High School
a. P3.p1 Conservation of Energy (prerequisite)
When energy is transferred from one system to another,
the quantity of energy before transfer equals the quantity
of energy after transfer. (prerequisite)
- Conservation
of Energy
The amount of energy remains constant and energy is
neither created nor destroyed. Energy can be converted
from one form to another (potential energy can be
converted to kinetic energy) but the total energy
within the domain remains fixed. This NASA site gives
an indepth explanation of the Conservation of Energy.
- Energy
Changes Make Things Happen
- This website does a good job of both providing
an overview of the energy transformations involved
in chemical, physical, and nuclear changes and it
provides links that allow you to investigate specific
types of energy transformations more thoroughly.
-
- The
Law of Conservation of Energy
Energy
in a system may take on various forms (e.g. kinetic,
potential, heat, light). The law of conservation
of energy states that energy may neither be created
nor destroyed. Therefore the sum of all the energies
in the system is a constant.
b. C3.1x Hess’s Law
For chemical reactions where the state and amounts of
reactants and products are known, the amount of energy
transferred will be the same regardless of the chemical
pathway. This relationship is called Hess’s law.
- Calorimetry
Tutorial
This tutorial demonstrates how a bomb calorimeter
works, and walks through the equations used to solve
calorimetry problems. Includes an interactive experiment..
- Change
in Enthalpy Example Problems This page
provides exercises in the use of thermochemical equations.
To produce a problem, click on the "New Problem"
button in the main frame and a question will appear
in the top frame. There are also an answer cell and
a "Check Answer" button in the top frame.
Determine the value of the answer, enter it in the
cell and press the "Check Answer" Button.
- Hess's
law
Hess' Law is a law of physical chemistry named for
Germain Hess's expansion of the Hess Cycle, used to
predict the enthalpy change and conservation of energy
(denoted as state function ?H) regardless of the path
through which, it is to be determined.
- Hess's
Law Example Problems
This page is an exercise in using Hess' Law. When
you press "New Problem" a reaction set with
a single missing enthalpy will be displayed. Calculate
the needed enthalpy, enter it in the cell and press
the "Check Answer" button. The results will
appear in the table on the main page. This page is
complex, but it's not intended to be tricky. Thus,
no attempt has been made to mislead you. There should
be a straightforward combination of the contributing
reactions which yields the desired reaction.
- Hess's
Law Lab
This lab can be used to reinforce both concepts involving
exothermic reactions and Hess's Law.
- Hess's
Law Tutorial
This tutorial explains Hess's law of constant heat
of summation using animated sample problems and step-by-step
descriptions. Includes practice exercises.
- Hess's
Law Worksheet
This is a worksheet with example Hess's Law problems
that can be used to reinforce the concept.
c. P3.p2 Energy Transfer (prerequisite)
Nuclear reactions take place in the sun. In plants,
light from the sun is transferred to oxygen and carbon
compounds, which, in combination, have chemical potential
energy (photosynthesis). (prerequisite)
- Energy
Transfer
When you turn on a light, you see result of energy
being transferred from the sun to the plants to the
coal to electricity and finally to light you see.
During each of these transfers, energy changes form.
- What
Type of Energy is it?
This site explores the question: "How many different
types of energy are there?" There are even links
to energy conservations in nature and photosynthesis.
d. C3.2x Enthalpy
Chemical reactions involve breaking bonds in reactants
(endothermic) and forming new bonds in the products
(exothermic). The enthalpy change for a chemical reaction
will depend on the relative strengths of the bonds in
the reactants and products.
- Enthalpy
- Definition
From Wikipedia, the free encyclopedia a definition
of enthalpy.
- Enthalpy
Change
The heat content of a chemical system is called the
enthalpy (symbol: H). The enthalpy change (H) is the
amount of heat released or absorbed when a chemical
reaction occurs at constant pressure. This site does
a nice job of explaining enthalpy change.
e. C3.3 Heating Impacts
Heating increases the kinetic (translational, rotational,
and vibrational) energy of the atoms composing elements
and the molecules or ions composing compounds. As the
kinetic (translational) energy of the atoms, molecules,
or ions increases, the temperature of the matter increases.
Heating a sample of a crystalline solid increases the
kinetic (vibrational) energy of the atoms, molecules,
or ions. When the kinetic (vibrational) energy becomes
great enough, the crystalline structure breaks down,
and the solid melts.
