Boyles Law A law stating that the pressure of a given mass of
an ideal gas is inversely proportional to its volume at a constant
temperature.
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2. A gas law stating that the pressure and volume of a gas have
an inverse relationship when temperature is held constant. 3. If
pressure increases, then volume ____________________and vice versa,
when temperature is constant.
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According to this law, the pressure exerted by a gas held at a
constant temperature varies inversely with the volume of the gas.
For example, if the volume is halved, the pressure is doubled; and
if the volume is doubled, the pressure is halved. The reason for
this effect is that a gas is made up of loosely spaced molecules
moving at random. If a gas is compressed in a container, these
molecules are pushed together; thus, the gas occupies less volume.
The molecules, having less space in which to move, hit the walls of
the container more frequently and thus exert an increased
pressure.
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http://en.wikipedia.org/wiki/Boyle%27s_law
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Practice Problem A balloon was inflated to a volume of 5.0
liters at a pressure of 0.90 atm. It rises to an altitude where its
volume becomes 25.0 liters. Will the pressure around the balloon
increase or decrease? What was the new pressure?
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Practice Problem A fountain pen which has a total volume of 2.4
cm3 is half full with ink at the surface where the pressure is
780.0 mmHg. It is put in a pilot's pocket who flies to an altitude
where the pressure is 520.0 mmHg. How much ink leaks out of the
pen?
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Plasma! Plasma has neither a definite volume nor a definite
shape. Plasma often is seen in ionized gases. Plasma is distinct
from a gas because it possesses unique properties. Free electrical
charges (not bound to atoms or ions) cause plasma to be
electrically conductive. Plasma may be formed by heating and
ionizing a gas.
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Example Stars are made of plasma. Lightning is plasma. You can
find plasma inside fluorescent lights and neon signs.
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*Charles Law 1. Charles's law (also known as the law of
volumes) is an experimental gas law which describes how
_____________tend to ______________when heated. 2. At constant
pressure, the volume of a given mass of an ideal gas increases or
decreases by the same factor as __________________on the absolute
temperature scale (i.e. the gas expands as the temperature
increases)
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3. The physical law that the volume of a fixed mass of gas held
at a constant pressure varies ____________________with the absolute
temperature 4. What kind of relationship?
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Application/Examples A container holds 50.0 mL of nitrogen at
25 C and a pressure of 736 mm Hg. What will be its volume if the
temperature increases by 35 C?
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A sample of helium has a volume of 521 dm3 at a pressure of 75
cm Hg and a temperature of 18 C. When the temperature is increased
to 23 C, what is the volume of the helium?
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Imagine a balloon filled with helium on a cold winter day.
While you are in the shop, the balloon is normal. As you step
outside the balloon begins to shrivel up. This happens because of
the temp. of the helium in the balloon deceases and becomes less
dense, because the helium particles lose energy and become more
concentrated, decreasing the volume. But when you put the balloon
in a warm area, it goes back to its original size
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Bell Ringer Which of the laws that we have discussed applies to
the diagram on the next slide?
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Magnetism! Some materials can be made into permanent magnets
Examples: Lodestones (magnetic all the time) Any piece of iron can
be changed into a permanent magnet through conduction Magnets exert
a ______________ force on each other
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Magnetic Pole An area of a magnet where the magnetic force
appears to be the______________. Magnetic Field: a region where a
magnetic force can be detected Application: Compasses used to
analyze magnetic fields and determine direction
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Earths Magnetic Field Works like a bar magnet Has north and
south poles Source of magnetic field is still being debated
Magnetic poles not the same as geographic poles.
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Section 2: Magnetism from current! Electric currents can
produce magnetic fields The magnetic field of a coil of wire
resembles that of a bar magnetic Solenoid!
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Solenoid A long, wound coil of insulated wire When attached to
current a magnetic field is created More loops or more current =
stronger magnetic field
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Electromagnet A strong magnet created when an_____________ core
is inserted in to the center of a current carrying solenoid The
solenoid magnetizes the iron rod. The iron rod increases the
magnetic field of the solenoid.
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Electromagnetic Devices Galvanometer: an instrument that
measures the amount of current in a circuit. Electric Motor: A
device that converts electrical energy into ________________
energy. A motor uses magnets to create motion. Stereo Speakers: use
magnetic force to produce____________
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Electric motor
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Electric Currents from Magnetism Electromagnetic Induction: the
production of current in a conducting circuit by a ______________in
the strength, position, or orientation of external magnetic field.
* an electric current can be produced in a circuit by changing a
magnetic field*
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Electromagnetic Induction As a loop of wire moves in and out of
a magnetic field, a current is_____________.
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Generators A device that uses electromagnetic induction to
convert mechanical energy to ______________energy. Opposite of
.
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Alternating Current: an electric current that changes direction
at regular intervals. Application: Generators used at home are AC,
current supplied to home outlets DC= Direct current. One Direction
for the pathway.
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Transformers A device that can change one alternating current
voltage to a different alternating current voltage. Transformers
can increase or decrease voltage