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Enthalpy Changes in Chemical Reactions; This lesson explores how chemical reactions involve energy changes that can be exo or endothermic.
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Lesson Plan: Enthalpy Changes in Chemical Reactions
Grade/Level: Secondary / IGCSE / AS level
Duration: 60 minutes
Topic: Enthalpy Changes in Reactions
Lesson Objectives
By the end of the lesson, students should be able to:
1. Understand that chemical reactions are accompanied by enthalpy changes, which can be exothermic or endothermic.
2. Construct and interpret reaction pathway diagrams, showing enthalpy change and activation energy.
3. Define and use key terms: standard conditions (⦵), enthalpy change of reaction (ΔHr⦵), formation (ΔHf⦵), combustion (ΔHc⦵), and neutralisation (ΔHneut⦵).
Lesson Breakdown (60 minutes)
1. Introduction (5 minutes)
Begin with a real-life hook:
Ask: “Why does burning wood release heat, but dissolving ammonium nitrate in water feels cold?”
Link to lesson: These are examples of exothermic and endothermic reactions.
2. Theory: Enthalpy Changes (10 minutes)
Define enthalpy (H): The heat content of a system at constant pressure.
Define enthalpy change (ΔH): Heat energy transferred during a reaction at constant pressure.
Distinguish:
Exothermic reaction: ΔH is negative (heat released).
Endothermic reaction: ΔH is positive (heat absorbed).
Give simple examples:
Exothermic → combustion of methane.
Endothermic → thermal decomposition of calcium carbonate.
3. Reaction Pathway Diagrams (15 minutes)
Draw and explain two diagrams:
Exothermic pathway: Products lower in energy than reactants, ΔH negative.
Endothermic pathway: Products higher in energy than reactants, ΔH positive.
Introduce activation energy (Ea):Minimum energy needed for reaction to occur.
Label diagrams clearly:
Reactants → peak (activation energy) → products.
Highlight ΔH and Ea.
4. Standard Conditions and Key Enthalpy Terms (15 minutes)
Explain standard conditions (⦵):
298 K (25°C), 101 kPa pressure, substances in standard states.
Define and discuss:
Standard enthalpy change of reaction (ΔHr⦵): Heat change when reaction occurs in molar quantities under standard conditions.
Standard enthalpy of formation (ΔHf⦵): Heat change when 1 mole of compound is formed from its elements in their standard states.
Standard enthalpy of combustion (ΔHc⦵):Heat change when 1 mole of substance is completely burnt in oxygen under standard conditions.
Standard enthalpy of neutralisation (ΔHneut⦵): Heat change when an acid and alkali react to form 1 mole of water under standard conditions.
Use simple examples for each (e.g., combustion of methane, formation of H2O, neutralisation of HCl with NaOH).
5. Guided Practice / Mini Activity (10 minutes)
Students sketch their own reaction pathway diagrams (exothermic and endothermic).
Label ΔH and Ea.
Pair discussion: “Why do we still need activation energy even for exothermic reactions?”
6. Exercise (Homework / Classwork) (5 minutes)
Answer the following questions:
1. State whether each reaction is exothermic or endothermic:
a) Burning propane gas in oxygen.
b) Photosynthesis in plants.
c) Dissolving anhydrous copper(II) sulfate in water.
2. On a reaction pathway diagram:
Show ΔH and Ea for an endothermic reaction.
3. Define the following terms and give one example each:
a) Standard enthalpy of formation (ΔHf⦵)
b) Standard enthalpy of combustion (ΔHc⦵)
c) Standard enthalpy of neutralisation (ΔHneut⦵)
4. Under standard conditions, the enthalpy of combustion of methane is –890 kJ mol−1.
Grade/Level: Secondary / IGCSE / AS level
Duration: 60 minutes
Topic: Enthalpy Changes in Reactions
Lesson Objectives
By the end of the lesson, students should be able to:
1. Understand that chemical reactions are accompanied by enthalpy changes, which can be exothermic or endothermic.
2. Construct and interpret reaction pathway diagrams, showing enthalpy change and activation energy.
3. Define and use key terms: standard conditions (⦵), enthalpy change of reaction (ΔHr⦵), formation (ΔHf⦵), combustion (ΔHc⦵), and neutralisation (ΔHneut⦵).
Lesson Breakdown (60 minutes)
1. Introduction (5 minutes)
Begin with a real-life hook:
Ask: “Why does burning wood release heat, but dissolving ammonium nitrate in water feels cold?”
Link to lesson: These are examples of exothermic and endothermic reactions.
2. Theory: Enthalpy Changes (10 minutes)
Define enthalpy (H): The heat content of a system at constant pressure.
