Energy is the capacity to do work or to produce heat
-
Work- movement of object over a distance against resistance.
The Forms of Energy:
-
Radiant energy – example sunlight
-
Kinetic energy – energy of motion
o Includes mechanical energy –
energy in the moving parts of a machine
o Includes thermal energy –
random internal motion of particles of matter
-
Potential energy – energy possessed by objects because of their position or the arrangement of their particles
(stored energy)
o Includes gravitational potential
energy – held by objects due to their position
o Electrical Potential energy
– created when objects with opposite charges are separated.
o Chemical Potential energy –
exists because of the arrangement of the particles that make up a substance.
Measuring Energy
-
Common unit is the calorie (cal)
o 1 calorie is the amount of heat
needed to raise the temperature of 1 gram of water by 1 celcius degree
o 1 Cal
= 1000 cal (food measurement)
-
SI Unit: The Joule (James Prescott Joule 1818-1889
o 1 cal = 4.814 J
Law of Conservation of Energy
-
Joule proved that different forms of energy are equivalent, meaning that a particular amount of potential or
radiant energy can be converted into exactly equivalent amounts of kinetic energy.
-
Natural Law: law of conservation of energy – energy is neither created nor destroyed
The Energy Crisis:
-
Since energy cannot be created or destroyed, how is it possible that we are “running out of energy”/
-
We use fossil fuels- gasoline and coal- has lots of potential energy
2-2 Temperature:
-
Why can not the sense of touch be used to measure temperature?
-
A thermometer is an instrument that gives and accurate and precise reading of temperature.
-
Galileo Galilei (1564-1642) – invented the first temperature instrument
o Modern thermometers have a bulb
filled with mercury or colored alcohol attached to a stem
o Heating causes liquid to expand
and move up the stem
o Cooling causes liquids to condense
and move down the stem
The Fahreheit and Celsius Temperature Scales
-
Gabriel Fahrenheit- Made thermometers in the late 1600’s and early 1700’s- made up his own temperature
scale.
-
Anders Celsius (1701-1744) developed a scale much more in tune with the metric system
o Freezing point at sea level
= 0 Boiling point at seas level = 100
The Kelvin Temperature Scale
-
The SI scale used to measure temperature is the Kelvin Scale
-
Lord Kelvin (English- 1824-1907) : unit K
o A degree change of 1 K is the
same as a degree change of 1 C
o Zero point in the Kelvin scale
corresponds to absolute zero (-273 C)
§ Absolute
zero is where molecular motion stops
-
Some Equations
o C= K – 273
o K= C + 273
o (oF-32oF)
x (100oC/180oF) = oC
o (oC x 180oF/100oC)
+ 32oF = oF
2-3 Matter
-
Matter is the “stuff” of which things are made
o Has mass (amount of stuff) and
volume (amount of space)
-
Do not know where the “stuff” came from, but it is here and we have learned a lot about the “properties
of matter”
o Has been a philosophical issue
for millennia
States of Matter:
-
Four States of Matter:
o Solid
o Liquid
o Gas
o Plasma
-
Properties of the different states (generalized):
o Solid:
§ High
density
§ Density
affected little by changes in pressure
§ Shape
not affected by the shape of a container
§ Orderly
arrangement of particles (ie. Crystals)
o Liquid:
§ High
density
§ Density
affected little by changes in pressure
§ Adopts
the shape of the container
o Gas:
§ Low
density
§ Density
depends on the pressure
§ Expands
to fill the container
o Plasma
§ Low
density
§ Density
depends on pressure
§ Expands
to fill the container
§ Exists
only at high temperatures
Changes in State:
-
Can observe changes in states by heating or cooling a substance
Ex:
Water at 0 C is changing from liquid to solid
Water at 100 C is changing from liquid to gas
Water from 0 C to 100 C is in the form of a liquid
Ex
Mercury at –39 C is changing from a liquid to a solid
Mercury at 357 C is changing from a liquid to a gas
Mercury from –39 C to 357 C is a slippery liquid
Properties of Matter:
-
A sample of matter can be identified by observing its characteristics or properties
-
Physical Properties: properties that can be observed without changing the identity of the substance. (density/
color/ melting point, etc)
1) State:
(at standard temperature and pressure): Liquid, Solid, Gas
2) Quantity:
mass, volume, density
3) Color
4) Texture
5) Melting
and boiling points
6) Conductivity
7) Solubility
in Water
-
Chemical Properties: properties that cannot be observed without changing the identity of the substance (flammability,
etc)
1) Evolution
of a gas
2) Formation
of a precipitate
3) Absorb
or Gives off heat
4) Emission
of light
5) Color
Change
