Topic: Energy

Do Now: 1. Take out HW and open up your notes from yesterday

All physical & chemical changes are accompanied by change in energy

The chemistry of energy changes is known as Thermochemistry!

Energy: Ability to do WorkThe SI unit for an energy

measurement is called the Joule (J)

EXAMPLE: 1 Joule = amount of energy required to lift a golf ball 1 meter

Other Energy Units: calorie, Calorie, BTU’s

1 calorie = 4.18 Joules

1 Calorie = 1000 calories = 1 kilocalorie

There are 2 types of energy (we are going to draw another chart – like the on we did for matter – in our notebook

(Not a complete list!)

Energy

Mechanical – large enough to see

Kinetic Potential

Non-mechanical – too small to see

Chemical Heat Light Electrical Nuclear

Kinetic Energy (KE) – makes things move

• KE = ½ x Mass x Velocity2 = ½ mV2

• KE depends on how heavy and how fast

Potential Energy (PE): stored energy of matter

• When Potential energy is released from matter it becomes kinetic energy

Chemical Energy

• energy stored in bonds; it is released as the result of a chemical reaction

Heat Energy

• Energy related to the changes in temperature

Light Energy – makes things visible

Electrical Energy – result of the flow of electrons

Nuclear: energy is released by the change in the nucleus of an atom (can be very explosive)

Law of Conservation of Energy

• Energy is neither created nor destroyed in ordinary chemical or physical change

Energy before = Energy after

Energy can be converted from one form to another

- potential to kinetic - radiant to electric- electric to heat - chemical to kinetic- chemical to electrical

Energy of Universe is conserved

Universe

EnvironmentEnvironment

System

Energy

Energy can move between the system and the environment

Two ways to classify chemical reaction:

1. energy (heat) is given off = exothermic

2. energy (heat) is absorbed = endothermic

Exothermic – releases heat to environment

QUESTION: What happens to the temperature of the environment?

QUESTION: What happens to temperature of system?

a

Environment

System

Energy

EXO - energy leaves system (exits)

Temperature of environment

Temperature of system

Endothermic – heat is absorbed by the system

QUESTION: What happens to the temperature of the environment?

QUESTION: What happens to temperature of system?

Endo - Energy enters system (enter)

Environment

System

Energy

Temperature of environment

Temperature of system

• Note: Heat flows from hotter object to cooler object

• Example; Cold pack on leg: Heat flows from the leg to the cold pack!– Leg cools down; cold pack warms up

GAS

LIQUID

SOLID

ENDO

EXO