Define enthalpy change (ΔH): Heat energy transferred during a reaction at constant pressure.
Distinguish:
Exothermic reaction: ΔH is negative (heat released).
Endothermic reaction: ΔH is positive (heat absorbed).
Give simple examples:
Exothermic → combustion of methane.
Endothermic → thermal decomposition of calcium carbonate.
3. Reaction Pathway Diagrams (15 minutes)
Draw and explain two diagrams:
Exothermic pathway: Products lower in energy than reactants, ΔH negative.
Endothermic pathway: Products higher in energy than reactants, ΔH positive.
Introduce activation energy (Ea):Minimum energy needed for reaction to occur.
Label diagrams clearly:
Reactants → peak (activation energy) → products.
Highlight ΔH and Ea.
4. Standard Conditions and Key Enthalpy Terms (15 minutes)
Explain standard conditions (⦵):
298 K (25°C), 101 kPa pressure, substances in standard states.
Define and discuss:
Standard enthalpy change of reaction (ΔHr⦵): Heat change when reaction occurs in molar quantities under standard conditions.
Standard enthalpy of formation (ΔHf⦵): Heat change when 1 mole of compound is formed from its elements in their standard states.
Standard enthalpy of combustion (ΔHc⦵):Heat change when 1 mole of substance is completely burnt in oxygen under standard conditions.
Standard enthalpy of neutralisation (ΔHneut⦵): Heat change when an acid and alkali react to form 1 mole of water under standard conditions.
Use simple examples for each (e.g., combustion of methane, formation of H2O, neutralisation of HCl with NaOH).
5. Guided Practice / Mini Activity (10 minutes)
Students sketch their own reaction pathway diagrams (exothermic and endothermic).
Label ΔH and Ea.
Pair discussion: “Why do we still need activation energy even for exothermic reactions?”
6. Exercise (Homework / Classwork) (5 minutes)
Answer the following questions:
1. State whether each reaction is exothermic or endothermic:
a) Burning propane gas in oxygen.
b) Photosynthesis in plants.
c) Dissolving anhydrous copper(II) sulfate in water.
2. On a reaction pathway diagram:
Show ΔH and Ea for an endothermic reaction.
3. Define the following terms and give one example each:
a) Standard enthalpy of formation (ΔHf⦵)
b) Standard enthalpy of combustion (ΔHc⦵)
c) Standard enthalpy of neutralisation (ΔHneut⦵)
4. Under standard conditions, the enthalpy of combustion of methane is –890 kJ mol−1.
Extra information
Students are advised to carry all necessary science instrument.
Location
At student's location :
- Around Amsterdam, Netherlands
Online from Zambia
About Me
Experienced Science Educator with nearly a decade of teaching Biology and Chemistry across A Level, AS Level, O Level, IGCSE, Edexcel, and IB curricula, complemented by proficiency in Physics and Mathematics. Passionate about problem-solving, scientific inquiry, and continuous learning through documentaries and research, I am dedicated to delivering high-quality education that inspires curiosity, fosters critical thinking, and drives academic excellence in students.
Education
Bachelor’s Degree in Science Education – Kwame Nkrumah University, 2022 Certificate of Completion in Science Teaching Capital- Cambridge university press Science Practical in Blended Education – Cambridge university press
Experience / Qualifications
I am an experienced educator with four years of teaching Chemistry, Biology, Physics, and Mathematics across multiple curricula, including A Level, IGCSE, Edexcel, and IB. I also lead a team of trained teachers specializing in Commercial subjects, Computer Science, and ICT, fostering a collaborative and multidisciplinary approach to learning. Committed to high-quality education, I focus on developing critical thinking, problem-solving skills, and academic excellence in all students.
Age
Teenagers (13-17 years old)
Adults (18-64 years old)
Seniors (65+ years old)
Student level
Beginner
Intermediate
Advanced
Duration
60 minutes
The class is taught in
English
Skills
Availability of a typical week
(GMT -05:00)
New York
Online via webcam
At student's home
Mon
Tue
Wed
Thu
Fri
Sat
Sun
00-04
04-08
08-12
12-16
16-20
20-24
Lesson: Electrochemistry
Duration: 60 minutes
Grade Level: Advanced Science / Chemistry (IGCSE, A Level, IB)
Main Objectives:
By the end of this lesson, students should be able to:
1. Define electrochemistry and explain its importance.
2. Describe the difference between electrolytic and galvanic (voltaic) cells.
3. Write half-reactions and overall cell reactions.
4. Calculate standard electrode potentials and predict the direction of electron flow.
5. Understand practical applications of electrochemistry in everyday life.
Lesson Outline / Brief Notes:
1. Introduction to Electrochemistry (10 minutes)
Definition: Electrochemistry is the branch of chemistry that deals with the relationship between chemical reactions and electricity.
