unit 09 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Unit 09 PowerPoint Presentation
Download Presentation
Unit 09

Loading in 2 Seconds...

play fullscreen
1 / 36

Unit 09 - PowerPoint PPT Presentation


  • 118 Views
  • Uploaded on

Unit 09. Thermochemistry. Unit 9 Vocabulary. Thermochemistry - concerned with heat changes that occur during chemical reactions Energy - capacity of an object to do work or produce heat Kinetic energy - the energy an object has due to its motion Potential energy - stored energy

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Unit 09' - posy


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
unit 09

Unit 09

Thermochemistry

unit 9 vocabulary
Unit 9 Vocabulary
  • Thermochemistry - concerned with heat changes that occur during chemical reactions
  • Energy- capacity of an object to do work or produce heat
  • Kinetic energy- the energy an object has due to its motion
  • Potential energy- stored energy
  • Temperature- describes amount of motion of particles
unit 9 vocabulary1
Unit 9 Vocabulary
  • Heat - describes amount of energy transferred from one object to another
  • Endothermic process- heat absorbing process
  • Exothermic process- heat releasing process
  • Specific heat- Amount of heat it takes to raise 1g of a substance by 1°C
the flow of energy
The Flow of Energy

Heat is transferred from one object to another.

cranking up the heat basic thermodynamics
Cranking up the Heat: Basic Thermodynamics
  • Energy is required in all biological and chemical processes.
kinetic energy
Kinetic Energy
  • the energy an object has due to its motion

Potential Energy

  • stored energy
slide7

Energy in the universe is constant, though it changes forms.

Law of Conservation of energy – energy can neither be created nor destroyed

heat vs temperature
Heat vs. Temperature
  • Temp. and heat are not the same thing.
  • Temp. describes amount of motion of particles
  • Heat describes amount of energy transferred from one object to another
describing energy changes
Describing Energy Changes

Heat flow is from the warmer to the cooler object

Heat Flow

Heat Flow

slide10

Describing Energy Changes

Hot day 50°C = 122°F

Energy transferred from fire to beans. Change in energy for beans would be positive.

Beans lost energy, it was transferred to its surroundings. This change of energy would be negative change = ∆

slide11
Endothermic reactions – absorbs heat, ∆E is positive, the surroundings cool down

Exothermic reactions – releases heat, ∆E is negative, the surroundings heat up

Surroundings

Heat

Surroundings

Describing Energy Changes

Heat

units used to describe energy
Units used to describe Energy:

calorie – called “little calorie” – (cal)

kilocalorie – called “Big calorie”- (CAL)

1000 calories – same as a food calorie

Joule – the SI unit of heat - (J)

slide13
CONVERSION FACTOR

1 cal = 4.184 joules

1 cal 4.184 J

4.184 J 1 cal

heat units conversion problems
Heat Units: Conversion Problems

1. Convert 32.7 cal to joules.

2. Convert 6.24 J to cal.

specific heat
Specific Heat -

Amount of heat it takes to raise 1g of a substance by 1°C

Metals have a low specific heat

Water has a high specific heat

learning check
Learning Check

1. On a sunny day, the concrete deck around an outdoor swimming pool becomes hot, while the water stays cool. This is because…

A. The deck has a higher specific heat than the water

B. The deck has a lower specific heat then the water

C. Both objects have the same specific heat

learning check1
Learning Check

2. Two objects are sitting next to each other in the sunlight. Object A gets hotter than object B.

A. Object A has a lower specific heat than object B

B. Object A has a higher specific heat than object B

C. Both objects have the same specific heat

specific heat of water
Specific Heat of Water

4.18 J/g ×°C

or

1 cal/g ×°C

Matches definition: Amount of heat it takes to raise 1g of a substance by 1°C

formula for specific heat
Formula for Specific Heat

q = amount of heat – measured in cal or J

m = mass – measured in g

C = specific heat – units are J/g x °C or cal/g x °C

ΔT = change in temp – measured in °C

q = mc ΔT

specific heat problems
Specific Heat Problems:

1. Aluminum has a specific heat of 0.9020 J/g × °C. How much heat is lost when a piece of aluminum with a mass of 23.984 g cools from a temperature of 415.0°C to a temperature of 22.0°C?

2. 850 calories of heat are applied to a 250 g sample of liquid water with an initial temperature of 13.0 °C. 

Find: a) the change in temperature and

b) the final temperature. 

(remember, the specific heat of liquid water, in calories, is 1.00 cal/g x °C.)

specific heat problems1
3. The temperature of a sample of water increases by 69.5 °C when 24,500 J are applied.  The specific heat of liquid water is 4.18 J/g x °C.  What is the mass of the sample of water?

4. When 34,700 J of heat are applied to a 350 g sample of an unknown material the temperature rises from 22.0°C to 173.0°C.  What must be the specific heat of this material?

Specific Heat Problems:
bell work wed 1 23 08
Bell Work - Wed 1/23/08

When 34,700 J of heat are applied to a 350 g sample of an unknown material the temperature rises from 22.0°C to 173.0°C.  What must be the specific heat of this material?

energy and change of state
Energy and Change of State

You do not have to write this

When energy is added to a solid substance, its temperature increases until its melting point is reached. Upon the addition of more energy, the substance begins to melt.

 The temperature remains the same until all the substance has melted. ****

enthalpy of fusion d h fus
Energy required to melt 1 gram of a substance at its melting pointEnthalpy of Fusion (DHfus)

Heating Curve: ( For Water)

Temp

DHfus

Melting point

(°C)

0

-10

Heating Ice

(solid)

-20

Time

energy and change of state1
After the substance melts and if heating continues, the temperature will continue to rise until it reaches its boiling point.

۞The temperature remains the same until all the substance has boiled.***

Energy and Change of State
enthalpy of vaporization d hvap
Enthalpy of Vaporization (DHvap)

Boiling Point

100

DHfus

DHvap

Temp

Heating Water

(liquid)

Melting Point

0

(°C)

-10

Heating Ice

-20

Time

Energy required to vaporize 1 gram of a substance at its boiling point

important formulas to know
► Important Formulas to Know ◄

When a substance is being heated, use the following formula: (inclined line)

q = (m)(c)(DT)

When a substance is melting or boiling, use the following formula: (flat line)

q = (m) (DHfus or DHvap)

slide28
q = (m)(c)(DT)

(C) = Specific Heat:

- of ice = 2.06 J/g x °C

- of water = 4.18 J/g x °C

- of steam = 2.02 J/g x °C

q m d h fus or d h vap
q = (m) (DHfus or DHvap)

Enthalpy Values for Water:

DHfus = 334 J/g

DHvap = 2260 J/g

sample problem 1
Sample Problem #1

How much heat is required to melt 5.67g of ice?

Q = (m)(ΔH fus)

Q = (5.67g)(334 J/g)

Q =

sample problem 2
Sample Problem #2

How much energy is required to boil 85g of water?

sample problem 3
Sample Problem #3

How much energy is required to raise the temperature of 25g of water from 15°C to 75°C ?

sample problem 4
Sample Problem #4

How much energy is required to convert 40g of ice at -10°C to steam at 150°C ?

Use Both Formulas

Draw a graph

sample problem 5
Sample Problem #5

What is the final temperature when 1250 J of energy is added to 15g of water at 25°C ?

warm up
Warm Up

How much energy is required to boil 50 grams of water?

What is the final temperature when 2500 J of heat is added to 35 grams of water at 15 degrees Celsius?

How much energy is required to convert 75 grams of ice at -20 degrees Celsius to steam at 125 degrees Celsius? (Hint: This problem has 5 steps!!)