Transcript Heat and Thermometer

Heat and
Thermometer
ELED 4312
Science Content
Contents
• Why do we need thermometer?
• How does a thermometer work?
• Change of Matter
• Kinetic theory
• Heat Energy
• Heat Transfer
• Scales of Temperature
If there is a no thermometer…
“How hot is he?”
“I don’t know”
“How cold is
there?”
“Here is not cold..
I feel pretty hot…”
Thermometer
• A thermometer is a device that
measures the temperature of things.
• To measure the temperature with a
particular scale in order for others to
understand the degree of
temperature exactly.
How does a thermometer work?
Hot weather!
High temperature!
Cold weather!
Low temperature!
The Function of Thermometer
• Thermometers rely on the simple
principle that a liquid changes its
volume relative to its
temperature.
Low
temperature
Liquids
(mercury or alcohols)
Volume decreases!
High
temperature
Volume increases!
Change of Matter State
Heat Energy
Particles
of matters
Heat Energy
Kinetic theory of matter
• All matter is made up of atoms and molecules
that are constantly moving.
• The motion and spacing of the particles
determines the state of matter of the substance.
• When heat is added to a substance, the
molecules and atoms vibrate faster. Solids,
liquids and gases all expand when heat is added.
When heat leaves all substances, the molecules
vibrate slower.
• Mass of the object remains the same.
“Law of Conservation of Mass”
Heat makes
the state of matter change!
In general,
the volume of matters increase except water!
Change of State of Matter:
Physical Change
• A physical change does not produce
a new substance.
• Changes in state or phase (melting,
freezing, vaporization, condensation,
sublimation) are physical changes.
• Examples of physical changes include
crushing a can, melting an ice cube,
and breaking a bottle.
What is Heat Energy?
• The heat energy of a substance is determined
by how active its atoms and molecules are.
• A hot object is one whose atoms and molecules
are excited and show rapid movement. A cooler
object's molecules and atoms will be less excited
and show less movement.
• When these atoms and molecules are in the
excited state, they take up a lot of space because
they're moving around so fast. When the atoms
and molecules settle down, or cool down, they
take up less space.
Heat Transfer
• Heat travels from a hot object to a cold object.
Conduction
• Conduction is the transfer of thermal
energy through direct molecular
communication in direct physical contact.
• Conduction is greater in solids, where
atoms are in constant contact. Liquids and
gases are not good conductors.
Convection
• transfer of heat by convection in a moving
medium, such as a fluid or gas.
Heated air rises, cools, then
falls. Air near heater is
replaced by cooler air, and
the cycle repeats.
Hot water rises
And Cool falls
Air above warmer
Ground rises.
Radiation
• Transfer of heat by electromagnetic
radiation or, equivalently, by photons.
• All materials radiate thermal energy in amounts determined by
their temperature, where the energy is carried by photons of light.
white reflects
radiant energy
better than
black.
Absorption and Emission of Radiation
Scales of Temperature
• Fahrenheit scale
- Freezing Point of Water: 32 degrees Fahrenheit
- Boiling Point of Water: 212 degrees F.
• Celsius scale
- Freezing Point of Water: 0 degrees Celsius
- Boiling Point of Water: 100 degrees C.
• Kelvin Scale
- 0 Degrees of Kelvin: This is at minus 273.15
degrees Celsius (or -523.67 F)!
Temperature Conversion
• Celsius = (Fahrenheit – 32)*5/9
• Fahrenheit = (Celsius * 9/5)+ 32
• Kelvin = Celsius + 273
29. Which of the following statements
accurately describes what occurs as heat is
added to water and change it to steam?
A. The water molecules gain kinetic energy
and move faster and father apart.
B. The chemical bonds between the
hydrogen and oxygen atoms of the water
molecules break.
C. The water molecules cluster together to
form ring-shaped molecular structures.
D. The hydrogen and oxygen atoms of the
water molecules change in shape.
From the sample test of the TExES Preparation Manual
Reference Websites
• Rader’s CHEM4KIDS!
http://www.chem4kids.com/index.html
• How atoms and molecules are
affected by Heat
http://www.mansfieldct.org/schools/mms/staff/han
d/atomsheat.htm
• How Things work!
http://www.energyquest.ca.gov/how_it_works/ther
mometer.html