Presentation on theme: "What do you think? Place the 2 groups of objects below in order from coldest to hottest. Cheese, popsicle, napkin Bonfire, napkin, fried egg."— Presentation transcript:
1What do you think?Place the 2 groups of objects below in order from coldest to hottest.Cheese, popsicle, napkinBonfire, napkin, fried egg
2Is the napkin hot or cold? So…Is the napkin hot or cold?
3Temperature, Phases of Matter and Heat (Chapter Eleven)Temperature, Phases of Matter and Heat
4Back to the hot and cold … Using the words “hot” or “cold” can sometimes be confusing…or relative (some of you think the room is too cold…some don’t)To reduce confusion, an object should be described by its temperature.SUBJECTIVE vs OBJECTIVE
5TemperatureIs a measure of the kinetic energy of the particles in an object.The faster the particles move, the higher the temperatureTemperature is independent of the amount of the substance being measured (a little bit can have the same temperature as a whole bunch)
6TemperatureThere are two common temperature scales. The Celsius scale: Water freezes at 0 C Water boils at 100 C (metric) On the Fahrenheit scale: Water freezes at 32 F Water boils at 212 F. (English or standard)
7The 3rd Temperature Scale (though not so common) Kelvin (K) – SI unit – starts at absolute zeroNO degrees, labelled in “Kelvins”Fahrenheit (oF) – US unitCelsius (oC) – metric unit – broken into 100 equal units between freezing and boiling water
8Absolute zero Absolute zero is -273°C. You cannot have a temperature lower than absolute zero.Think of absolute zero as the temperature at which atoms are “frozen.”
10Thermometer A thermometer is an instrument that measures temperature Thermometers you have likely seen uses colored liquid alcohol to sense temperature- because alcohol stays liquid over a wide range of temperatures.
11How does a thermometer work? They work due to thermal expansionAs a substance gets hotter, its particles move faster. The particles do not expand, but they need to spread out…this spreading is called thermal expansion.When the thermometer is warmed, the liquid inside expands and rises up in the tube.
12Thermal Expansion Thermal Contraction object is heated up particle movement increasesparticles spread outThermal Contractionobject cools downparticle movement decreasesParticles stay closer together.
14Converting to KelvinThe Kelvin temperature scale is useful in science because it starts at absolute zero.To convert from Celsius to Kelvin, you add 273 to the temperature in Celsius
15Let’s convert... What temperature was it this morning when you got up? Let’s convert it to Celcius:
16Another temperature conversion… Look at the conversion formulas earlier in your notes.It is 77 in this room.What unit would that be in?Let’s convert that number to the other 2 units.
17What temperature really is… Temperature measures the kinetic energy per atom due to random motion. (how fast the molecules are moving)
18What temperature really is… The back-and-forth jiggling of atoms is caused by thermal energy, which is a kind of kinetic energy- (E an object possesses due to temperature)BROWNIANMOTION.Atoms are in constant motion, even in a solid object.
19More on temperature (without having to listen to me)! Watch “Brainpop” on TemperatureTake review quiz on Temp.
20Tell your neighbor!1.) Why can’t there be a temperature lower than absolute zero? 2.) Explain the scientific meaning of the word random. 3.) Which is colder, 0 ˚C or 20 ˚F ?
22What is heat? Heat is energy of the atom that is moving. Heat flows any time there is a difference in temperature.Because your hand has more thermal energy than the chocolate, thermal energy flows from your hand to the chocolate and the chocolate begins to melt.
23Soda and HeatHow does soda get cold in a cooler of ice?
24What is Thermal EnergyRemember, temperature is the measure of particle movement due to temperature )(kinetic energy)…..however, the TOTAL energy in ALL of the particles in a substance is called its thermal energy….the more particles there are, the more thermal energy it contains.
26Heat, Temperature, and Thermal Energy Heat, temperature, and thermal energy are related, but are not the same thing.The amount of thermal energy depends on the temperature but it also depends on the amount of matter you have.
28Units of heat and thermal energy The metric unit for measuring heat is the joule.This is the same joule used to measure all forms of energy, not just heat.
29How are calories related to heat? How can you determine how much “energy” is contained in a substance?Use a calorimeter. It uses the amount of heat generated by burning something as a measure of how much energy it contains.
