Download Chapter 2

Chapter 2
Matter and Energy
Energy

Energy—the capacity to do work


Where does your energy come from?
Can be in the forms: light, heat, chemical,
mechanical, electrical, and sound
Transfer of Heat



Look at your food labels—bomb
calorimeter
Heat—energy transferred between
objects that are at different
temperatures
Heat is transferred from a warmer to
cooler objects
Changes in Matter

Physical Changes



Melting
Boiling
Cutting

Chemical Changes



Cooking
Baking
Burning
Change in Energy

Evaporation—the changing from a liquid
to a gas


Energy must be put into the system to
surpass the boiling point of a liquid.
Energy may be released when going down
the phase diagram, that is from vapor to
liquid, etc.
Endothermic and Exothermic

Endothermic



Heat is ABSORBED
the system
EX: melting of ice &
boiling of water &
cold packs
Makes objects feel
cooler!

Exothermic



Heat is RELEASED
from the system
EX: freezing of water
& heat pack & glow
sticks
Makes objects feel
hotter!
Law of Conservation of Energy



States that energy (E) cannot be
created nor destroyed but can be
changed from one form to another.
The quantity of energy remains the
same.
E = mc2
Released as heat


Worst industrial
disaster: Grandcamp
in Texas in April
1947.
Cargo ship carrying
fertilizer


Kinetic E—the E of
an object that is due
to the object’s
motion
The object is
moving!
Temperature vs. Heat


Temperature—actual
measurement of the
average kinetic E of
the random motion
of particles in a
substance.
A measure of how
hot or cold
something is.


As kinetic E
increases, so does
the temperature!
Heat is the E that is
being transferred
and temperature is
the measurement!
How to express temperature

Kelvin (K):



SI unit for
temperature
At 0K, absolute zero,
all particles cease.
K = oC + 273

Celsius (oC):



0oC is the freezing
point of water
100oC is the boiling
point of water
oC
= K - 273
Specific Heat

The quantity of heat required to raise a
unit of mass of homogeneous material
1K or 1oC in a specified way.