chemistry week 29 please get out your notebooks and homework!
TRANSCRIPT
Chemistry Week
29
Please get out your notebooks and
homework!
April 2, 2012
AGENDA:1 – Bell Ringer &
Agenda2 – Review HW3 – CN: Heat Curves and
Heat Capacity4 – Work Time: Heat
Curves and Heat Capacity
Today’s Goal:Students will be able to
interpret heat curves and calculate heat.
Homework1. Heat Curves and
Heat Transfer2. Binder Check!
Tuesday, April 2nd
Objective: Students will be able to interpret heat
curves and calculate heat.
Bell Ringer:If the temperature of the
surrounding decreases, is this process endothermic or exothermic. Explain using the terms heat, surrounding and system.
30 seconds Remaining…
Tuesday, April 2nd
Objective: Students will be able to interpret heat
curves and calculate heat.
Bell Ringer:If the temperature of the
surrounding decreases, is this process endothermic or exothermic. Explain using the terms heat, surrounding and system.
April 2, 2012
AGENDA:1 – Bell Ringer &
Agenda2 – Review HW3 – CN: Heat Curves and
Heat Capacity4 – Work Time: Heat
Curves and Heat Capacity
Today’s Goal:Students will be able to
interpret heat curves and calculate heat.
Homework1. Heat Curves and
Heat Capacity2. Binder Check!
Cornell Notes
Topic: Heat Curves and Heat Capacity
Date: 4/2/2013 Measuring energy:
Universe = Surroundings + System
SurroundingsSurroundings
SystemHeat Heat
Endothermic Exothermic
Review from
yesterday
q =(-)
q =(+)
q = q of the surrounding
Cornell Notes
Heat Curve = shows how temperature of the surroundings are changing during a chemical reaction.
Diagram Heat
Curves.
Exothermic
Time
Tem
pera
ture
Endothermic
TimeTem
pera
ture
Temp. of surroundin
gs will increase.
Temp. of surroundin
gs will decrease.
Cornell Notes
Heat Capacity = the heat needed to increase the temperature of an object exactly 1°C. The heat capacity of a substance
depends on both its mass and its chemical composition.
Specific Heat (CP) = specific to a particular compound; it is the amount of heat required to raise 1 gram of that compound 1°C. Units = J/g ·°C Cp = q = heat
(J)_________ m x ∆T mass (g) x change in temp (∆ T)
Describe heat
capacity.
Describe
specific heat.
Cornell Notes
How can you
calculate the heat
required to change the temperatur
e of an object?
Heat Capacity = the amount of heat required to change the temperature of an object (based upon the object’s specific heat.)
q = m · Cp · ∆T
q = heatm = mass of the substanceCp = specific heat of the
substance∆T = change in temperature of
object ∆T = Tfinal – Tinitial
Cornell Notes
Example #1
If the specific heat of water is 4.18 J/g°C, what is the heat used if 4.5 grams of water is raised from a temperature of 15°C to 75 °C.q = m · Cp · ∆T
m = 4.5 gCP = 4.18 J/g°C
∆T = 75 °C – 15 °C = 60 °C q = ( 4.5 g) (4.18 J/g°C) (60°C) q = 1128.6 J or 1.1286 kJ
q = x
Cornell Notes
Example #2
If the specific heat of water is 4.18 J/g°C, what is the mass of the water if - 4500 J of heat was used when the temperature was changed from 85°C to 20 °C.q = m · Cp · ∆T
q = - 4500 J CP = 4.18 J/g°C
∆T = 20 °C – 85 °C = - 65 °C - 4500 J= (x) (4.18 J/g°C) (- 65°C) m = 16.6 g
m = x