Transcript
- Slide 1
- Slide 2
- Chemistry Ms. Piela
- Slide 3
- Heat transfers in chemical reactions Energy Definition: The capacity to do work or supply heat Basic Types: Mechanical, Electrical, Potential, Kinetic
- Slide 4
- Energy that is stored within chemical bonds Determined by the arrangement and bonding of atoms Examples: Gasoline, Food, etc
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- Exothermic processes (exits) Heat flows out of a system
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- System loses heat (negative sign) Examples: Explosions!, Sun, Fire
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- Endothermic processes (enter) Heat is absorbed from surroundings
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- System gains heat (positive sign), Heat change is > 0 Examples: Boiling water, ice melting
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- Energy transfers due to temperature differences between objects Flows from hot to cold until temperature equilibrium is reached
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- Energy cannot be created or destroyed, only transferred Can be transformed Example: HeatMechanicalElectrical
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- Calorie (cal) the amount of heat needed to raise 1 gram of water 1 C Heat calorie is not to be confused with dietary calories 1 dietary Calorie = 1 kcal = 1000 cal Joule (J) metric unit of heat and energy Conversion Factor! Woo!
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- It takes 50.2 J to raise the temperature of a 100.0 g piece of glass. How many calories is this?
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- A small chocolate bar has about 210,000 calories. How many Joules is this?
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- The amount of heat required to raise 1 gram of a substance 1 C Heat capacity is the amount of heat required to raise a substance 1 C
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- q = heat (J or cal) m = mass (g) C = specific heat T = Change in Temp. ( C)
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- Specific heat plays a role in buffering climates Specific heat of land = 0.8 J/g C Specific heat of water = 4.184 J/g C How does this help buffer climates? Water heats up slower and cools down slowly, releasing heat gradually
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- On the notes, youll see a table of specific heat capacities for common metals. Well be using these throughout all the problems in this section, so keep it handy!
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- A 1.55 g piece of stainless steel absorbs 141 J of heat when its temperature increases by 178 C. What is the specific heat of stainless steel?.511 J/g C
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- How much heat is required to raise the temperature of 250.0 g of mercury from 52 C to 60 C? 280 J
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- If the initial temperature of a 10.0 g substance is 20.0 C and 100.0 J of heat are absorbed, what is the final temperature? The specific heat of the substance is 1.15 J/g C. 28.7 C