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Warm Up

Warm Up. Rank liquids, solids, and gasses in order of increasing kinetic energy. What state(s) of mater have a definite volume? What state(s) of matter have a definite shape? What is one property that both solids and liquids share?. Warm-up.

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Warm Up

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  1. Warm Up • Rank liquids, solids, and gasses in order of increasing kinetic energy. • What state(s) of mater have a definite volume? • What state(s) of matter have a definite shape? • What is one property that both solids and liquids share?

  2. Warm-up • What is the final temperature of a 50.0 g piece of glass if it absorbs 5275 joules of heat and its specific heat capacity is 0.50 J/g°C? The initial temperature of the glass is 20.0°C. • K-Money (K$)

  3. Energy of Phase Changes Unit 8, Day 2 Kimrey 27 November 2012

  4. When a substance changes temperature. • Specific Heat = The amount of energy required to raise the temperature of 1 gram of a substance by 1°C. • Note! Every substance has a unique specific heat. • q=mcΔT

  5. q=mcΔT • q = heat absorbed or released (most often in Joules) • m = mass of the sample in grams • c = the specific heat of the substance (J/g°C) • ΔT = the change in temperature in degrees Celsius • When solving a word problem, start by writing down your givens and figuring out what you are looking for. Then solve for the variable.

  6. Example • How many joules of heat are needed to raise the temperature of 10.0 g of aluminum from 22°C to 55°C, if the specific heat of aluminum is 0.90 J/g°C?

  7. Example • Calculate the heat capacity of a piece of wood if 1500.0 g of the wood absorbs 6.75×104 joules of heat, and its temperature changes from 32°C to 57°C

  8. Example • To what temperature will a 50.0 g piece of glass raise if it absorbs 5275 joules of heat and its specific heat capacity is 0.50 J/g°C? The initial temperature of the glass is 20.0°C.

  9. What happens when a substance changes phases. • Heat of fusion- energy required to melt a substance. 334 J/g for water • q= m Hf • Heat of vaporization- energy required to vaporize a substance. 2260 J/g for water • q= m Hv

  10. Example • How much energy is required to melt 15.0 grams of water?

  11. Example • How much energy is required to vaporize 25.0 grams of water?

  12. Example • How much energy is required to melt 255.0 grams of water?

  13. What happens when you heat an ice cube until it all vaporizes? • Remember when you heat a substance one of two things happens: • The substance changes temperature • The substance changes state of matter • This means we need to calculate the energy involved in each step then add it all up.

  14. Example • Calculate the energy needed to turn 50 grams of liquid water with a temperature of 56°C to water vapor with a temperature of 150°C.

  15. Example • An ice cube with a mass of 15 grams and an initial temperature of -10°C is heated until all 15 grams of water is a vapor with a temperature of 105°C. Calculate the energy needed to do this.

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