Matter and Energy When Matter and energy interact changes in matter occur.
Energy How does matter interact with energy?. Definitions Energy is the ability to do work Work...
-
Upload
leon-cummings -
Category
Documents
-
view
217 -
download
1
Transcript of Energy How does matter interact with energy?. Definitions Energy is the ability to do work Work...
Energy
How does matter
interact with energy?
Definitions
Energy is the ability to do work Work means that a mass must be moved by a
force against it
Mechanical energy Energy of macroscopic systems (large enough to
be seen by the naked eye)
Nonmechanical energy Energy of microscopic systems (too small to be
seen by the naked eye
Mechanical Energy
Potential energyStored energyWound-up springStanding at the top of a cliff
Kinetic EnergyEnergy of motionRelaxing springFalling off a cliff
Nonmechanical Energy
Electrical energy Energy of moving electrons
Chemical energy Energy stored in chemical compounds
Sound energyMagnetic energy Energy in magnetic fields
Electromagnetic “radiant” energy Cosmic rays to TV
Heat energyActivation Energy The energy required to start a chemical reaction
Conservation of Mass and Energy
In any chemical or physical change, matter and energy are neither created nor destroyed.
Atoms are rearranged
Energy is converted to one form or another
Mass and Energy are interchangeable
Energy Conversion-The Car (simplified)
Chemical potential energy is stored in the battery. As you turn the key, the potential energy is converted to kinetic electrical energy and flows to the starter motor and coil.The electrical energy is converted to mechanical energy as the starter motor gears turn the flywheel, crankshaft, and camshaft(s).The camshaft lobes transmit this energy to the fuel pump and coil. The coil uses magnetic energy to increase voltage of the electrical energy.Fuel is mixed with air, compressed, and ignited (activated) by an electrical spark from the coil. The potential energy of the fuel is converted to mechanical energy as the gaseous products of the reaction expand to force the pistons. This mechanical energy eventually turns the transmission gears, drive axles, and wheels.
Energy and Chemical Reactions
In any chemical reaction, there is a difference in energy between the reactants and products
If products have greater energy (absorbed) reaction is ENDOTHERMIC
If products have lesser energy (released) reaction is EXOTHERMIC
The formation of new substances is always exothermic
Chemical Equations
Reactants yield products
2H2 + O2 2H2O + energy (exothermic)
2H2O + energy 2H2 + O2 (endothermic)
Left of arrow are reactants
Right of arrow are products
Endothermic or Exothermic?
Combustion (Burning) of fuel like gasoline or natural gas Potential chemical energy of the fuel is liberated EXOTHERMIC
Thawing of ice Energy is absorbed by the ice to “unlock” the
molecules from crystal lattice ENDOTHERMIC
Heat vs. Temperature
Heat One of many forms of energyMeasured in Joules (J) or calories (cal)
TemperatureThe average kinetic energy of a systemMeasured in degrees Celsius (°C),
degrees Fahrenheit (°F) or Kelvins (K)
The Fahrenheit Scale
Used popularly in some countries, like the USA
To convert from °F to °C
(°F-32) x 5/9 (be sure to subtract first)
To convert from °C to °F
°C x 9/5 +32
Conversion Problems
What is the normal average human body temperature in °C?
(98.6 -32) x 5/9 =
37.0 °C
What is the boiling point of water in °F?
100 x 9/5 +32 =
212 °F
Convert -40 °F to °C
(-40 -32) x 5/9 =
-40 °C
The Kelvin Scale
Starts at absolute zero (0K)
Note: we do not use the degree symbol (°) when reporting temperature in Kelvins
Each Kelvin is the same size as a Celsius degree.
To convert to K, add 273 (K= °C + 273)
To convert to °C, subtract 273 (°C= K-273)
Conversion Problems
What is the boiling point of water in K?100°C + 273 = 373KNitrogen boils at –196°C. What is this temperature in K?-196 + 273 = 77KEven something extremely “cold” contains heat!!!
More conversion problems
In Kelvins, normal human body temperature is 310K. What is this temperature in °C?
310 - 273
= 37°C
The average surface temperature on Pluto is 44K. What is this temperature in °C?
44 – 273
= -229°C