

Exo- and Endothermic Processes Energy is not created or destroyed system surroundings

Exo- and Endothermic Processes Energy is not created or destroyed The total amount of energy in the system and the surroundings must remain the same. Energy is not created or destroyed The total amount of energy in the system and the surroundings must remain the same. system surroundings

Exo- and Endothermic Processes If the chemical reaction in the system uses energy system surroundings

Exo- and Endothermic Processes If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. system surroundings

Exo- and Endothermic Processes If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. system surroundings This is an endothermic process.

surroundings Exo- and Endothermic Processes If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. system This is an endothermic process. energy

surroundings Exo- and Endothermic Processes If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. If the chemical reaction in the system uses energy then energy is transferred from the surroundings into the system. system This is an endothermic process. In an endothermic process, the system gains heat while the surroundings cool down. energy

Exo- and Endothermic Processes If the chemical reaction in the system makes energy system surroundings

Exo- and Endothermic Processes If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. system surroundings

Exo- and Endothermic Processes If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. This is an exothermic process. system surroundings

surroundings Exo- and Endothermic Processes If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. This is an exothermic process. system energy

surroundings Exo- and Endothermic Processes If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. If the chemical reaction in the system makes energy then energy is transferred from the system out to the surroundings. This is an exothermic process. system In an exothermic process, the system cools down while the surroundings gain heat. energy

Units for Measuring Heat Flow We measure heat flow in two common units:

Units for Measuring Heat Flow We measure heat flow in two common units: the calorie (cal) the joule (J) We measure heat flow in two common units: the calorie (cal) the joule (J)

Units for Measuring Heat Flow We measure heat flow in two common units: the calorie (cal) the joule (J) The calorie (with a lower case “c”) is... We measure heat flow in two common units: the calorie (cal) the joule (J) The calorie (with a lower case “c”) is...

Units for Measuring Heat Flow We measure heat flow in two common units: the calorie (cal) the joule (J) The calorie (with a lower case “c”) is... a non-SI unit. the amount of heat to increase the temperature of exactly 1 g of water by exactly 1°C. equal to Calories (food calories or Cal). There are 1,000 cal in 1 Cal. We measure heat flow in two common units: the calorie (cal) the joule (J) The calorie (with a lower case “c”) is... a non-SI unit. the amount of heat to increase the temperature of exactly 1 g of water by exactly 1°C. equal to Calories (food calories or Cal). There are 1,000 cal in 1 Cal.

Units for Measuring Heat Flow We measure heat flow in two common units: the calorie (cal) the joule (J) The joule is... We measure heat flow in two common units: the calorie (cal) the joule (J) The joule is...

Units for Measuring Heat Flow We measure heat flow in two common units: the calorie (cal) the joule (J) The joule is... the SI unit for heat (and energy and work). the energy required to apply 1 newton of force (about 3.6 ounces) over a distance of 1 meter. equal to cal. There are cal in 1 J. We measure heat flow in two common units: the calorie (cal) the joule (J) The joule is... the SI unit for heat (and energy and work). the energy required to apply 1 newton of force (about 3.6 ounces) over a distance of 1 meter. equal to cal. There are cal in 1 J.

Units for Measuring Heat Flow We measure heat flow in two common units: the calorie (cal) the joule (J) We will be using the joule exclusively in this course. We measure heat flow in two common units: the calorie (cal) the joule (J) We will be using the joule exclusively in this course.

Units for Measuring Heat Flow We measure heat flow in two common units: the calorie (cal) the joule (J) We will be using the joule exclusively in this course. You will not be required to convert from J ➔ cal or from cal ➔ J. We measure heat flow in two common units: the calorie (cal) the joule (J) We will be using the joule exclusively in this course. You will not be required to convert from J ➔ cal or from cal ➔ J.

Heat Capacity and Specific Heat The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object.

Heat Capacity and Specific Heat The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its... mass chemical composition The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its... mass chemical composition

Heat Capacity and Specific Heat The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its... mass chemical composition It takes more heat to increase the T of 1 kg of water than it does to increase the T of 1 g of water. The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its... mass chemical composition It takes more heat to increase the T of 1 kg of water than it does to increase the T of 1 g of water.

Heat Capacity and Specific Heat The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its... mass chemical composition It takes more heat to increase the T of 1 kg of water than it does to increase the T of 1 g of water. It takes more heat to increase the T of 1 kg of water than it does to increase the T of 1 kg of iron. The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its... mass chemical composition It takes more heat to increase the T of 1 kg of water than it does to increase the T of 1 g of water. It takes more heat to increase the T of 1 kg of water than it does to increase the T of 1 kg of iron.

Heat Capacity and Specific Heat The amount of heat needed to increase the temperature of an object with a mass of exactly 1 g by exactly 1°C is called the specific heat capacity or the specific heat, C, of that object.