30Heat and thermal energy Thermal energy is often measured in calories.One calorie is the amount of energy it takes to raise the temperature of one milliliter of water by one degree Celsius.
31How a calorimeter works: Food to be tested is burned below a container of water.The temperature increase in the water is measured.A calorie is the amount of energy needed to change the temp 1 gram of water by 1oC.
32Heat Transfer There are three ways that heat is transferred: Thermal ConductionConvectionThermal Radiation
33Thermal ConductionHeat conduction is the transfer of heat by the direct contact of particles of matter.Conduction occurs between two materials at different temperatures when they are touching each other.Where is the heat energy conducted to and from in this system?
35Thermal conductors and insulators Materials that conduct heat easily are called thermal conductors and those that conduct heat poorly are called thermal insulators.Is a down coat a conductor or an insulator?
37Substances that transfer heat easily are called conductors The best conductors are metals.
38Substances that do not conduct thermal energy very well are called insulators.
39ApplicationFor years, the plumbing in homes was done in copper piping. Now they are done in PVC. What are some reasons that this change occurred?
40ConvectionConvection is the transfer of heat through the motion of matter such as air and water.In a container, warmer fluid rises to the top and cooler fluid sinks to the bottom.This is called natural convection.
42ConvectionConvection is mainly what distributes heat throughout a room.
43RadiationTransfer of heat through electromagnetic waves across empty space.
44Thermal radiationHeat from the Sun is transferred to Earth by thermal radiation.The higher the temperature of an object, the more thermal radiation it emits.All the energy the Earth receives from the Sun comes from thermal radiation.
45Thermal radiation Thermal radiation is also absorbed by objects. The amount of thermal radiation absorbed depends on the surface of a material.Dark surfaces absorb most of the thermal radiation they receive.Silver or mirrored surfaces reflect thermal radiation
46EquilibriumThermal equilibrium occurs when two bodies have the same temperature.No heat flows in thermal equilibrium because the temperature is the same in the two materials.
47I remember that!1.) What are the three ways heat is transferred? 2.) Heat from the Sun is transferred by _______ _________. 3.) When heat is transferred by two objects touching, it is called _____________.
50The Phases of MatterIntermolecular forces tend to bring molecules together. Intermolecular forces have to be overcome in order to change phase.
51Sing it Baby…. http://www.youtube.com/watch?v=btGu9FWSPtc
52Solid A solid holds its shape and does not flow. The molecules in a solid vibrate in place, but on average, don’t move far from their places
53LiquidA liquid holds its volume, but does not hold its shape—it flows.Liquids flow because the molecules can move around.
54GasA gas flows like a liquid, but can also expand or contract to fill a container.A gas does not hold its volume.The molecules in a gas have enough energy to completely break away from each other.
55PlasmaAt temperatures greater than 10,000˚C, the atoms start to come apart and become a plasma.Atoms are broken apart into separate positive ions and negative electronsConducts electricity and is formed in lightening and inside stars.
56I remember that!1.) What are the three phases of matter? 2.) Liquid holds its volume, but does not hold its ___________ . 3.) The melting point and the freezing point for water is ___ degrees Celsius.
58Phases of Matter and Phase Change Boiling pointMelting pointFreezing pointVaporization/evaporationCondensationPhase Change Diagram
59Boiling PointThe temperature at which a liquid becomes a gas is called the boiling point.
60Vaporizaton and Evaporation Also known as the boiling pointWhen liquid turns to vapor (gas)
61Melting PointThe melting point is the temperature at which a substance changes from a solid to a liquid.
62Freezing PointThe freezing point is the temperature at which a substance changes from a liquid to a solid.
63CondensationCondensation is the point at which a substance changes from a gas to a liquid.
64Melting and boiling points of common substances Materials have a wide range of melting and boiling points.
65So what?So what really is the difference between the boiling point and the condensation point of a substance?So what really is the difference between the freezing point and the melting point of a substance?
68DO NOW: Quick Quiz – True/False Heat is the transfer of energy between two objects with different temperatures.Conduction occurs in fluids.Convection currents result from temperature differences in gases and liquids.Radiation is the means by which the energy from the sun is transferred to Earth.