Chapter 2
Matter, Forces, & Energy
2A Matter
2A Matter
2B Force and Matter
2.5 What Is a Force?
1.
2.
3.
4.
A force is a push or a pull
All forces act in pairs (ball & bat, shoes &
ground, atmosphere & skin)
Fluids can exert a lot of force
Scientists are usually only interested in
one of the pairs
2B Force and Matter
2.6 Types of Forces
1.
Contact Forces
a.
b.
c.
d.
Compression--pushes objects closer
together
Shear--causes particles in an object to
move across each other in layers
Tension--pulls on an object in opposite
directions
Friction--opposes the motion of objects
in contact
2B Force and Matter
2.6 Types of Forces
2.
Field Forces
a.
b.
c.
d.
e.
f.
Act on objects separated by a distance
The force exerted between two objects
decreases rapidly as the objects are
farther apart
A field force never disappears
Magnetic force--exerted between
magnets and magnetic metals
Electrical force--exerted between
electrical charges
Gravity--exerted by matter on other
matter
2B Force and Matter
2.7 Gravity
1.
2.
3.
4.
Caused by mass
Gives things weight
All objects exert a gravitational force
Earth’s gravity pulls objects toward the
center of the earth
2C Energy and Matter
2.8 What is Energy?
1.
2.
3.
Energy: the ability to do work
Work: a force that acts on an object as it
moves through a distance
When work is done, energy is added to or
taken away from objects
2C Energy and Matter
2.9 Kinds of Energy
1.
Kinetic
a.
b.
c.
2.
Movement
Dependent on mass (fixed) and speed
(variable)--a car going 65 mph has more
energy than that car going 30 mph
Examples: moving water, hurricanes,
tornadoes, accelerated particles
Potential
a.
b.
c.
The potential to move with a force acting
on it
Dependent on mass (fixed) and distance it
could move (variable)--a ball on top of the
gym has more potential energy than a ball
on your desk
Examples: rocks on cliffs, books on
2C Energy and Matter
2.10 Sources of Energy
1.
2.
Mechanical Energy (kinetic & potential)
Thermal Energy
a.
b.
c.
3.
Sum of kinetic & potential energy of
particles vibrating in random directions
Transfer of this energy is called heat
Example: sun, fire, stove
Sound Energy
a.
b.
c.
d.
e.
Kinetic energy of particles vibrating
repeatedly back and forth in one direction
Audible sounds: heard with unaided ear
Ultrasonic sounds: too fast to hear
Infrasonic: too slow to hear
Examples: any sound, dog whistle, longdistance elephant communication
2C Energy and Matter
2.10 Sources of Energy
4.
Electrical Energy
a.
b.
5.
Kinetic energy of ions caused by positive
and negative charges of particles
Examples: lightning, electricity
Magnetic Energy
a.
b.
Kinetic energy of electrical charges that
works on magnetic metals
Examples: refrigerator magnets, Earth,
generators, electromagnets
2C Energy and Matter
2.10 Sources of Energy
6.
Chemical Energy
a.
b.
7.
Light Energy
a.
b.
8.
Stored in bonds between atoms; released when
bonds break
Examples: coal, oil, natural gas, anything that
burns
Everything that gives off light produces light
energy
Some light energy is invisible to the human eye
(radio waves, microwaves, infrared light, UV
light, x-rays, and gamma rays)
Nuclear (new•klee•ur) Energy
a.
b.
Stored in the bonds between particles of atomic
nuclei; released when atoms are split
Examples: sun, nuclear reactors
2C Energy and Matter
2.11 Conservation of Energy
1.
2.
3.
Energy is neither created nor destroyed-it only changes from one form to
another (1st Law of Thermodynamics)
Energy may become unuseful, but it is
still there
Atomic bonds in sun->light and heat>photosynthesis->sugar bonds>organismic growth, repair,
reproduction, heat, sound->...
2D Composition of Matter
2.12 & 2.13 Atoms & Ions; Elements & Compounds
1. Atom--nucleus of
protons & neutrons
with orbiting electrons
2D Composition of Matter
2.12 & 2.13 Atoms & Ions; Elements & Compounds
2. Ion--atom that has
gained or lost an
electron to give the
atom a positive or
negative charge
2D Composition of Matter
2.12 & 2.13 Atoms & Ions; Elements & Compounds
3. Element--pure
substance made of
one kind of atom
He
He
He
He
He
He
He
He
He
He
He
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He He
He He
He
2D Composition of Matter
2.12 & 2.13 Atoms & Ions; Elements & Compounds
4. Compound--2 or more
elements bonded
2D Composition of Matter
2.14 The Structure of Matter
1. Atom--single atom
He
He
He
He
He
He
He
He
He
He
He
He He
He He
He He
He He
He He
He
2D Composition of Matter
2.14 The Structure of Matter
2. Molecule--2 or more
atoms bound (same or
different elements)
2D Composition of Matter
2.14 The Structure of Matter
3. Crystal--repeating
patterns of molecules
in rigid arrangement
2D Composition of Matter
2.15 Changes in Matter
1.
Physical Changes
a.
b.
No change in chemical composition;
change in appearance
Examples:
i. Dissolving sugar in lemonade
ii. Pureeing and mixing fruit into a
smoothie
iii. Sanding the rough spots on a
picnic table
iv. Crushing your empty soda can
v. Freezing juice into popsicles
2D Composition of Matter
2.15 Changes in Matter
2.
Chemical Changes
a.
b.
c.
d.
One substance changes into another
Combining: 2H + O = H2O
Breaking: 2H2O2 -> 2H2O + O2
Signs of chemical reactions:
i. Release of energy
ii. Temperature change
iii. Permanent color change
iv. Appearance of new or different
substance from a mixture
v. Gas is produced (not from
evaporation)
2D Composition of Matter
2D Composition of Matter
2.15 Changes in Matter
3.
Nuclear Changes
a.
b.
c.
d.
Changes at the atomic level:
i. One or more neutrons or protons
is emitted
ii. Proton-neutron transformation
iii. Gamma ray emission
iv. Large nucleus splits into two
smaller nuclei
Alpha particle--2 protons & 2 neutrons
Fission--splitting of nuclei; rare in nature
but used to generate electricity
Fusion--smashing together of 2 small
nuclei; occurs in the sun and used in
weapons
2D Composition of Matter
2.15 Changes in Matter
4.
Conservation of Matter
a.
b.
Matter can’t be created or destroyed
Matter can change forms