Think-pair-share

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# Think-pair-share - PowerPoint PPT Presentation

Think-pair-share. Respond to at least One question below using the organizer provided. Be prepared to share your thoughts QUESTIONS: 1. Describe what happens to a rat that has been eaten by a python. 2. What is the function of the digestive system? What are calories?

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Presentation Transcript
Think-pair-share
• Respond to at least One question below using the organizer provided. Be prepared to share your thoughts
• QUESTIONS:
• 1. Describe what happens to a rat that has been eaten by a python.
• 2. What is the function of the digestive system? What are calories?
• 3.How can you measure the calories contained in food?
• 4. What do you think happens if a person eats more calories than their body needs?

### THERMOCHEMISTRY

http://ca.pbslearningmedia.org/resource/nvsn6.sci.bio.fuel/food-is-fuel/

SWBAT…..
• define the terms system and surroundings in the context of a chemical reaction.
• identify the system and surroundings in a thermochemicalreaction.
• describe how heat is transferred in endothermic and exothermic reactions
• Calculate specific heat of a substance in calories and joules
• Calculate enthalpy changes in a thermochemicalrtn
• Apply Hess’s law of heat summation in a thermochemical equation.
Heat and Work:
• TERMINOLOGIES:
• Thermochemistry: studies energy changes in chemical reactions and changes of state.
• Heat (q): is the transfer of energy from one object to another because of temperature difference (warmer to cooler object)
• System: part of the universe being studied or focus of attention (e.g. reactants and products of a reaction)
• Surroundings: the immediate vicinity of the system (e.g. container, space, universe, e.t.c.)
• Law of conservation of energy: states that energy is neither created nor destroyed in any chemical or physical process.
Exothermic and EndothermicProcesses
• COMPARE AND CONTRAST USING VENN DIAGRAM
• Exothermic Process:
• Heat is release to the surroundings (surroundings warms up)
• The system loses heat (system products cools down)
• q= negative
• Endothermic Process:
• Heat is absorbed from the surroundings (surroundings cool down)
• The system gains heat (system products warms up)
• q= positive
Unit for Measuring Heat Flow
• Calorie (cal) : quantity of heat needed to raise the temperature of 1g of pure water to 10C.
• 1 Calorie = 1 Kilocalorie = 1000 calories
• 20 Cal (dietary potential energy) = 20 Kcal (when energy completely used up/released)
• Joules (S.I. Unit of energy)
• One Joule (1J) of heat is the energy needed to raise the temperature of 1g of pure water to 0.23900C
• Unit Conversion:
• 1J = 0.2390 cal 4.184J = 1cal
• 1000J = 1kJ (kiloJoules)
Heat Capacity
• Heat Capacity: amount of heat needed to increase the temperature of an object to exactly 10C. ( Unit for heat capacity = J/0C)
• Heat capacity depends on:
• Mass of an object
• Chemical composition of the object
• Specific Heat Capacity (C): is the amount of heat it takes to raise the temperature of 1g of substance (object) to 10C. (Unit for Specific Heat = J/(g.0C) or J/(kg.0C) or kcal/(kg.0C) ). Remember: 1000g = 1Kg
Check for understanding
• Thumbs Up
• Thumbs Down
• Thumbs side
• What is your level of understanding on:
• System and surroundings
• Endothermic and Exothermic
• Calorie/Kilocalorie
• Heat Capacity
• Specific Heat Capacity
Calculating Specific Heat/Capacity(C) of a Substance
• Formula for calculating Specific Heat
• Unit for Specific Heat
• Specific Heats of some common substances (see PHC: table 17.1, page 508)
Heat Math problems
• When 435J of heat is added to 3.4g of olive oil at 210C, the temperature increases to 850C. What is the specific heat of the olive oil?
• How much heat is required to raise the temperature of 250.0g of mercury 520C?
• An orange contains 445kJ of energy. What mass of water could the same amount of energy raise from 25.00C to the boiling point?