The document discusses enthalpy changes and exothermic and endothermic reactions. It defines exothermic reactions as reactions where heat energy is released to the surroundings, giving a negative enthalpy change. Endothermic reactions absorb heat from the surroundings, having a positive enthalpy change. Bond breaking requires energy and is endothermic, while bond forming releases energy and is exothermic. Whether a reaction is exothermic or endothermic depends on if more energy is released or absorbed during bond breaking and forming.
Topic Contains:
What is Thermo Chemistry ?
Define Origin of Heat of Reaction..
Exothermic Reaction..
Endothermic Reaction..
Graphical representation of Exothermic
and Endothermic reactions..
Different type of heat reactions..
Hess’s law..
Need of thermodynamics and the Laws of Thermodynamics.
Important principles and definitions of thermochemistry.
Concept of standard state and standard enthalpies of formations,
Integral and differential enthalpies of solution and dilution.
Calculation of bond energy, bond dissociation energy and resonance energy from thermochemical data.
Variation of enthalpy of a reaction with temperature – Kirchhoff’s equation.
Statement of Third Law of thermodynamics and calculation of absolute entropies of substances.
JFI -just for information
Topic Contains:
What is Thermo Chemistry ?
Define Origin of Heat of Reaction..
Exothermic Reaction..
Endothermic Reaction..
Graphical representation of Exothermic
and Endothermic reactions..
Different type of heat reactions..
Hess’s law..
Need of thermodynamics and the Laws of Thermodynamics.
Important principles and definitions of thermochemistry.
Concept of standard state and standard enthalpies of formations,
Integral and differential enthalpies of solution and dilution.
Calculation of bond energy, bond dissociation energy and resonance energy from thermochemical data.
Variation of enthalpy of a reaction with temperature – Kirchhoff’s equation.
Statement of Third Law of thermodynamics and calculation of absolute entropies of substances.
JFI -just for information
1. Understand that Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept: (a) Students know how to describe temperature and heat flow in terms of the motion of molecules (or atoms) and (b) Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants.
Thermodynamic laws describe the flows and interchanges of heat, energy and matter.
Almost all chemical and biochemical processes are as a result of transformation of energy.
Laws can provide important insights into metabolism and bioenergetics.
The energy exchanges between the system and the surroundings balance each other.
There is a hierarchy of energetics among organisms
The video lecture for this presentation is available at the following link on YouTube
https://youtu.be/3sxal579RNM
The presenation will be useful for Ug/PG (Chemistry) students
1. Understand that Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept: (a) Students know how to describe temperature and heat flow in terms of the motion of molecules (or atoms) and (b) Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants.
Thermodynamic laws describe the flows and interchanges of heat, energy and matter.
Almost all chemical and biochemical processes are as a result of transformation of energy.
Laws can provide important insights into metabolism and bioenergetics.
The energy exchanges between the system and the surroundings balance each other.
There is a hierarchy of energetics among organisms
The video lecture for this presentation is available at the following link on YouTube
https://youtu.be/3sxal579RNM
The presenation will be useful for Ug/PG (Chemistry) students
This is a summary of the topic "Energy changes" in the GCE O levels subject: Chemistry. Students taking either the combined science (chemistry/physics) or pure chemistry will find this useful. These slides are prepared according to the learning outcomes required by the examinations board.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
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June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
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The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Model Attribute Check Company Auto PropertyCeline George
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Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
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Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
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Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
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Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
1. Enthalpy Changes
Chapter 13
LEARNING OUTCOMES
Distinguish between exothermic and
endothermic reactions in terms of energy
content of products and reactants
Draw an energy profile diagram to illustrate
endothermic and exothermic change
Calculate energy changes from experiments
or experimental data
2. Exothermic reactions
When a piece of magnesium ribbon burns
in air or oxygen, heat and light energy are
produced.
This type of chemical reaction in which heat
energy is produced and given out to the
surroundings is called an exothermic change
or reaction.
An exothermic reaction is a reaction in which heat energy
is given out to the surroundings.
Enthalpy Changes
Chapter 13
3. Exothermic reactions
During an exothermic reaction,
the temperature of the
surroundings rises since heat
energy is given out by the
reaction.
Enthalpy Changes
Chapter 13
4. Other exothermic reactions
Freezing and condensation (physical changes)
Combustion of fuels
Neutralisation of acids and alkalis
Dissolving solid sodium hydroxide, anhydrous sodium
carbonate and anhydrous copper(II) sulphate in water
Adding water to concentrated sulphuric acid
Enthalpy Changes
Chapter 13
5. Endothermic reactions
An endothermic reaction is a
reaction in which heat energy is
absorbed from the surroundings.
In an endothermic reaction, the
temperature of the surroundings drops,
since heat energy is absorbed.
Enthalpy Changes
Chapter 13
When ammonium chloride crystals are dissolved in
water, there is a drop in temperature. This shows that
heat energy is absorbed from the surroundings.
6. Other Endothermic reactions
Melting and boiling (physical changes)
Thermal decomposition of compounds such as calcium
carbonate (limestone) and copper(II) carbonate
Photosynthesis
Taking a photograph with film (decomposition of
silver bromide into silver and bromine)
Dissolving ionic crystals in water, e.g.
dissolving ammonium nitrate, ammonium chloride and
sodium carbonate crystals in water
Enthalpy Changes
Chapter 13
7. Heat of Reaction
The amount of heat energy given out or taken in
during a chemical reaction is called the heat of reaction
or enthalpy change.
