Water Temperature & Heat Measurement – Physics
This chapter covers water temperature and heat measurement of physics.
change of a known mass of water
The amount of heat transferred can be determined by measuring the the temperature
calorie
The most commonly used unit for heat
to raise the temperature of 1 gram of water by 1 degree C
The calorie is defined as the amount of heat required
The kilocalorie
is 1000 calories ( the heat required to raise the temperature of 1 kilogram of water by 1 degree C)
Expansion of water
When water becomes ice, it expands. Ice has open-structured crystals resulting from strong bonds at certain angles that increase its volume. This make ice less dense than water.
Bimetallic Strip
Two, two strips of different metals welded or riveted together. because the two substances expand at different rates when heated or cooled, the strip bends; used in thermostats
Calorie
A unit of heat measurement used in nutrition to measure the energy value of foods. A calorie is the amount of heat energy needed to raise the temperature of 1 kilogram of water 1°C.
calorie
Amount of energy needed to raise temperature 1 gram of water 1 degree C
Degrees
A unit division of temperature.
Expansion Joints
separation joints in concrete and other things that allow the concrete to expand and contract
“Kilo”calorie
A unit of energy equal to 1,000 calories
Temperature
A measure of how hot (or cold) something is; specifically, a measure the measure of the average translational kinetic energy per particle in a substance.
Temperature
Quantity that tells how hot or cold something is
Matter expands
When temperature increases
Matter contracts
When temperature decreases
Temperature
is related to random motions of molecules in a substance
Temperature
is not a measure of total kinetic energy
Celsius Scale
The gap between freezing and boiling is divided into 100 equal parts, called degrees. This temperature scales is the
Water freezing
0 degrees Celsius
Water boiling
100 degrees Celsius
Fahrenheit scale
the temperature scale used commonly in the United States
Water freezing
32 degrees Fahrenheit
Water boiling
212 degrees Fahrenheit
Kelvin scale
the scale used in scientific research is the SI scale
absolute zero
0 kelvin
no kinetic energy to give up
At absolute zero a substance has
-273 Celsius
Zero on the Kelvin scale or absolute zero
1 liter
There is twice as much kinetic energy in 2 liters of boiling water as in
same
The temperature of both liters of water (the 2 boiling vs 1 not) are the same because the average kinetic energy of molecules in each is the
a warmer substance to a cooler substance
direction of spontaneous energy transfers is always from a
heat
energy that transfers from one object to another b/c of a temperature difference
heat
Matter contains energy in several forms but it does not contain
internal energy
thermal energy- the energy resulting from heat flow
thermal contact
When heat flows from one object or substance to another it is in contact with the objects or substances are said to be
flows from higher temperature into lower temperature
during thermal contact heat
average molecular kinetic energy difference
Heat flows based on
same temperature
After objects in thermal contact with each other reach the
thermal equilibrium
After object in thermal contact with each other reach the same temperature, no heat flows between them- we say the objects are in
only its own temperature
We then know the temperature of the thermometer is also the temperature of the substance. So a thermometer, interestingly enough, shows
internal movements of atoms within molecules
There is rotational kinetic energy of molecules and kinetic energy due to
there is also potential energy
due to force between molecules
internal energy
the grand total of all energies inside a substance
it contains internal energy
substances do not contain heat
Kilocalorie
The heat unit in rating foods is actually a __ although its often referred to as the calorie
caloric
heat was invisible and called
joules
heat is measured in, according the International System of Units
1 calorie equals 4.184 J
the relationship between calories and joules is that
joule equivalent
where an input of 4.184 joules raises the temperature of 1 gram of water 1 degree C
increases more
Although the same quantity of heat is added to both containers, the temperature of the container with the smaller amount of water increases more
released as heat
The energy value in food is determined by burning the food and measuring the energy that is
specified number of degrees
specific materials require quantities of heat to raise the temperature of a given mass of the material by a specified number of degrees
is responsible for increases in temperature
absorbed energy that increases the translation speed of molecules
increase the internal vibrations within molecules or stretch intermolecular
absorbed energy may also increase the rotation of molecules
Temperature
is a measure only of the kinetic energy of translation motion
translation fashion
iron atoms in the iron lattice primarily shake back and forth in
rotations, internal vibrations, and bond stretching
while water molecules soak up a lost of energy in
specific heat capactiy
water absorbs more heat per gram than iron for the same change in temperature, we say water has a higher
the specific heat capacity
of any substance is defined as the quantity of heat required to raise the temperature of a unit mass of the substance by 1 degree
thermal inertia
specific heat capacity is like___ since it signifies the resistance of a substance to change in its temperature
Water
has a much higher capacity for storing energy than most common materials
water is a very useful cooling agent
a relatively small amount of water absorbs a great deal of heat for a correspondingly small temperature rise, because of this
its temperature would rise higher for a comparable absorption of heat
If a liquid of lower specific heat capacity were used in cooling systems
water
takes longer to cool
improves the climate
the property of water to resist changes in temperature
water is warmer than the air
in the winter
water is cooler than air
in the summer
expansion
when the temperature of a substance is increased its molecules jiggle faster and normally tend to move farther apart
expand
solids, liquids, and gases _____ when they are heated and contract when they are cooled
gases
generally expand or contract much more than liquids
liquids
expand or contract more than solids
expansion
of materials must be allowed for in the construction of structures and devices of all kinds
Kelvin
0 K for Absolute Zero to 373 K for boiling point of water
– 0 at absolute zero; same size degrees as Celsius scale
– Kelvins, rather than degrees, are used
Heat
Internal energy transferred from one thing to another due to a temperature difference
•Internal energy in transit
Quantity of heat
Measured in joules or calories
4.18 joules of heat are required to change the temperature of 1 gram of water by 1 Celsius degree. 4.18 joules = 1 calorie
Energy ratings of foods and fuels are determined
from energy released when they are burned.
Unit of energy
US Customary System: Calorie or calorie, Metric: Joule
Specific heat capacity
Defined as the quantity of heat required to change the temperature of a unit mass of the substance by 1 degree Celsius
Thermal expansion
Due to rise in temperature of a substance, molecules jiggle faster and move farther apart.
Most substances expand when heated and contract when cooled.
Thermal Contact
state of two or more objects or substances in contact such that heat can flow from one to the other
Thermal Inertia
Tendency of a substance to resist change in temperature with the gain or loss of heat energy.
Thermal Equilibrium
The state of two or more objects or substances in thermal contact when they have reached a common temperature.
Thermostat
a regulator for automatically regulating temperature by starting or stopping the supply of heat. A common example of using a bimetallic strip
Absolute Zero
The lowest possible temperature that a substance may have – the temperature at which molecules of the substance have the minimum kinetic energy. Temp equal to 0K or -273°C
Internal Energy
The total of all molecular energies that are internal to a substance (Including Rotational, Vibrational and Translational Kinetic Energy)
bimetallic strip
brass expands or contracts more when heated or cooled than iron does so the strip bends as shown
thermostat
when the bimetallic coil expands, the mercury rolls away from the electrical contacts and breaks the circuit. when the coil contracts, the mercury rolls against the contacts and completes the electric circuit
Thermometer
Measures temperature by expansion or contraction of a liquid (mercury or colored alcohol)
Thermometer readings occur
when the thermometer and the object reach thermal equilibrium (having the same average kinetic energy per particle)
Celsius
scale named after Anders Celsius (1701 -1744).
-0C for freezing point of water to 100C for boiling point of water
Fahrenheit
scale named after G. D. Fahrenheit (1686-1736).
-32F for freezing point of water to 212F for boiling point of water