2-1 What is Energy

CHEMICAL ENERGY

The energy that matter possesses because of its chemical makeup

Comps. have chem. energy bec. of the atoms they contain and the bonds that hold them together

CHEMICAL BOND – a mutual attraction betw. diff. atoms that binds the atoms together

KINETIC ENERGY

Energy a moving object has bec. of its motion

Atoms & molecs. are in constant motion

POTENTIAL ENERGY

energy an object has bec. of its position position of atoms

• When positions change, bonds are formed or broken & energy is absorbed or released

rxns. change positions of atoms and potential energy changes

All chemical & physical changes involve a change in energy.

freezing

evaporating

dissolving

explosion

burning

ENERGY

the capacity to do work

LAW OF CONSERVATION OF ENERGY

in any chemical or physical process, energy is neither created nor destroyed

total amt. of energy in the universe is constant

energy just changes form

Energy can be transferred.

HEAT

the sum total of kinetic energy of the particles in a sample of matter

can be transferred due to a difference in temp.

SYSTEM

a specific portion of matter in a given region of space that has been selected for study during an experiment or observation.

complex or simple

everything outside system is surroundings

Heat transfer:

System to surrounding

Surroundings to system

TEMPERATURE

a measure of the average kinetic energy of the particles in a sample of matter.

heat flows from high temp. to low temp.

Thermometer measures temp.

matter expands as its temp. incrCelsius scale.

0oC is freezing pt. of water

Kelvin scale0K is absolute zero – lowest temp. theoretically possible

oC = K – 273K = oC + 273

Diff. substs. incr. temp. diff. amt. with same amt of heat added

SPECIFIC HEAT CAPACITY (cp) – The amt. of heat energy required to raise the temp. of 1 gram of a subst. by 1K (or 1 Co)

expressed in J / g . K (or J / g . Co)

Joule (J) – SI unit of energy

Heat energy (q) = m c t

Matter and energy are closely related

Einstien – E = mc2

implies matter and energy are equivalent

can be changed into ea. other