Transcript OGT Cram Session 3 Physical Science

Questions from the Past
Does weight affect how fast
something falls?
►No!
► Fluid
friction (Air
Resistance) does!
► Which falls faster an
elephant or a feather
with air resistance.
► If
we take away air
resistance which will fall
faster, the elephant or
the feather?
► They will fall at 9.8 m/s2
FORCES
What is a force?
1. A force causes a resting object to move, and it
can accelerate a moving object by changing the
object’s speed or direction.
B. Measuring a Force
1. Ex. A spring scale at the grocery store.
C. Unit of Force
1. Newtons = the force that is needed to move 1
Kg at a rate of 1 meter per second.
2. Named after Sir Isaac Newton.
A.
How to Draw Forces Acting on
Objects
► 12.1
Forces
D. Representing Force
1. Use arrows:
a. Direction tells you direction of force.
b. Length tells you how much force.
I.
Sliding Friction
1. Opposes the direction of motion
after an object starts moving.
2. Since Sliding friction is less than
static friction = less force is needed
to keep the object moving
Push
Sliding friction
Rolling friction – opposite force
that acts on a rolling object.
1. 100 to 1000 times less than
static or sliding friction.
K. Fluid friction – friction that acts
on an object in water or air.
L. Gravity – acts downward to the
center of the earth.
1. Gravity causes objects to
accelerate downward.
M. Push force – force makes you
go forward
J.
Draw and Label the forces acting on
a box moving to the left.
push
Newton’s 3rd
Law, ground
pushing up
gravity
Sliding friction
An object in motion wants to stay in motion. An
object at rest wants to stay at rest.
► Describe
Newton’s 1st
Law in Your Own
Words.
When something changes speed or
direction it accelerates.
► Describe
Law.
Newtons 2nd
For every action there’s an equal and
opposite reaction.
► Describe
Law.
Newton’s 3rd
Guy jumps forward, boat goes backward.
A. Gravity
D.
C.
Fluid friction (water) = opposes the velocity
fluid friction (wind) = opposes the velocity
A.
Physical Property
► Any
characteristic of a material that can be
observed without changing the composition
of the material.
► 1.
Viscosity– The tendency of a liquid to quit
flowing or its resistance to flowing.
► High
viscosity = the slower it moves
► Syrup
has a higher viscosity than water
http://plc.cwru.edu/tutorial/enhanced/lab/visco/intro/intro.htm
► 2.
Malleability– The
ability of a solid to be
hammered without
shattering
► Metals
are usually
malleable. If not, we
wouldn’t have gold
jewelry or knives!
► Other
materials break
/shatter when
hammered
►
3.Density– Ratio of an
object’s mass to volume:
Mass/volume (memorize
formula!)
►
Denser object’s sink and
less dense objects float
►
The box that has more
balls has more mass per
unit of volume. This
property of matter is called
density.
► 4.
Hardness– A material’s ability to resist
scratching
► Glass
is harder than a penny so glass can
scratch a penny
► 5.
Ductility - The ability of a substance to be
stretched; the ability for a metal to be
drawn into wire.
Protons = Positive part of nucleus
► 1.
found in nucleus
► 2. can tell you the
exact element
 Example: if you know
the element has 10
protons; you just find
element 10 on the
periodic table
► Used
to find atomic
weight
Neutrons = no charge
►
►
Used to find atomic mass
Sometimes the same
element can have different
numbers of neutrons =
ISOTOPES
 Ex. Carbon 12 has 6
neutrons; 6 protons

Carbon 14 has 8
neutrons; 6 protons
►
Proton number NEVER
changes
Electrons = negative
► Atomic
number = # of
electrons
► Found outside the
nucleus
► Weight almost nothing
 Number of electrons
plays no role in
calculating the weight
of atoms.
Valence Electrons
► Electrons
outershell
found in the
Dot Diagrams
► Tell
you number of
valence electrons
► Chlorine has 7 valence
electrons because it
has 7 dots around it
Atomic number
Number of protons
Number of Electrons
Atomic mass
Protons + Neutrons
Families
►
►
Each column is called a family.
Every family has similar characteristics
 The biggest characteristic is valence electrons
 The number of valence electrons is represented by Roman
numerals above the columns
 Noble gas have 8 valence electrons even though it has an 0
The Alkali Metals
► Have
1 valence
electron…extremely
reactive.
► The reactivity
increases from the top
of Group 1A to the
bottom.
► Li, Na, K, Rb, Cs, Fr
Alkaline Earth
►2
valence electrons
► Differences in
reactivity among the
alkaline earth metals
are shown by the ways
they react with water.
► Be, Mg, Ca, Sr, Ba, Ra
The Halogens
►7
valence electrons
► F, Cl, Br, I, At
► Despite their physical
differences, the
halogens have similar
chemical properties.
The Noble Gases
► Group
18
► The noble gases are
colorless and odorless
and extremely
unreactive.
► He, Ne, Ar, Kr, Xe, Rn
How Ions are formed!
►
►
When an alkali metal or alkaline earth metal bond with a
halogen.
The alkali metals gives a halogen an electron.
 The alkali metal becomes a cation (positive)
 The halogen becomes an anion (negative).
Covalent Bonds
► When
elements share
valence electrons
equally!!
Law of Conservation of Mass
► Chemical
Equations
 Reactants on left
 Products on right
► Number
of molecules on left has to equal
number of molecules on right
 These equations are said to be balanced.
There are six molecules of Carbon on the left, and six on the right.
pH Scale
► Tells
you how acidic or basic
► Acids
 Citrus fruits
 Batteries
 Stomach juices
► Bases