- Basic
Terminology and Concepts
There are many forms of kinetic energy - vibrational
(the energy due to vibrational motion), rotational
(the energy due to rotational motion), and translational
(the energy due to motion from one location to another).
This site demonstrates the nature of kinetic energy.
- Conduction
of Heat in Metals and Non-metals
This site has an animation showing how heat is conducted
from one atom to another in both non-metals and (if
you click "next") metals.
- Melting
Animation The following link takes you
to a short movie that shows the melting of an ice
cube from the submicroscopic level. It indicates the
hydrogen bonds that are being broken, allowing the
solid particles to move further apart and progress
to the liquid phase.
f. C3.3x Bond Energy
Chemical bonds possess potential (vibrational and rotational)
energy.
- Bond
Energy
For any particular chemical bond, say the covalent
bond between hydrogen and oxygen, the amount of energy
it takes to break that bond is exactly the same as
the amount of energy released when the bond is formed.
This value is called the bond energy. The site gives
several examples of the energy necessary to break
bonds in molecules.
- What
is Bond Energy?
This site has an interactive animation that students
can use to explore bond energy. In the activity move
the sliders to find the amount of energy needed to
break the bonds in the hydrogen and chlorine molecules
changing them into free gaseous atoms.
g. C3.4 Endothermic and Exothermic Reactions
Chemical interactions either release energy to the environment
(exothermic) or absorb energy from the environment (endothermic).
- Endothermic
and Exothermic Laboratory This site
contains directions and a student data table for completing
a lab concerning endothermic and exothermic reactions.
- Endothermic
and Exothermic Reactions
- This website focuses on the types of energy transformations
involved in chemical changes. It explains the difference
between endothermic and exothermic reactions. In
addition, it provides the directions for a laboratory
activity which will allow the students to compare
an endothermic reaction to an exothermic reaction.
- Thermochemistry Simulations New
Heat of neutralization
simulation experiment reacting an acid with a base
in a calorimeter. Many other simulations are also
included.
h. C3.4x Enthalpy and Entropy
All chemical reactions involve rearrangement of the
atoms. In an exothermic reaction, the products have
less energy than the reactants. There are two natural
driving forces: (1) toward minimum energy (enthalpy)
and (2) toward maximum disorder (entropy).
- Bond
Enthalpy
The Bond Enthalpy is the energy required to break
a chemical bond. The site gives a detailed explanation
of bond breaking and bond formation.
- Chemical
Thermodynamics
Changes in energy -- however measured, whether it
be heat, light, work, etc. -- are clearly physical
events that also have a chemical nature to them. Five
topics related to energy are discussed here.
- Energy,
Entropy, Enthalpy
The science of thermodynamics is founded on
two principles, both of which involve the concept
of energy. This site explores these two principles.
- Entropy
Tutorial This tutorial includes an "Entropy
Battle" game which challenges you to maintain
order within a system as the temperature rises and
the phase level moves from solid to gas. Concludes
with practice exercises.
- Estimating
Enthalpy Changes Tutorial
Learn how to use average bond energies to estimate
the energy released during a combustion reaction.
Includes practice problems.
i. C3.5x Mass Defect
Nuclear reactions involve energy changes many times
the magnitude of chemical changes. In chemical reactions
matter is conserved, but in nuclear reactions a small
loss in mass (mass defect) will account for the tremendous
release of energy. The energy released in nuclear reactions
can be calculated from the mass defect using E = mc2.
- Energy
Changes Make Things Happen
- This website does a good job of both providing
an overview of the energy transformations involved
in chemical, physical, and nuclear changes and it
provides links that allow you to investigate specific
types of energy transformations more thoroughly.
- Mass
Defect
This site has a series of slides that show an example
of mass defect.
- Mass
Defect
This is an animation that explains and demonstrates
that in nuclear reactions energy is released.
- Radioactive Decay Lab New
This is a lab with insructions
that can be downloaded and copied or used directly
by students in the chemistry lab. It is a good review
of radioactive decay and a hands on visual of what
occurs at the atomic level. This lab would also be
good for a physical science class.
- The
Mass Defect
This site discusses the explanation and the consequences
of the mysterious missing mass in a nuclear reaction.
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