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Exothermic and Endothermic Reations

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Sangeetha Balakrishnan

This document provides instruction on exothermic and endothermic reactions through a series of exercises. It aims to help students understand key concepts like: a) Defining exothermic and endothermic reactions with examples b) Relating these reactions to everyday processes using a system-surroundings model c) Representing them in terms of potential energy diagrams Students are given sample experiments involving ammonium nitrate and calcium chloride and asked questions to assess whether the reactions are exothermic or endothermic based on temperature changes. Other questions classify common reactions and analyze potential energy graphs. The learning objectives are to define key terms and grasp the system-surroundings framework for these reaction types.

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ExothermicandEndothermicReactions Exothermic and Endothermic Reactions Objective: To assess students¡¯ understanding of the concepts of exothermic and endothermic reactions. Learning Outcomes: At the end of this assignment students will be able to: a) Define exothermic and endothermic reactions and give examples. b) Understand exothermic and endothermic reactions relating it to everyday processes. c) Represent exothermic and endothermic reactions from a potential energy standpoint. d) Get a firm grasp on the concept of system and surroundings which underpins this assignment.
ExothermicandEndothermicReactions Exercise 1 Q1a. Consider this: An open vessel containing water is kept on the stove for heating. As the temperature rises, certain changes occur between the system (the open vessel) and the atmosphere (the surroundings). These changes are depicted by the arrows in the picture that follows. Study the picture and explain briefly the processes happening therein. Q1b. Define an open system. Q1c. Consider this: A vessel containing water is kept on the stove for heating. It is now covered using a lid. As the temperature rises, certain changes occur between the system (the covered vessel) and the atmosphere (the surroundings). These changes are depicted by the arrows in the picture that follows. Study the picture and explain briefly the processes happening therein. Q1d. Define a closed system.
ExothermicandEndothermicReactions Q1e. Consider this: Hot coffee is kept in a thermos flask at time, t =0. Let¡¯s say, at time t = 30 minutes, the amount and the temperature of the coffee in the thermos remains the same. Study the picture and explain briefly the significance of the system. Q1f. Define an isolated system. +++
ExothermicandEndothermicReactions Exercise 2 Consider the following experiment. Procedure: 1. About 100 mL water is taken in a beaker. 2. To the water, about 5g of ammonium nitrate is added and stirred well. 3. The solution is allowed to stand for a few seconds and its temperature is recorded. 4. This is called the starting temperature, and is found to be, let¡¯s say, 25 ¡ãC. 5. The beaker is left unattended for about five minutes and the temperature is again noted. 6. This is called the closing temperature, and is found to be, let¡¯s say, 5 ¡ãC. Starting temperature: _______________ ?C Ending temperature: _______________ ?C Questions: Q 2a. What type of reaction, do you think, occurred in the test tube - exothermic or endothermic? How do you know? Q 2b. What do you think could be a possible application of this set up? +++
ExothermicandEndothermicReactions Exercise 3 Consider the following experiment. Procedure: 1. About 100 mL water is taken in a beaker. 2. To the water, about 5g of calcium chloride is added and stirred well. 3. The solution is allowed to stand for a few seconds and its temperature is recorded. 4. This is called the starting temperature, and is found to be, let¡¯s say, 25 ¡ãC. 5. The beaker is left unattended for about five minutes and the temperature is again noted. 6. This is called the closing temperature, and is found to be, let¡¯s say, 40 ¡ãC. Starting temperature: _______________ ?C Ending temperature: _______________ ?C Questions: Q 3a. What type of reaction, do you think, occurred in the test tube - exothermic or endothermic? How do you know? Q 3b. What do you think could be a possible application of this set up? +++
ExothermicandEndothermicReactions Exercise 4 Classify the following reactions as exothermic or endothermic. ? Melting of ice ? Freezing of ice ? Burning of a candle ? An explosion ? Photosynthesis ? Cooking rice Q 4a. Define an exothermic reaction. Q 4b. State T/F: In an exothermic reaction, the temperature of the immediate surroundings rises. Q 4c. Define an endothermic reaction. Q 4d. State T/F: In an endothermic reaction, the temperature of the immediate surroundings decreases. +++
ExothermicandEndothermicReactions Exercise 5 Study the following graph and answer the question that follows. Q5a. Which of the two graphs corresponds to exothermic reaction? Justify your answer. Q5b. Which of the two graphs corresponds to endothermic reaction? Justify your answer. +++ Web references: http://antoine.frostburg.edu/chem/senese/101/thermo/faq/exothermic-endothermic- examples.shtml http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Thermodynamics/A_System_And_Its_Su rroundings https://socratic.org/questions/how-can-i-represent-the-activation-energy-in-a-potential-energy- diagram