Key Concept: Redox reactions involve the transfer of electrons.
Real-life example: Batteries, electroplating, corrosion prevention.
2. Galvanic (Voltaic) Cells (15 minutes)
Composed of two half-cells connected by a salt bridge.
Oxidation occurs at the anode, reduction at the cathode.
Example: Daniell cell
Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s)
Oxidation: Zn → Zn2+ + 2e−
Reduction: Cu2+ + 2e− → Cu
3. Electrolytic Cells (10 minutes)
Require an external power source to drive non-spontaneous reactions.
Example: Electrolysis of molten NaCl
At cathode: Na+ + e− → Na
At anode: 2Cl− → Cl2 + 2e-
4. Standard Electrode Potentials (10 minutes)
Electrode potential measures the tendency of a species to be reduced.
Example:
Zn2+/Zn: -0.76 V
Cu2+/Cu: +0.34 V
Predict electron flow: Electrons flow from Zn to Cu in a Daniell cell.
5. Applications of Electrochemistry (5 minutes)
Batteries (Li-ion, lead-acid)
Electroplating (silver plating, chromium plating)
Corrosion protection (galvanization)
Exercise (10 minutes)
1. Short Answer Questions:
a. Define electrochemistry.
b. Identify the anode and cathode in a zinc-copper galvanic cell.
c. Explain the difference between galvanic and electrolytic cells.
2. Calculation:
Given:
Zn2+/Zn: -0.76 V
Cu2+/Cu: +0.34 V
Calculate the standard cell potential of a Daniell cell.
3. Application Question:
Describe one practical application of electrochemistry in everyday life and explain how it works.
Duration: 60 minutes
Grade Level: Advanced Science / Chemistry (IGCSE, A Level, IB)
Main Objectives:
By the end of this lesson, students should be able to:
1. Define electrochemistry and explain its importance.
2. Describe the difference between electrolytic and galvanic (voltaic) cells.
3. Write half-reactions and overall cell reactions.
4. Calculate standard electrode potentials and predict the direction of electron flow.
5. Understand practical applications of electrochemistry in everyday life.
Lesson Outline / Brief Notes:
1. Introduction to Electrochemistry (10 minutes)
Definition: Electrochemistry is the branch of chemistry that deals with the relationship between chemical reactions and electricity.
Key Concept: Redox reactions involve the transfer of electrons.
Real-life example: Batteries, electroplating, corrosion prevention.
2. Galvanic (Voltaic) Cells (15 minutes)
Composed of two half-cells connected by a salt bridge.
Oxidation occurs at the anode, reduction at the cathode.
Example: Daniell cell
Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s)
Oxidation: Zn → Zn2+ + 2e−
Reduction: Cu2+ + 2e− → Cu
3. Electrolytic Cells (10 minutes)
Require an external power source to drive non-spontaneous reactions.
Example: Electrolysis of molten NaCl
At cathode: Na+ + e− → Na
At anode: 2Cl− → Cl2 + 2e-
4. Standard Electrode Potentials (10 minutes)
Electrode potential measures the tendency of a species to be reduced.
Example:
Zn2+/Zn: -0.76 V
Cu2+/Cu: +0.34 V
Predict electron flow: Electrons flow from Zn to Cu in a Daniell cell.
5. Applications of Electrochemistry (5 minutes)
Batteries (Li-ion, lead-acid)
Electroplating (silver plating, chromium plating)
Corrosion protection (galvanization)
Exercise (10 minutes)
1. Short Answer Questions:
a. Define electrochemistry.
b. Identify the anode and cathode in a zinc-copper galvanic cell.
c. Explain the difference between galvanic and electrolytic cells.
2. Calculation:
Given:
Zn2+/Zn: -0.76 V
Cu2+/Cu: +0.34 V
Calculate the standard cell potential of a Daniell cell.
3. Application Question:
Describe one practical application of electrochemistry in everyday life and explain how it works.
These courses provide students with a broad and engaging foundation in Science, covering Biology, Chemistry, and Physics. In Biology, learners investigate the structures, functions, and interactions of living organisms and their environments. Chemistry lessons focus on the composition, properties, and reactions of substances, helping students understand the building blocks of matter and the changes it undergoes. Physics explores the fundamental principles of energy, motion, and forces that shape the physical world. Through a balance of theory, practical experiments, and problem-solving activities, students develop critical thinking, analytical skills, and a deeper appreciation of how science explains and influences everyday life.
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