1 / 42

What is heat?

What is heat?. Heat is a form of:. E N E R GY ! ! !. What has heat?. Everything in the universe has heat energy! Your BODY , your CAR …even ICE !. If Heat is a form of energy, then what is temperature?. Temperature: Temperature is ONLY a measurement of particle motion .

rainer
Télécharger la présentation

What is heat?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. What is heat? Heat is a form of: E N E R GY ! ! !

  2. What has heat? Everything in the universe has heat energy! Your BODY, your CAR…even ICE!

  3. If Heat is a form of energy, then what is temperature? Temperature: • Temperature is ONLY a measurement of particle motion. • Temperature measures the average kinetic energy of the molecules of an object or substance.

  4. Heat versus temperature SUMMARY: HEAT IS ENERGY TEMPERATURE IS A MEASUREMENT OF MOTION

  5. There are 3 main scales used to measure temperature 3 Main Temperature Scales Celsius Fahrenheit Kelvin

  6. TEMPERATURE SCALES

  7. Fahrenheit What you need to know about the Fahrenheit Temperature Scale • 1) Fresh water freezes at 32 degrees Fahrenheit • 2) Fresh water boils at 212 degrees Fahrenheit

  8. Celsius What you need to know about the Celsius Temperature Scale • 1) Fresh water freezes at 0 degrees Celsius • 2) Fresh water boils at 100 degrees Celsius • 3) It is the most commonly used scale except for in the United States.

  9. Kelvin What you need to know about the Kelvin Temperature Scale • 1) There are NO NEGATIVE NUMBERS • 2) Based on absolute zero (all molecule movement has stopped). • 3) The size of a Kelvin degree is equal in magnitude (size) to a Celsius degree.

  10. How do we measure temperature? Temperature is measured with thermometers. There are several types of thermometers.

  11. Types of Thermometers THERMOMETER TYPES: • Liquid Thermometer • Bimetallic strip • Digital

  12. Liquid Thermometer Liquid Thermometer • Can only measure temperatures in a certain range. • Uses the expansion of liquid alcohol or mercury (Hg) to indicate changes in temperature.

  13. Bimetallic Strip Bimetallic Strip • A coil is made using two different metal strips pressed together • Both strips expand and contract at different rates as the temperature changes • As the temperature changes, the coil winds and unwinds

  14. Digital Thermometers DIGITAL THERMOMETERS • Measures temperature by noting the change in current • Changes in temperature also cause electric current to change in a circuit

  15. Heat movement Heat moves from objects with higher energy to objects with lower energy

  16. Heat movement HEAT CAN MOVE IN 3 WAYS CONDUCTION CONVECTION RADIATION

  17. CONDUCTION For heat to be transferred by conduction: • objects must be in direct contact with each other— • THEY MUST BE TOUCHING!!!

  18. CONVECTION Convection: • Transfer of energy by the movement of fluids with different temperatures • For it to be fluid, it can be a liquid or a gas!

  19. RADIATION Radiation: • Transfer of energy by electromagnetic waves • NO DIRECT CONTACT!!! • Does not require a medium to travel! • It is the only way solar heat energy can travel to Earth!

  20. Conductors and Insulators Some objects act as conductors and some act as insulators. A conductor is a material that transfers heatquickly An insulator is a material that slows the transfer of heat

  21. Specific Heat Specific Heat • Describes how much energy is required to raise an object’s temperature. • The specific heat value is how much energy is required to raise 1 kg. of a substance by 1 degree Kelvin or Celsius • Denoted by “c” in calculations.

  22. Specific Heat Specific Heat Equation Energy = (specific heat) x (mass) x (temperature change) OR energy = cm t

  23. Specific Heat

  24. Kinetic Theory of Matter The Kinetic Theory of Matter explains the behavior of molecules in matter. It states that all matter is made of constantly moving particles that collide without losing energy.

  25. Thermal Expansion When the temperature of a substance is increased, its molecules move faster and usually move farther apart. This is thermal expansion. It occurs in all forms of matter (there are a few exceptions). Water is an exception – it expands when it is cooling from 4 degrees C to 0 degrees C.

  26. States of Matter There are four states of matter: Solid State Liquid State Gas State Plasma State

  27. States of Matter For Solids: • Particles are packed closely together and are constantly vibrating in place • Solids have a fixed volume • Solids have a fixed shape

  28. States of Matter For Liquids • The attractive forces between particles are weaker than in a solid • Particles can slide past each other • Liquids have a fixed volume. • Liquids do not have a fixed shape.

  29. States of Matter For Gases • Particles are farther apart than in a liquid or solid. • Attractive forces are weak. • Gases have no definite shape. • Gases have no definite volume.

  30. States of Matter For Plasma • Most common state of matter in the universe • Consists of positively and negatively charged particles. • No definite shape • No definite volume

  31. States of Matter Changes in the thermal energy of a material can cause it to change from one state to another.

  32. States of Matter Melting – When thermal energy is added to a solid, the change of a substance from a solid to a liquid is called melting. Heat of fusion – The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point, or when a liquid becomes a solid.

  33. States of Matter Freezing – Phase change of an object from the liquid phase to the solid phase. Vaporization – Change of a liquid into a gas. Evaporation-Vaporization that occurs at the surface of a liquid. Boiling – Vaporization occurring throughout the liquid.

  34. States of Matter Condensation – When a gas changes into a liquid.

  35. Heating Systems To raise indoor air temperature on a cold day, energy must be transferred into a room’s air by a heating system. Heating system – Any device or process that transfers energy to a substance to raise the temperature of the substance.

  36. Heating Systems Types of Heating Systems: • Forced Air Systems • Radiator Systems • Electric Heating Systems

  37. Thermodynamics Heating and Work increase thermal energy • You can warm your hands by either placing them near a heat source or rubbing them together • In this example, your hands would be considered to be a system. • A system can be a group of objects you can draw a boundary around to consider certain values about a scenario.

  38. Thermodynamics THERE ARE 2 TYPES OF SYSTEMS: • OPEN-Thermal energy can flow across your “boundary” or if work is done across the boundary • CLOSED – Thermal energy is contained within the “boundary” and no outside work is done.

  39. Laws of Thermodynamics First Law of Thermodynamics The increase in the thermal energy of a system equals the work done on the system plus the thermal energy transferred to the system

  40. Laws of Thermodynamics Second Law of Thermodynamics Energy moves from warmer objects (higher energy) to cooler objects (lower energy)

  41. Cooling Systems Cooling System – A device that transfers energy as heat out of an object to lower its temperature. Cooling Systems use evaporation to transfer energy from their surroundings using a refrigerant Refrigerant – A substance used in cooling systems that transfers large amounts of energy as it changes state

  42. Cooling Systems

More Related