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Unit 2, lesson 2 Temperature

Unit 2, lesson 2 Temperature. Kinetic Theory of Matter. All matter is made up of tiny particles that are always moving, even if the matter that they make up is not. All particles of matter have kinetic energy The faster particles move, the more kinetic energy they have.

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Unit 2, lesson 2 Temperature

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  1. Unit 2, lesson 2Temperature

  2. Kinetic Theory of Matter • All matter is made up of tiny particles that are always moving, even if the matter that they make up is not. • All particles of matter have kinetic energy • The faster particles move, the more kinetic energy they have. • The kinetic theory of matter states that all of the particles that make up matter are constantly in motion.

  3. Kinetic Theory of Matter, cont… • The motion of these particles is random. • The individual particles have different amounts of kinetic energy, but their average kinetic energy takes into account their different random motions. • Solids, liquids, and gases have different average kinetic energies.

  4. The particles in a liquid move much more freely than the particles in a solid. They slide past and tumble over each other. The particles in a solid do not move around very much. The particles in a gas are far apart, move at high speeds, and collide with one another.

  5. How does temperature relate to kinetic energy? • Temperatureis a measure of the average kinetic energy of all the particles in an object. • The warmer a substance is, the faster its particles move.

  6. Temperature cont. • Hot cocoa has a higher temperature than cold chocolate milk. • Since the cocoa’s particles are moving faster, these particles have greater average kinetic energy. • In the cold milk, the particles are moving slower, which means these particles have less average kinetic energy.

  7. Measuring Temperature • A thermometer is used to measure temperature. • Thermometers usually consist of a liquid, such as mercury or alcohol, sealed inside a narrow glass tube. • When the tube is heated, the particles of the liquid speed up and spread out so the particles take up more space or volume and you see the level of the liquid move up the tube. • When the tube is cooled, the particles of the liquid slow down and move closer, taking up less volume and the liquid moves down the tube.

  8. As the temperature of the liquid decreases, volume decreases. As the temperature of the liquid increases, volume increases.

  9. Measuring Temperature cont. • A thermometer has a scale of numbers and units. • When you read a thermometer scale, you read the temperature (the average kinetic energy of particles) of the matter that surrounds it. • Thermometers can have different scales, and the temperature you see depends on which scale is used.

  10. Temperature Scales • The three common scales for measuring temperature are Fahrenheit, Celsius, and Kelvin. • In the Celsius and Fahrenheit scales, temperature is measured in units called degrees. • Degrees(°) are equally spaced units between two points. The space between degrees can vary from one scale to another. • In the Kelvin scale, no degree sign is used. The unit is just called a Kelvin.

  11. Temperature Scales cont. • In the U.S., the Fahrenheit scaleis the most common temperature scale. • This scale is divided into degrees Fahrenheit (°F). • On this scale, water freezes at 32°F and boils at 212°F. • The temperature scale used in most of the world is the Celsius scale. • The Celsius scale is divided into degrees Celsius (°C), which are larger units than °F. • On this scale, water freezes at 0°C and boils at 100°C

  12. Temperature Scales cont. • The temperature scale commonly used in physics is the Kelvin scale. • Units on this scale are called Kelvins (K) and are the same size as °C. • On the Kelvin scale, water freezes at 273 K and boils at 373K. • Experiments have led scientists to conclude that -273°C is the lowest temperature possible. • No more thermal energy can be removed from matter at this temperature. • Zero on the Kelvin scale represents -273°C and is called absolute zero.

  13. Converting Temperature Scales • Fahrenheit and Celsius scales can be converted to the other by using certain equations: • To convert ᵒF to ᵒC, you take the temperature in ᵒF subtract 32, multiply by 5 and then divide by 9 to find ᵒC. • Example: 85ᵒF = • 85 – 32 = • 53 x 5 = • 265 / 9 = 29ᵒC 53 265 29.4

  14. Converting Temperature Scales, cont… • To convert ᵒC to ᵒF, you take the temperature in ᵒC, multiply by 9, divide by 5 and then add 32 to find ᵒF. • Example: 76ᵒC = • 76 x 9 = • 684 / 5 = • 136.8 + 32 = 169ᵒF 684 136.8 168.8