Heat Capacity and Specific Heat The amount of heat needed to increase the temperature of an object with a mass of exactly 1 g by exactly 1°C is called the specific heat capacity or the specific heat, C, of that object. Different objects have different specific heats. The amount of heat needed to increase the temperature of an object with a mass of exactly 1 g by exactly 1°C is called the specific heat capacity or the specific heat, C, of that object. Different objects have different specific heats. substanceC (J/g°C)C (cal/g°C) water ice2.1o.50 steam aluminum, Al iron, Fe silver, Ag

Heat Capacity and Specific Heat Water has a very high specific heat.

Heat Capacity and Specific Heat Water has a very high specific heat. C = 4.18 J/ g°C. Water has a very high specific heat. C = 4.18 J/ g°C.

Heat Capacity and Specific Heat Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature. Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature.

Heat Capacity and Specific Heat Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature. It also means that we get a lot of heat out of water when we decrease its temperature. Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature. It also means that we get a lot of heat out of water when we decrease its temperature.

Heat Capacity and Specific Heat Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature. It also means that we get a lot of heat out of water when we decrease its temperature. Farmers use this to protect crops in danger of freezing. Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature. It also means that we get a lot of heat out of water when we decrease its temperature. Farmers use this to protect crops in danger of freezing.

Heat Capacity and Specific Heat Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature. It also means that we get a lot of heat out of water when we decrease its temperature. This is why the filling in a hot apple pie is more likely to burn your tongue than is the crust. Water has a very high specific heat. C = 4.18 J/ g°C. This means that you must add a lot of heat to water to increase its temperature. It also means that we get a lot of heat out of water when we decrease its temperature. This is why the filling in a hot apple pie is more likely to burn your tongue than is the crust.

Heat Capacity and Specific Heat To calculate the specific heat, C, of a material you divide the amount of heat input, q, by the mass, m, times the temperature change, ∆T. To calculate the specific heat, C, of a material you divide the amount of heat input, q, by the mass, m, times the temperature change, ∆T. Cqm×∆T =

Heat Capacity and Specific Heat To calculate the specific heat, C, of a material you divide the amount of heat input, q, by the mass, m, times the temperature change, ∆T. To calculate the specific heat, C, of a material you divide the amount of heat input, q, by the mass, m, times the temperature change, ∆T. Cqm×∆T = We can use this to calculate the specific heat of any material.

Heat Capacity and Specific Heat Sample Problem 17.1 (page 510):

Heat Capacity and Specific Heat Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper?

Heat Capacity and Specific Heat Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g

Heat Capacity and Specific Heat Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g Cqm×∆T =

Heat Capacity and Specific Heat Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g Cqm×∆T = = 849 J (95.4 g)(23.0°C)

Heat Capacity and Specific Heat Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g Sample Problem 17.1 (page 510): The temperature of a 95.4 g piece of copper increases from 25.0°C to 48.0°C when the copper absorbs 849 J of heat. What is the specific heat of copper? q = 849 J ∆T = T f − T i = 48.0°C − 25.0°C = 23.0°C m = 95.4 g Cqm×∆T = = 849 J (95.4 g)(23.0°C) = J/g°C

Summary

Energy is the capacity for doing work or supplying heat. Thermochemistry is the study of energy changes in chemical reactions and changes of state. Chemical potential energy is the energy stored in chemical bonds. Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects. Energy is the capacity for doing work or supplying heat. Thermochemistry is the study of energy changes in chemical reactions and changes of state. Chemical potential energy is the energy stored in chemical bonds. Heat, symbolized by q, is the transfer of energy from one object to another due to the temperature difference between the two objects.

Summary A chemical reaction is part of a system. Everything outside the system is called the surroundings. Energy is not created or destroyed, which means that the total amount of energy in the system and the surroundings must remain the same. A chemical reaction is part of a system. Everything outside the system is called the surroundings. Energy is not created or destroyed, which means that the total amount of energy in the system and the surroundings must remain the same.

Summary If the chemical reaction in the system uses energy, then energy is transferred from the surroundings into the system (an endothermic reaction). If the chemical reaction in the system makes energy, then energy is transferred from the system into the surroundings (an exothermic reaction). If the chemical reaction in the system uses energy, then energy is transferred from the surroundings into the system (an endothermic reaction). If the chemical reaction in the system makes energy, then energy is transferred from the system into the surroundings (an exothermic reaction).

Summary We measure heat flow in two common units: the calorie (cal), which we will not use and the joule (J), which we will use. The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its mass and its chemical composition. We measure heat flow in two common units: the calorie (cal), which we will not use and the joule (J), which we will use. The amount of heat needed to increase the temperature of an object by exactly 1°C is called the heat capacity of that object. The heat capacity of an object depends on both its mass and its chemical composition.

Summary The amount of heat needed to increase the temperature of an object with a mass of exactly 1 g by exactly 1°C is called the specific heat capacity or the specific heat, C, of that object. To calculate the specific heat, C, of a material you divide the amount of heat input, q, by the mass, m, times the temperature change, ∆T. The amount of heat needed to increase the temperature of an object with a mass of exactly 1 g by exactly 1°C is called the specific heat capacity or the specific heat, C, of that object. To calculate the specific heat, C, of a material you divide the amount of heat input, q, by the mass, m, times the temperature change, ∆T. Cqm×∆T =