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Sci 7- Unit 3- Topics 1-2-3
Transcript of Sci 7- Unit 3- Topics 1-2-3
Topic 1- Using Energy from Heat
Energy in the form of HEAT
We use Thermal energy to cook food and stay warm
Let's look how we have cooked food over the years
OPEN FIRES- messy, unsafe
Modern stoves- easy to control
Now let's look at how heating has changed...
it all began with open fires...
allows us to control the heat
We even use
the sun to heat
Houses are even designed to keep in heat.
From igloos (made of Ice),
Sod houses (Made of Soil),
New modern homes (Made of wood products).
Topic 2- Measuring Temperature
This can be done by using our senses:
Touch (your skin can detect changes in temperature)
Sight (the color of the material giving off heat)
A relative idea about temperature is that it tells you how hot or cold something is.
Relative ways to determine the temperature are not always reliable or safe.
The Italian scientist Galileo invented the first air thermometer around 1600 and it has, and will continue to be, improved upon.
The 1st precise scale was developed by Anders Celsius in 1742.
He used 'degree' as the unit of temperature.
All of his standards for comparison to make his markings (on his scale) were based on the properties of water.
0 was assigned the temperature at which ice melts at sea level
100 was assigned the temperature at which liquid water boils at sea level
reliable devices that measure temperature
USA- uses degrees Fahrenheit as their standard temperature measurement
Canada- uses degrees Celsius as their standard temperature measurement
The two fixed temperatures that Celsius chose can be used to calibrate a thermometer (p. 195)
The region between (above and below, as well) these two extremes was separated into 100 equal units (degrees)
Low pressure enables water to boil at a temperature below 100o. (On top of Mt. Everest, water boils at 69o)
Pressure also affects the freezing and boiling points of water.
Extremely high pressure can cause ice to melt at a temperature below 0
(Ice skaters actually glide on a thin layer of water)
Absolute zero is the coldest possible temperature
- 273o and is used by scientists.
The Kelvin scale was developed by William Thomson
- a.k.a. Lord Kelvin -
and the markings on the scale are not called degrees,
but are simply called kelvins.
(0 Celsius is equal to 273.15 Kelvin)
The Right Device for the Job
(Read Pages 199-200-201)
A RESPONDER - which indicates the data with a pointer, light or other mechanism using the signal
Measuring different extremes of temperatures means using different types of devices to measure these extremes.
The thermometers used for this purpose have:
A SENSOR -
a material which is affected by changes in some feature of the environment, such as temperature
A SIGNAL - provides information about the temperature, such as an electric current
4 TYPES OF TEMPERATURE DEVICES
The Bimetallic Strip
The Recording Thermometer
The Infrared Thermogram
When heat is applied to one end an electric current is produced.
This current can turn on and off a switch or valve.
Two wires of different metals are twisted together.
A bimetallic strip is made of two different metals joined (fused) together, often formed into a coil.
When heat is applied to the end, one of the metals will expand faster than the other and the coil can operate a switch or valve just as the thermocouple does.
When a bimetallic coil strip is attached to a long arm lever, with a marker at the end and a drum that has graph paper, a recording thermometer can be made.
The infrared radiation can be photographed with special films or detected by special sensors that display colored images.
The brightness or color of the image indicates the temperature of the object.
Topic 3- The Particle Model, Temperature, and Thermal Energy
The Particle Model of Matter is a scientific description of the tiny particles that make up all things.
The key elements in this model are:
All substances are made of tiny particles too small to be seen
The particles are always in motion
The particles have spaces between them
Three States of Matter are?
Particles are closely packed together
Particles can slip past each other
Particles have lots of space between them
Temperature and the Particle Model
When heat is added to a substance, the particles move faster.
When heat is lost from a substance the particles move slower.
What is Energy?
Energy is the measure of a substance's ability to do work
- or cause changes.
Energy is always transferred in the same direction
What Energy is ? and is NOT
Energy gives it the ability to move, do work or cause change.
Energy is not a substance. It cannot be seen, weighed or take up space.
It can only be transformed from one type to another.
The Law of Conservation of Energy
The motion of the particles increases when the temperature increases.
The motion of the particles decrease when the temperature decreases
Temperature indicates the average energy (speed) of the particles in motion in a substance.
can anyone define
Energy right now???
There are two important elements that occur:
Changes happen when there is a difference of energy
Example: from a high-energy source (hot) to something of lower energy (cold).
The temperature of any substance is affected when heat is transferred.
The change in temperature depends on the number of particles affected.
Don't forget this
Energy cannot be created or destroyed.
Think of a volleyball Player, Where does the energy go from the hand when it strikes the ball?
Energy is a condition or quality that a substance has.
a silly song on what the types of energy there are...
Topic 1-2-3 Wrap-up
p.209: Questions 1, 2, 4, 9