THE LAW OF CONSERVATION

OF ENERGY

Energy can not be created or destroyed

System and Environment

System is the substance, the reaction, a process

that became the center of attention (object)

System

Environment

The environment is everything that is related

to the system

Lets check it out

Example: substance A and substance B is inserted into the test tube

System: substance A and substance B

Environment: test tubes and air

Types of system

1. Open System

If the system and the environment can

experience, exchange of matter and energy

2. Closed System

If the system and the environment can not

be exchanged material, but it can be an

exchange of energy

3. Isolated System

In system and the environment can not be

an exchange of energy and matter

The sign for the heat and work

• System received heat

• System released heat

• System does work

• System received the work

q (+)

q (-)

w (-)

w (+)

Internal Energy (E)

the amount of energy possessed by an agent or system

ΔE = EP - ER

Reaction of Heat

1. If reaction is reacting in closed system, with fixed volume (ΔV=0), where if ΔV=0 there is no work in there(w=0)

So ΔE= q

2. If reaction is reacting in opened system, with fixed pressure , where may system do or received work

So ΔE= q + w

Exothermic Reaction

• Chemical reactions that are

accompanied by the release of heat

• Release heat from system to

surrounding

• H product < H reaction

• Sign of ΔH is always (-)

Exothermic Reaction

Reactants Products + Energy

Reactants

Products

- H

Energ

y

Energy of reactants

Energy of products

Reaction Progress

Endothermic Reaction

• Chemical reactions that areaccompanied by the absorption ofheat

• Absorb heat from surrounding tosystem

• H product > H reaction

• Sign of ΔH is always (+)

Endothermic Reaction

Energy + Reactants Products

+ H Endothermic

Reaction progress

Energ

y

Reactants

ProductsActivation Energy

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THERMOCHEMISTRY

Influenced by

2 3

4

6

5

causing

9 10

involving

7 8

12 11

1

Statement to find the key-word :

1. Energy cannot be destroyed or created

2. the part of the universe on which we focus our attention in a certain experiment

3. the parts of the universe that interact instantly with the system or anything that restricts the system

4. may heat exchange between system and surrounding and matter movement

5. may heat exchange between system and surrounding and not matter movement

6. impossible for heat exchange between system and surrounding

7. subtracting the enthalpy of the reactant from the enthalpy of product

8. energy contained in a substance at temperature of 25oC and pressure of 1 atm.

9. a chemical reaction in which heat is absorbed from the surroundings

10.a chemical reaction in which heat is released from the system

11.Symbolize for enthalpy of the system falls.

12.Symbolize for enthalpy of the system rises.

THERMOCHEMISTRY

Influenced by

SYSTEM SURROUNDINGS

OPENED

ISOLATED

CLOSED

causing

ENDOTHERMIC

REACTION

EXOTHERMIC

REACTION

involving

ENTHALPY

CHANGEENTHALPY

Law of Conservation of

Energy