Baking Soda
Sea Water
Soap
Liquid drain cleaner
Conductivity
► The
ability to allow electricity/heat to flow.
► The more conductivity = the more room
electrons have to move.
► Was a test question a couple of years
ago……
Kinetic Energy
► Kinetic
is moving
energy.
► The faster it goes the
more energy has
► More temperature =
more kinetic energy.
Potential Energy
► Potential
Energy is essentially height!
 If it is above the ground is has potential energy.
 The higher it is the more potential energy it has
► Elastic
potential energy
 If you stretch a substance it has potential
energy
Law of Conservation of Energy
► Energy
can not be created or destroyed.
► Energy is just converted from one form to
another.
More Energy Transformations
Check out how the speed changes as
it goes down the hill
This was a test question a couple of years ago….
It asked where would the cart be going the
fastest…..it goes the fastest at the bottom!
Other Energy Conversions
► Energy
conversions
► All forms of energy can be converted into
other forms.
 The sun’s energy through solar cells can be
converted directly into electricity.
 Green plants convert the sun’s energy
(electromagnetic) into starches and sugars
(chemical energy).
Fission and Fusion
► Fission
is splitting nuclei.
 Nuclear reactions
 Nuclear bombs
 Nuclear powerplants
► Fusion
is putting nuclei of atoms together
 helium reactions in stars
Fission
This is where the most
energy is released.
Previous test question….
Fusion
Wave Properties
III. Properties of Waves
A.
Frequency, Period, and Amplitude
1. Frequency = # of cycles in a given time
2. Wavelength = is the distance between a
point on one wave and the same point on
the next cycle of the wave.
3. Amplitude = how high and low the wave
goes from the middle.
4. The more energy a wave has, the greater
is its amplitude
5. http://www.ngsir.netfirms.com/englishhtm/TwaveA.htm
IV. Behavior of Waves
A.
Reflection = occurs when a wave bounces
off a surface it cannot pass through.
1. Reflection does not change the speed
or frequency of a wave.
ex. When you throw a ball at the wall it
bounces back because it can’t go through
the wall.
Refraction = the bending of a wave as
it enters a new medium.
1. When a wave enters a medium at
an angle, refraction occurs because
one side of the wave moves more
slowly than the other side.
C. Diffraction = the bending of a wave as
it moves around an obstacle or passes
through a narrow opening.
B.
Wave Absorption
► Waves
can be
absorbed into the
medium.
 Ex. You do not want
waves to bounce
around in a recording
studio. The recording
studio walls will have
carpet on them to
absorb materials.
 Modern designs are not
good for recording
studios or music halls.
Conduction
► The
transfer of heat by
direct contact between
objects or particles.
Convection
► Heat
transferred by
the movement of
molecules within a
substance.
► Movement
occurs from
warmer areas to cooler
areas.
Radiation
► Heat
transferred
through space.
► EXAMPLE:
The sun’s
rays causing a
sunburn.
Heat/Movement
► Always
colder.
from warmer to
 Examples:
heat moves from water
to ice
► Heat moves from air to
water
►
 Adding more ice to a
glass of cold water will
just make it get cooler
faster and stay cool.
 Adding more ice does
not make something
colder!
Heat and Particle movement
ICE
WATER
STEAM
When you add heat particles
move faster!
V. Sound and Hearing
A.
B.
C.
D.
E.
Sound waves are longitudinal waves.
Sound depends on speed, intensity and
loudness, frequency and pitch.
Speed = how fast sound travels
Intensity = how loud is the sound
Frequency = how high it is or how low
it is.
Wave Superimposing on one Another
► http://www.phy.ntnu.edu.tw/ntnujava/index
.php?topic=19