
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?
http://ca.pbslearningmedia.org/resour
ce/nvsn6.sci.bio.fuel/food-is-fuel/
 define
the terms system and surroundings in the
context of a chemical reaction.
 identify the system and surroundings in a
thermochemical reaction.
 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 thermochemical rtn
 Apply Hess’s law of heat summation in a
thermochemical equation.
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.
 COMPARE
AND CONTRAST USING VENN DIAGRAM
 Exothermic Process:
o
o
o
Heat is release to the surroundings (surroundings warms
up)
The system loses heat (system products cools down)
q= negative
 Endothermic
o
o
o
Process:
Heat is absorbed from the surroundings (surroundings
cool down)
The system gains heat (system products warms up)
q= positive
 Calorie
(cal) : quantity of heat needed to raise
the temperature of 1g of pure water to 10C.
o
o
1 Calorie = 1 Kilocalorie = 1000 calories
20 Cal (dietary potential energy) = 20 Kcal (when energy
completely used up/released)
 Joules
o
o
o
o
(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: amount of heat needed to increase
the temperature of an object to exactly 10C.
( Unit for heat capacity = J/0C)
 Heat
o
o
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
 Thumbs
Up
 Thumbs Down
 Thumbs side
 What
is your level of understanding on:
System and surroundings
o Endothermic and Exothermic
o Calorie/Kilocalorie
o Heat Capacity
o Specific Heat Capacity
o
•
•
•
Formula for calculating Specific Heat
Unit for Specific Heat
Specific Heats of some common substances
(see PHC: table 17.1, page 508)
 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?