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Exothermic and Endothermic Reations

  • 1. ExothermicandEndothermicReactions Exothermic and Endothermic Reactions Objective: To assess students¡¯ understanding of the concepts of exothermic and endothermic reactions. Learning Outcomes: At the end of this assignment students will be able to: a) Define exothermic and endothermic reactions and give examples. b) Understand exothermic and endothermic reactions relating it to everyday processes. c) Represent exothermic and endothermic reactions from a potential energy standpoint. d) Get a firm grasp on the concept of system and surroundings which underpins this assignment.
  • 2. ExothermicandEndothermicReactions Exercise 1 Q1a. Consider this: An open vessel containing water is kept on the stove for heating. As the temperature rises, certain changes occur between the system (the open vessel) and the atmosphere (the surroundings). These changes are depicted by the arrows in the picture that follows. Study the picture and explain briefly the processes happening therein. Q1b. Define an open system. Q1c. Consider this: A vessel containing water is kept on the stove for heating. It is now covered using a lid. As the temperature rises, certain changes occur between the system (the covered vessel) and the atmosphere (the surroundings). These changes are depicted by the arrows in the picture that follows. Study the picture and explain briefly the processes happening therein. Q1d. Define a closed system.
  • 3. ExothermicandEndothermicReactions Q1e. Consider this: Hot coffee is kept in a thermos flask at time, t =0. Let¡¯s say, at time t = 30 minutes, the amount and the temperature of the coffee in the thermos remains the same. Study the picture and explain briefly the significance of the system. Q1f. Define an isolated system. +++
  • 4. ExothermicandEndothermicReactions Exercise 2 Consider the following experiment. Procedure: 1. About 100 mL water is taken in a beaker. 2. To the water, about 5g of ammonium nitrate is added and stirred well. 3. The solution is allowed to stand for a few seconds and its temperature is recorded. 4. This is called the starting temperature, and is found to be, let¡¯s say, 25 ¡ãC. 5. The beaker is left unattended for about five minutes and the temperature is again noted. 6. This is called the closing temperature, and is found to be, let¡¯s say, 5 ¡ãC. Starting temperature: _______________ ?C Ending temperature: _______________ ?C Questions: Q 2a. What type of reaction, do you think, occurred in the test tube - exothermic or endothermic? How do you know? Q 2b. What do you think could be a possible application of this set up? +++
  • 5. ExothermicandEndothermicReactions Exercise 3 Consider the following experiment. Procedure: 1. About 100 mL water is taken in a beaker. 2. To the water, about 5g of calcium chloride is added and stirred well. 3. The solution is allowed to stand for a few seconds and its temperature is recorded. 4. This is called the starting temperature, and is found to be, let¡¯s say, 25 ¡ãC. 5. The beaker is left unattended for about five minutes and the temperature is again noted. 6. This is called the closing temperature, and is found to be, let¡¯s say, 40 ¡ãC. Starting temperature: _______________ ?C Ending temperature: _______________ ?C Questions: Q 3a. What type of reaction, do you think, occurred in the test tube - exothermic or endothermic? How do you know? Q 3b. What do you think could be a possible application of this set up? +++
  • 6. ExothermicandEndothermicReactions Exercise 4 Classify the following reactions as exothermic or endothermic. ? Melting of ice ? Freezing of ice ? Burning of a candle ? An explosion ? Photosynthesis ? Cooking rice Q 4a. Define an exothermic reaction. Q 4b. State T/F: In an exothermic reaction, the temperature of the immediate surroundings rises. Q 4c. Define an endothermic reaction. Q 4d. State T/F: In an endothermic reaction, the temperature of the immediate surroundings decreases. +++
  • 7. ExothermicandEndothermicReactions Exercise 5 Study the following graph and answer the question that follows. Q5a. Which of the two graphs corresponds to exothermic reaction? Justify your answer. Q5b. Which of the two graphs corresponds to endothermic reaction? Justify your answer. +++ Web references: http://antoine.frostburg.edu/chem/senese/101/thermo/faq/exothermic-endothermic- examples.shtml http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Thermodynamics/A_System_And_Its_Su rroundings https://socratic.org/questions/how-can-i-represent-the-activation-energy-in-a-potential-energy- diagram