Enthalpy change is represented by the symbol, ∆H.
Matter contains both potential and kinetic energies. During
an exothermic reaction, heat is given out by the reactants
to the surroundings. Thus, enthalpy change is negative.
During an endothermic reaction, heat energy is absorbed
by from the surroundings. Reactants gain energy, so
enthalpy change is positive.
Enthalpy Changes
Chapter 13
8. Heat of Reaction
In an exothermic reaction, the
reactants are at a higher energy
level than that of the products.
The excess heat energy is given
out by the reactants when the
products are formed.
Since the reactants have lost
heat energy, we take ∆H as
negative.
Exothermic reaction
Enthalpy Changes
Chapter 13
9. Heat of Reaction
In an endothermic reaction,
the reactants are at a lower
energy level than that of
the products.
Heat energy is absorbed
by the reactants from the
surroundings in order to
change to the products. Endothermic reaction
Since the reactants have gained
heat energy, we take ∆H as
positive.
Enthalpy Changes
Chapter 13
10. Heat of Reaction
The negative value of ∆H means that the reaction is
exothermic.
“890 kJ” means that when 1 mole of methane burns completely
in oxygen, 890 kJ of heat energy is given out.
CH4(g) + 2O2(g) CO2(g) + 2H2O(l) [∆H = - 890 kJ]
The heat of reaction can be included in a chemical
equation as:
Enthalpy Changes
Chapter 13
11. Heat of Reaction
The positive value of ∆H means that the reaction is
endothermic.
“222 kJ” means that when 1 mole of calcium carbonate is
decomposed, 222 kJ of heat energy is absorbed.
CaCO3 CaO + CO2 [∆ H = + 222 kJ]
Enthalpy Changes
Chapter 13
12. Bond breaking and bond making
The reason why reactions are endothermic or
exothermic is because energy is taken in or given out
when chemical bonds are broken or made.
Heat energy is absorbed to break bonds, so bond
breaking is endothermic.
Enthalpy Changes
Chapter 13
13. Bond breaking and bond making
Heat energy is given out (released) when bonds
are formed, so bond forming is exothermic.
Enthalpy Changes
Chapter 13
14. Bond breaking and bond making
So, the overall heat change in a reaction is given by:
If more energy is absorbed for breaking bonds than
released in forming bonds, the reaction will be
endothermic.
If more energy is released in forming bonds than
absorbed for breaking bonds, the reaction will be
exothermic.
Heat of reaction, ∆H = Heat absorbed Heat given out
in bond breaking in bond forming
Enthalpy Changes
Chapter 13
15. Worked example
H
+
H
OH H O
H H
O
H H O
Since ∆H is negative, the overall reaction is exothermic.
Hydrogen burns in oxygen to form water according to the equation:
2H2(g) + O2(g) 2H2O (g)
By calculating ∆H, state whether the reaction will be endothermic or
exothermic, given the following bond energies per mole:
H-H = 436 kJ, O=O = 496 kJ, O-H = 463 kJ.
Solution:
Energy absorbed to break bonds = (2 x 436) + (1 x 496) = 1368 kJ
Energy released to form bonds = (4 x 463) = 1852 kJ
Hence, ∆ H = Energy absorbed – Energy released
= (1368 – 1852) kJ = - 484 kJ
Enthalpy Changes
Chapter 13
16. Summary
Exothermic reaction Endothermic reaction
Heat energy is given out to the
surroundings.
Heat energy is absorbed from the
surroundings.
∆H is negative. ∆H is positive.
More heat is given out in making
bonds than absorbed in breaking
bonds.
More heat is absorbed in breaking bonds
than given out in making bonds.
Enthalpy Changes
Chapter 13
17. Quick check
1. What is meant by (a) an exothermic reaction, (b) endothermic reaction?
2. What is meant by enthalpy change? What symbol is used to represent enthalpy
change?
3. What type of reaction is it when the enthalpy change ∆H is
(a) positive, (b) negative ?
4. Sodium hydroxide reacts with nitric acid according to the equation:
NaOH(aq) + HNO3(aq) NaNO3(aq) + H2O(l) ∆H = - 57.3kJ
(a) Is this reaction endothermic or exothermic? Explain your
answer.
(b) What would be the heat evolved if 2 moles of sodium
hydroxide are completely neutralised ?
5. State whether the following are exothermic or endothermic reactions:
(a) decomposing zinc carbonate,
(b) reacting potassium with water,
(c) forming hydrogen atoms from hydrogen molecules,
(d) forming chlorine molecules from chlorine atoms,
(e) respiration,
(f) photosynthesis.
Solution
Enthalpy Changes
Chapter 13
18. Solution to Quick check
1. (a) An exothermic reaction is a reaction which gives out heat energy to the
surroundings.
(b) An endothermic reaction is a reaction which absorbs heat energy from the
surroundings.
2. Enthalpy change is the amount of heat given out or taken in during a reaction.
The symbol used is ∆H.
3. (a) Endothermic (b) Exothermic
4. (a) The reaction is exothermic because ∆H is negative which means that heat
energy is lost from the reactants.
(b) Amount of heat evolved = 2 x 57.3 = 114.6 kJ
5. (a) decomposing zinc carbonate: endothermic
(b) reacting potassium with water: exothermic
(c) forming hydrogen atoms: endothermic
(d) forming chlorine molecules: exothermic
(e) respiration: exothermic
(f) photosynthesis: endothermic
Return
Enthalpy Changes
Chapter 13