  15. Converting Temperature Scales, cont… • To convert K to ᵒC, you take the temperature in K and simply subtract 273.15 and your answer will be ᵒC. • Example: 0 K = • 0 – 273.15 = -273ᵒC -273.15

  16. Converting Temperature Scales, cont… • To convert K to ᵒF, you take the temperature in K, subtract 273.15, multiply by 1.8, and then add 32 to find ᵒF. • Example: 100 K = • 100 – 273.15 = • -173.15 x 1.8 = • -311.67 + 32 = -280ᵒF -173.15 -311.67 -279.67 or -280

  17. Unit 2 Lesson 3 Thermal Energy and Heat

  18. Unit 2Lesson 3 Thermal Energy and Heat Thermal, Under Where? What is thermal energy? • Thermal energyis the total kinetic energy of all particles in a substance. • Thermal energy is measured in joules (J).

  19. Unit 2Lesson 3 Thermal Energy and Heat What is the difference between thermal energy and temperature? • Temperature is the average kinetic energy of particles. • Thermal energy is the total kinetic energy of all the particles. • Even though two materials might have the same temperature, their thermal energies might be different because thermal energy depends on how many particles are present in the object. • For example, a glass of water can have the same temperature as a lake, but the lake has much more thermal energy because the lake contains many more water molecules.

  20. Unit 2Lesson 3 Thermal Energy and Heat Heat It Up! What is heat? • Heat is the energy transferred from an object at a higher temperature to an object at a lower temperature. • Energy in the form of heat always flows from warmer to colder.

  21. Unit 2Lesson 3 Thermal Energy and Heat How is heat related to thermal energy? • Adding or removing heat from a substance will affect its temperature and thermal energy. • Heat, however, is not the same as thermal energy and temperature. • Thermal energy and temperature are properties of a substance. Heat is the energy involved when these properties change.

  22. Unit 2Lesson 3 Thermal Energy and Heat How is heat measured? • Heat is measured in two ways. • One way is the calorie (cal). • One calorie is equal to the amount of energy needed to raise the temperature of 1 g of water by 1⁰C.

  23. Unit 2Lesson 3 Thermal Energy and Heat How is heat measured? • Heat is also measured in joules (J) because heat is a form of energy. • One calorie is equal to 4.18 joules.

  24. Unit 2Lesson 3 Thermal Energy and Heat How is heat measured? • In nutrition, 1 Calorie (with a capital C) is actually 1 kilocalorie, or 1,000 calories. • To find out how many calories are in food, a sample of food is burned inside an instrument called a calorimeter. • The change in temperature in the calorimeter is used to calculate how much energy is released from the food sample.

  25. Unit 2Lesson 3 Thermal Energy and Heat How can heat affect the state of an object? • The state of a substance depends on the speed of its particles. • Adding energy in the form of heat to a substance can result in a change of state. • Removing energy in the form of heat from a substance can also result in a change of state.

  26. Unit 2Lesson 3 Thermal Energy and Heat Keep Your Cool What is conduction? • Heat energy can be transferred in three main ways: conduction, convection, and radiation. • Conduction is the transfer of energy as heat from one substance to another through direct contact. • As long as two objects are in contact, conduction continues until the temperatures of the objects are equal.

  27. Unit 2Lesson 3 Thermal Energy and Heat What is conduction? • A conductoris a material that transfers heat very well. • Metals are typically good conductors. • An insulator is a material that is a poor conductor of heat. • Wood, paper, and plastic foam are examples of good insulators.

  28. Unit 2Lesson 3 Thermal Energy and Heat What is convection? • Convectionis the transfer of energy as heat by the movement of a fluid like a liquid or gas. • Convection occurs when a cooler, denser mass of gas or liquid replaces a warmer, less dense mass of gas or liquid by pushing it upward.

  29. Unit 2Lesson 3 Thermal Energy and Heat What is convection? • When water is boiled, the water moves in roughly circular patterns because of convection. • This motion is due to density differences that result from temperature differences. • The motion is called a convection current. Convection currents are found in all fluids, liquids and gases.

  30. Unit 2Lesson 3 Thermal Energy and Heat What is radiation? • Radiation is the transfer of energy by electromagnetic waves. • All objects, including the sun and all living things, emit radiation. • When radiation is emitted from one object and is absorbed by another, the result is often a transfer of heat. • Radiation can travel through empty space.

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