INTRODUCTION TO ENERGY AND
CHEMISTRY
What is Energy?
it is the ability to do work, if an object or organism does work they use energy
Types of Energy
Heat
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internal motion of atoms, caused by friction
causes change in temperature and phase in any form of matter
ex. rubbing of hands, rubbing of stones by ancestors to create fire
Chemical
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breaking or making chemical bonds of atoms, specifically electrons
energy is released when bonds are broken
ex. fuel, food, wood, batteries and fossil fuels
2 Types of Chemical Reaction
Endothermic - chemical reactions that absorb energy from the surroundings
ex. ice packs
Exothermic - chemical reactions that release energy to the surroundings
ex. fireworks
Electrical
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motion of electric charges
specifically when electrons get pulled from positive charges and forced into a conductor
Electromagnetic
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energy through waves
all the wavelengths in the electromagnetic spectrum carry electromagnetic energy
light energy is a form of electromagnetic energy
ex. xrays for medical purposes
infrared for thermal cameras
Nuclear
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fission or fusion of atoms, specifically the atom's nuclei or nucleus
energy is released when the nucleus splits (fission), also when nuclei collide at high
speeds and join (fusion)
ex. stars - energy is formed from the hydrogen nuclei fusing to create helium nuclei,
when fuel runs out the star dies
Mechanical
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motion of an object, which is the sum of its kinetic energy and potential energy
it happens when work is done in an object
ex. kicking a football
ENERGY TRANSFORMATION AND
CONSERVATION OF ENERGY
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energy can be changed from one form to another.
these changes are called energy conversions
ex. rubbing of hands - mechanical energy to heat energy eating food - chemical to
mechanical blender - electrical to mechanical light bulb - electrical to light nuclear power
plants - nuclear to electrical
First law of thermodynamics: the law of conservation of energy states that energy can neither be
created nor destroyed, and can only be transferred between system and surroundings
HEAT AND WORK
THERMODYNAMICS
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deals with all kinds of energy effects in all kinds of processes
it distinguishes between two types of energy, heat (q) and work (W)
Heat (q) describes the transfer of thermal energy caused by a difference in temperature. It is
measured in Joules (J) since it's considered a movement of energy.
Work (W) done by a constant force on an object is defined as the product of the component of
the force along the direction of displacement and the magnitude of the displacement. It is
represented by the formula below:
W = F x d or W = (F cos θ)Δx
under the branch of Thermodynamics is...
THERMOCHEMISTRY
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refers to the study of the heat flow that accompanies chemical reactions
it also focuses on the study of the heat given off in a chemical reaction
Heat flow is the movement of heat from one body to another.
METHODS OF HEAT TRANSFER
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Conduction - occurs between objects that are touching each other ex. touching a stove
Convection - motion of fluid driven by temperature differences across that fluid
fluids are either liquids or gases
ex. hot air rising, and cool air sinking
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Radiation - occurs without the movement of matter ex. heat from sun ex. heat from
lightbulb ex. heat from a fire ex. heat from anything else that is warmer than the
surroundings
HEAT FLOW
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system and surroundings
system is that part of the universe on which attention is focused
surroundings is essentially the rest of the universe
ex. a glass of cold water, glass of the water is the system and the air around it the
surroundings
next week's topic:
Heat capacity and Calorimetry