Ch. 10 & 11 ppt.pptx

Bell work

Thursday, January 17

th

Draw the following table on the back of WS1 and fill in the boxes that you already know.

Properties Solid Liquid Gas

Amount of movement of particles

Amount of heat in particles

Test have been graded- if you did not take the

test yesterday please step outside.

• _{If you made below a 75 you are eligible for a retest.}

• _{You should come in for help and look at your test before}

you attempt the retest.

• _{It is your responsibility to schedule the retest and a time to}

look at your test

• _{Since I will not be here tomorrow you have until}

Wednesday afternoon to take the retest.

• _{You must let me know when you are taking the retest,}

You can not just show up and take it.

• _{Available times for retesting: before school, after school,}

CHEMISTRY

11.1 Thermochemistry

•

Thermochemistry

is concerned with

the heat changes

that occur during

chemical

•

Energy - the capacity for doing work

or supplying heat.

-

Energy comes in many forms.

-Kinetic Energy: the motion of

particles

-

Potential Energy: stored energy

Example

When gasoline burns, the

Question

•

A student is heating water to cook

pasta. She notices it begins to boil at

100°C. What is the temperature of the

water if she keeps boiling it for 15

Question

•

Write potential or kinetic beside

each of the following.

•

A stretched rubber band ___________

•

A cookie

___________

Heat (q) - energy that is transferred

from one object to another because of a

temperature difference between them.

Heat always flows from a warmer object

to a cooler

object. Heat

cannot be

In chemistry, we take the

system’s

point of view.

*The system is the part of

the universe on which

you focus your attention.

*The surroundings are

everything else in the

In any chemical or physical process,

energy is neither created nor destroyed

.

Ex. Heat may be lost by the system,

but it is not destroyed. It is transferred

to the surroundings.

Endothermic process -

system absorbs heat

from the surroundings.

Energy units:

calorie (cal) and joule (J)

calorie

- quantity of heat needed to

raise the temperature of one gram of

water 1

C.

*A food Calorie is used in nutrition and is capitalized. 1 Calorie = 1000 cal = 1 kcal

Ex. If a label on a candy bar indicates it contains 180 Calories, that is really 180 kcal, or 180,000 calories! If "burned", the sugar and fat in the candy bar release 180,000 cal of energy.

These are capital Calories, so a

Heat capacity- amount of heat

needed to raise the

temperature of an object 1

C.

It depends on mass and

composition.

Ex. It takes more heat to increase

the temperature of a large pot of

water than a small cup of water.

It takes more heat to raise the

Question

•

What has a higher heat capacity,

Bellwork

Friday, January 18

Write “A” if the change is endothermic

and “B” if the change is exothermic.

Melting wax

Boiling ethanol

Burning paper

Specific Heat Capacity(C)-

The amount of heat it takes to raise the

temperature of 1 g of a substance 1

C.

It can be calculated:

specific heat units = cal/g

C

or J/g

C

A low specific heat is matter

that loses or gains heat quickly

(like the tiles on the space

shuttle)

A high specific heat is matter

that loses or gains heat slowly

(like water)

Water has a uniquely high

To calculate the heat energy required for a temperature change, use the following formula: q = (m)(C)(DT)

q = heat energy either absorbed or released (J or cal)

m = mass (g)

C = specific heat of the object (cal/go_{C or J/g}o_C)

DT= change in temperature of object (o_C)

Ex. How much energy is required to heat an

iron nail with a

mass of 7.0 g

from 25

C until it

becomes red hot at 750

C?

q =

m

C

D

T

C

= 0.46J/g

C

D

T = 750-25 = 725

C

q = 7.0g(0.46J/g

C) 725

C

Ex. If 5750 J of energy are added to a 455

g piece of glass at 24.0

C, what is the

final temperature of the glass?

q = mC

D

T

C

= 0.50J/g

C

D

T = ?

