Chemistry Week 29 Please get out your notebooks and homework!

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