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Agenda 4/16/2014
• Slip quiz 5 Aday
• Calorimetry Lab
• Note: Ch 15 Test – Next Tuesday, April 22
Objectives: 1. Find the amount of heat released by a potato
chip.
2. Solve problems involving heat flow and temperature
changes.
5 Aday - Slip quiz
1. State the Law of Conservation of
Energy.
2. What is energy?
5 Aday - Slip quiz
1. State the Law of Conservation of
Energy.
The Law of Conservation of Energy states
that in any chemical reaction or physical
process, energy can be converted from
one form to another, but it is neither
created nor destroyed. (First Law of
Thermodynamics).
5 Aday - Slip quiz
2. What is energy?
Energy is the ability to do work or produce
heat.
Kinetic energy – energy of motion
5 Aday - Slip quiz
2. What is energy?
Energy is the ability to do work or produce
heat.
Kinetic energy – energy of motion
Potential energy – due to position of an
object
5 Aday - Slip quiz
2. What is energy?
Energy is the ability to do work or produce
heat.
Kinetic energy – energy of motion
Potential energy – due to position of an
object
chemical potential energy – energy
stored in a substance because of its
composition – chemical bonds holding
atoms together
Combustion (exothermic reaction)
Heat released when a substance burns in
oxygen Related to the energy (chemical
potential energy) stored in the bonds of the
substance
Heat (q) energy in the process of flowing
from a warmer object to a cooler object
Temperature rises when cooler object
absorbs heat (warmer object’s temperature
decreases)
Measuring Heat
Measuring temperature changes – clues to
heat flow
The SI unit of heat and energy is the joule
(J)
Amount of heat required to raise the
temperature of one gram of pure water by
one degree Celsius is 4.184 joules (or 1
calorie).
Latin Calor = heat, warmth
Energy Units
1 Joule = 1 J
1kilo joule = 1kJ = 1000 J
1 calorie = 1 cal = 4.184J
1 kilocalorie = 1kcal = 1000cal
1 nutritional Calorie
1 Calorie = 1 kcal
ChemLab16: Calorimetry
Calorimetry – heat measuring (metry)
– Safety precautions?
ChemLab16: Calorimetry
Calorimetry – heat measuring (metry)
2. Safety precautions?
–Tie back hair, no dangling earphones/jewelry/
loose fitting clothing
–goggles
–No eating the samples!
ChemLab16: Calorimetry
Calorimetry – heat measuring (metry)
3. Hypothesis about how the quantity of heat
produced by the combustion reaction (of a potato
chip) will compare to the quantity of heat
absorbed by the water.
ChemLab16: Calorimetry
Calorimetry – heat measuring (metry)
3. Hypothesis about how the quantity of heat
produced by the combustion reaction (of a potato
chip) will compare to the quantity of heat
absorbed by the water.
–The heat produced by the reaction will be more
than the heat actually absorbed by the water
because some of the heat produced will escape
into the surroundings and not be absorbed by the
water.
ChemLab16: Calorimetry
4. Formula for calculating the quantity of heat
absorbed by the water
q = c x m x ΔT
Where q is heat absorbed (by water)
c is the specific heat (of water)
m is the mass (of the water)
ΔT is the change in temperature (of the water)
ChemLab16: Calorimetry
4. formula for calculating the quantity of heat
absorbed by the water
q = c x m x ΔT
Specific heat of any substance is the heat
required to raise the temperature of 1g of the
substance by 1 degree Celsius.
Different substances have different specific heats.
Specific heat for water is 4.184 J/g°C
ChemLab16: Calorimetry
5. Assuming the potato chip contains compounds
made up of carbon and hydrogen (organic
compounds) what gases will be produced in the
combustion reaction?
ChemLab16: Calorimetry
5. Assuming the potato chip contains compounds
made up of carbon and hydrogen (organic
compounds) what gases will be produced in the
combustion reaction?
CH4 + 2 O2

CO2(g) + 2 H2O(g)
ChemLab16: Calorimetry
Procedure
– Re-written in own words.
–Any questions? 9 stations – set up (check)
–Use data collection unit and fast response
temperature probe – get the wire arranged so it
will not get close to the flame of the burning
potato chip ahead of time.
–Let the burned chip cool.
ChemLab16: Calorimetry
Data Table (Results)
Mass of beaker and 50mL of water
Mass of empty beaker
Mass of water in beaker
Mass of potato chip
Highest temperature of water
Initial temperature of water
Change in temperature
ChemLab16: Calorimetry
Analyze and Conclude
Answer all questions using complete sentences
that incorporate the question into the answer you
write.
Example:
1. The burning of a potato chip is an exothermic
reaction. I know this because I saw a bright
flame (light energy) and there was heat given
off by the reaction which we used to heat
water.
1 nutritional Calorie
1 Calorie = 1 kcal
1 kilocalorie = 1kcal = 1000cal
1 calorie = 1 cal = 4.184J
Homework
Read Section 16.1 Energy
Answer questions 7 – 11 in Section 16.1
Assessment (p. 495)
Read Section 16.2 Heat in Chemical Reactions
and Processes
Describe and sketch a calorimeter and explain how it can
be used to measure the amount of heat absorbed or
released during a chemical or physical process.
Copy the 2 diagrams at the top of page 500 (Figure 16-8)
including the caption.
Copy table 16-4
Explain the meaning of ΔHrxn. Why is ΔHrxn sometimes
positive and sometimes negative.