5750J = 455g(0.50J/g

C)

D

T

D

T = 25

C

Ex. A 30.0 g sample of an unknown metal is

heated from 22.0

C to 59.2

C. During the

process, 1.00 kJ of energy is absorbed by the

metal. What is the specific heat of the metal?

C = q/(m

D

T)

D

T = 59.2-22.0 = 37.2

o

C

C = 1000J/ (30.0g)(37.2

o

C)

Ex. If it takes 3590 calories to heat up a

sample of water by 12.2

C, what is the mass of

the water?

q = mC

D

T

3590 cal=m(1.00cal/g

o

C)12.2

o

C

Tuesday, January 22

Work on the back of WS #3

Write the entire question!

• _{How much energy is required to heat a penny with a mass}

of 1.23 g from 15oC until it becomes red hot at 256oC? (The specific heat of cop1per is 0.385 J/g°C)

If you were absent for the molar volume of a gas lab please come talk

to me.

1) Knowns and Unknowns (variable and unit) Ex: q = ____ J

2) Formula ex: q=mCΔT 3) Rearranged formula if needed

solve for m… m=q/CΔT

4) Numbers plugged into formula, include units

5) Solved answer, include unit and proper significant figures

Be sure to include: Pick up graded

Calorimetry is the measurement of heat change for chemical and physical processes.

heat released by system = heat absorbed by surroundings

Ex. A 25 g sample of a metal at 75.0

C is placed in a

calorimeter containing 25 g of H

O at 20.0

C. The

temperature stopped changing at 29.4

C. What is the

specific heat of the metal?

q = mC

D

T

D

T

= 29.4-23.0 = 6.4

C

D

T

= 75.0-29.4 = 45.6

C

q

= 45g(4.18J/g

C)6.4

C = 1204J

q

=

q

Enthalpy (H)-

the amount of heat in

a system at a given

temperature

Enthalpy change:

Exothermic reactions have -

D

H

CH

(g) + 2O

(g)



CO

(g) + 2H

O(g) + 890 kJ

D

H = -890 kJ (energy is released)

exothermic

2H

O + 241.8 kJ



2H

(g) + O

(g)

D

H = +241.8 kJ (energy is required)

endothermic

Thermochemical equations include heat

changes.

EXAMPLE

CH

(g) + 2O

(g)



CO

+ 2H

O

•

Exothermic – energy is a

product

•

Endothermic – energy is

a reactant

•

∆H is also called the heat

Bellwork Tuesday, January 23, 2013

• _{Begin reading the background and procedures of Part I}

• _{Turn in WS3 to the box. – Remember your seat number is}

you box number.

• _{Pick up all graded papers.}

• _{There are missing assignment reports in your bin. These}

assignments are due by Friday or they will become a zero.

• _{Remember to tell me if you want to retest. Tomorrow}

Bellwork

Wednesday, January 24

• _{A 65.0g piece of metal is heated to 78.0°C and dropped into a}

calorimeter containing 100.0g of water. The water in the calorimeter is 21.0°C. The metal and water both end at a

Bellwork, January 25

• _{A 4.92g piece of metal is heated to 108.0°C and dropped}

into a calorimeter containing 60.0g of water. The water in the calorimeter is 41.0°C. The metal and water both

Heat in Changes of State

The specific heat capacity of water is 4.18

J/g

C or 1.00 cal/g

C

The specific heat ice is 2.1 J/g

C and the

specific heat of steam is 2.0 J/g

C. This

Molar Heat of Fusion- heat required to

melt one mole of a solid (6.01 kJ/mol

or

334 J/g for water)

Molar Heat of Solidification- heat

released as 1 mole of liquid freezes.

(

6.01 kJ/mol or

334

J/g for water)

Molar Heat of Vaporization-heat

required to vaporize 1 mole of a liquid.

(40.7 kJ/mol or 2260 J/g for water)

Molar Heat of Condensation-heat

released as 1 mole of a gas

condenses to a liquid.

