Section One Energy

Energy: is the capacity to do some kind of work, such as moving an object. Examples:

No matter how energy is defined, it is always involved when there is a change in matter.

(Kinetic Energy: energy of motion)

(Potential Energy: stored energy)

(Joule :unit of energy see Reference Tables)

Ex:8kJ= ?J 1kJ=1000J

Changes in matter can be physical or chemical

Every change in matter involves a change in energy

The melting of ice and the boiling of water are 2 ex of phy changes that are endothermic process. Some chemical changes are also endo.

Endothermic: a process in which heat is always absorb; cooler to touch

** word heat/energy/#’s on reactant side of equation

H2O(s) + heat H2O(l) H2O(l) + energy H2O(g)

Any change in matter when heat is released is exothermic, get hotter ** heat/energy/#’s on product side

Energy is either absorbed or given off during a phy or chem change

A + B C +energy A + B+ energy C

Exo endo

Lavoisier worked on the Law of Conservation of Energy.

Defined: Energy cannot be created nor destroyed it’s rearranged.

Heat is the energy transferred between objects that are at different temperatures. Heat is transferred (flows) from a higher temperature object to a lower temperature until thermal equilibrium s reached.

Temperature: measures the average Kinetic Energy of the random motion of particles in a substance.

Temperature scales based on marking a thermometer would need: a boiling point, freezing point, find the difference between the two temperatures, and make a range to space out even.

Temperature scales:

Celsius scale 0 c (fpt/mpt of water) to 100c (bpt of water)

Kelvin Scale 273K (fpt/mpt of water) to 373K (bpt of water)

Converting Table T

K= C + 273 C= K -273

Range on both scales is 100

Ex:1 if temp changes 25c, how much will it change on the Kelvin scale?

25K

Ex 2: 47K=?C 52C=?K

-226c 325K

Absolute zero: coldest possible temperature all motion stops.

0K -273C

Terms• Melting: sl endo Heat of Fusion• Freezing: ls exo Heat of Crystallization• Boiling lg endo• Condensation: gl exo• Sublimation: sg no l phase endo

H2O(s) H2O(g) CO2(s) CO2(g) I2(s) I2(g)

Specific Heat

Table T q=mc T

Table B Specific Heat Capacity of Water 4.18 J/g*K(c)

Ex#1 a 2,000g sample of water is heated to 3c. How much heat is produced?

Ex#2 A 500. g sample of water had a temperature change from 10.c to 15c. How much heat was produced?

1. q=mc^T

40.0g x 4.18J/gc x 20.0c = 3,344J~3,340J

2. q=mc^T

65.6gx 4.18J/gc x 16.2c= 4,442J ~4,440J3. q=mc^T

275g x 4.18J/gc x 88.0c= 101,156J~101,000J4. q=mc^T

25g X 4.18J/gc X 45.0c= 4,703J~4,700J

5. q=mc^T

135.6g x 4.18J/gc x 74.2c= 42,057J~42,100JBack

1. q=mc^T

2,000.gx 4.18 x 3.0 =25,080~25,000J

5. q=mc^T

q=100.g x .129J/gC X 14C=181J~180J

6. q=mc^TQ=250.g x 4.18J/gC x 60.C= 62,700J~63,000J

7. q=mc^T5,000.g x 4.18J/gC x 60.C=1,254,000J~1,300,000J

Ex#3

A sample is heated from 20C to 100c as 70,000j of heat is released. How many grams of water were heated?

Ex#4

A 2,000g sample of water whose temperature was 50C lost 33,600J of heat over a ten minute period. What was the temperature of the water at the end?