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Copy of Sci 7- Unit 3- Topics 1-2-3
Transcript of Copy of Sci 7- Unit 3- Topics 1-2-3
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 Pioneer Stoves-
stoves Modern stoves- easy to control
and convenient Now let's look at how heating has changed... Once again, it all began
with open fires... Modern technology
allows us to control the heat We even use
the sun to heat
Solar Heating Other ways
Heat.... Houses are even designed to keep in heat.
From igloos (made of Ice) Topic 2- Measuring Temperature To tell how hot or cold something is, we could use 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 first 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 Anders Celsius USA- uses degrees Fahrenheit as their standard temperature measurement Canada (and many other countries)- 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) CRAZY FACTS 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
- 273.15 oC 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 To measure different extremes of temperature, we must use different devices. 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 Thermocouple 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 a 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. 7 seconds 35 seconds 53 seconds 42 seconds 1:39 minutes 45 seconds 58 seconds 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 - vibrating, rotating, and (in liquids and gases) moving from place to place. The particles have spaces between them. 52 seconds Review-
Three States of Matter are? Solid Liquid Gas 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 an object or substance's ability to move, do work, or cause changes. Energy is always transferred in the same direction, from high-energy to low-energy What Energy is ? and is NOT Energy is a property or quality of an object or substance that 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, or passed from one object, or substance 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 speed (energy) of the particles in motion in a substance. Seriously...
can anyone define
Energy right now??? For changes in energy, here are 2 important points. Changes happen when there is a difference of energy Example: When you boil water on the stove. Energy from the stove is transferred to the pot, and then to the water. Thermal Energy and Temperature Changes The temperature of any substance is affected when heat is transferred.
The change in temperature depends on the number of particles affected. Important Don't forget this Remember 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... Sod houses (Made of Soil), New modern homes (made of
wood products). Can you think of others? The thermal energy of a substance depends on 2 things:
- The temperature of a substance
- The number of particles in a substance