Heat of fusion and heat of solidification. They

are equal amounts!

To find the energy released in a phase change,

use…

q = moles x heat of phase change

Te

m

pe

ra

tu

re

is

co

ns

tan

t

du

rin

g a

ph

as

e

∆H_fus = ∆H_solid= 6.01 kJ/mol

∆H_vap = ∆H_cond = 40.7 kJ/mol

C_Ice= 2.1 J/g oC

C_water= 4.18 J/g oC

C_steam= 2.0 J/g o_C

10.4 Phase Changes

-change of physical

state

Ex. Melting, freezing,

evaporation, condensation, sublimation,

deposition

Question

•

Why is the slope between ice and vapor

Sublimation

-

Change of a solid to a

gas without going

through the liquid

phase

Deposition

is the

opposite

Ex. Iodine, ice cube

“shrinkage”, freeze

Exothermic - energy

is a product

Endothermic - energy

is a reactant

Heat

Heating/Cooling Curve

-Shows energy changes of matter. All matter

follows a curve when energy is added or lost.

Horizontal portions of the curve indicate a

physical state change. Notice that the

temperature does not change in these regions!

However, there a a change in particle position

resulting in a change in potential energy.

Ex. How much heat, in calories, is

needed to melt 150. g of ice at 0

C?

No temp change (just phase change)

Molar heat of fusion = 334 J/g for H

O

150.g ice 334 J 1 cal

g ice 4.18 J

Ex. How much heat, in calories, is

needed to heat the liquid water in the

above problem to 20.

C?

No phase change (just temp.

change)

q = mC

D

T

q = 150.g (1.00 cal/g

C)20.C

Ex. A 50. g sample of ice is held at

-10.

C. Will 270 calories of heat be

sufficient to raise the temperature of the

ice to 0

C?

just temp change

q = mC

D

T

q = 50.g (0.5 cal/g

C)10.

C

Ex. How many calories are released

when 36 g of steam at 100.

C

condenses to water at 100.

C?

just phase change

36g steam 2260 J 1 cal

g H

O 4.18J

Ex. How many calories are needed to

convert 5.0 g of ice at -15

C to steam at

130

C?

Phase changes and temp changes

q = 5.0g (1.0cal/g

C)15

C

=

75 calories

5.0g ice 334 J 1 cal

g H

O 4.18J

q = 5.0g (1.0 cal/g

C)100

C

=

500 calories

5.0g water 2260 J 1cal

g water 4.18J

=

2.7 x 10

calories

q = 5.0g (1.0cal/g

C)30

C

=

150 calores

q = 75 + 400 + 500 + 2700 + 150

Standard Heat of Formation of a compound

(

D

H

)

*

D

H

of a free element in its standard state

is zero.

*This is another way to calculate

D

H for a

reaction.

D

H =

D

H

products

-

D

H

Ex.

1. Calculate

D

H for the following reaction:

CaCO

(s)



CaO(s) + CO

(g)

∆H_fo values:

CaCO₃ = -1207.0 kJ/mol CaO = -635.1 kJ/mol

CO₂ = -393.5 kJ/mol

∆H = [-635.1 + (-393.5)] – [-1207.0]

2. Calculate the heat of reaction for the

following reaction:

2H

(g) + O

(g)



2H

O(g)

∆H_fo values:

H₂O(g) = -241.8 kJ/mol

∆H = [2(-241.8)] – [2(0) + 0]

∆H = -483.6 kJ

Bellwork

Friday, January 25

• _{Calculate the enthalpy of formation for the reaction below.} • Zn + 2HCl  ZnCl₂ + H₂

• D_{H Zn = 0.0 kJ/mol}

Bellwork

Monday, January 28

Determine if the following are

endothermic or exothermic.

•

D

H = -226.55 kJ/mol

•

D

H = -6.89 kJ/mol