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11/13

11/13. Hmwk: read text pgs. 44-48 Pg49 #9-12 DO NOW Convert 37degrees C to K 373 K to Celsius. Heat Energy and Temperature. Thermometers: Use to measure temperature How does a thermometer work? As a substance increases in temperature so does the volume (expands)

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11/13

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  1. 11/13 • Hmwk: read text pgs. 44-48 • Pg49 #9-12 DO NOW Convert • 37degrees C to K • 373 K to Celsius

  2. Heat Energy and Temperature • Thermometers: Use to measure temperature • How does a thermometer work? As a substance increases in temperature so does the volume (expands) • Why does a substance expand? Molecules are moving violently against each other

  3. Temperature: measurement of the average kinetic energy of the particles in a sample of material. Temperature is not a form of energy. ( • Two temperature scales: Celsius and Absolute K • The unit of temperature in the Celsius scale is the degree (ºC) • The unit of temperature on the Absolute scale is the Kelvin (K)

  4. Celsius Scale • Scale most commonly used in science • Freezing point of water 0 deg C • Boiling point 100 deg C • There are negative quantities

  5. Kelvin • Has the lowest possible temperature: • Absolute Zero 273.15 degrees below zero • Freezing point: 273 K • Boiling point: 373 K

  6. Convert: between absolute and Celsius temperature scales use K=ºC+273ºC=K - 273

  7. Does temperature change the volume of a substance? • Write your hypothesis. • watch temperature effects volume.htm ºC

  8. 11/17 • Hmwk: • vocabulary quiz on different forms of energy

  9. Heat and Quantity How is the quantity of heat measured? • Temperature What is the unit of heat quantity? • Calorie: quantity of heat that will increase the temperature of 1g of water by 1 deg C • Kilocalorie = 1000 calories • Any form of energy can be converted to heat

  10. Question • You have a drinking glass and a bathtub filled with room temperature water (20 deg C). Which would require more heat, the raising the temperature of the water in the glass by 80 deg C, or the bathtub to 0.5 deg C? • Glass 250mls water • Tub 400,000mls water

  11. Solution 250 mls x 80degC = • 20,000 calories of heat 400,000mls x 0.5 degC = • 200,000 calories of heat

  12. What is the measurement of released heat? • Heat is released during a chemical reaction and it’s measurement is called calorimetry. What measures the release of heat? • Calorimeter: reaction takes place in a chamber, surrounded by a known mass of water How does it work? • Heat released from the reaction raises the T of the known mass of water • T measured by thermometer

  13. Heat is transferred • Amount of heat energy required to raise the T of 1g water by 1 degC = • Specific heat of water • specific heat capacity: water = 4.18J/g • find heat absorbed (Q) by: Q=mCT m=mass T=change in temperature specific heat capacity (C) Heat_Transfer.asf

  14. Practice Problem • A 2000 g mass of water in a calorimeter has its temperature raised by 3.0 deg C while an exothermic chemical reaction is taking place. How much heat is transferred to the water by the heat of reaction?

  15. Regents Question: 06/02 #16 Which change in the temperature of a 1-gram sample of water would cause the greatest increase in the average kinetic energy of its molecules? (1) 1°C to 10°C (3) 50°C to 60°C (2) 10°C to 1°C (4) 60°C to 50°C þ

  16. LE 8-6a Reactants Amount of energy released (G < 0) Energy Free energy Products Progress of the reaction Exergonic reaction: energy released

  17. LE 8-6b Products Amount of energy required (G > 0) Free energy Energy Reactants Progress of the reaction Endergonic reaction: energy required

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