Physical Science Final Exam Review 2015 · She put food coloring into 4 identical bowls of mashed...
Transcript of Physical Science Final Exam Review 2015 · She put food coloring into 4 identical bowls of mashed...
J.Stevens, 2015 1
Physical Science
Final Exam Review 2015
Semester 1 Material:
Unit 1 – Nature of Science and Scientific Method
Notes:
What is science?
Science is….
Observable Testable
Measureable Limited to the Natural World
A search for understanding Open to change
Creative Repeatable
Science is not…
Based on belief Fair
Certain/absolute Based on authority
Based on proof A way to explain supernatural, or other ways
of knowing, such as art, philosophy or religion
Pseudoscience: claims to be scientific, but doesn’t follow scientific guidelines.
Example: astrology
Theory vs. Law:
Theory:
• Single explanation that is supported by lots of evidence collected over a long period of time
• Starts as a hypothesis
• It can be added to or disproven
• Theories do not become laws, theories explain laws
• Example- Theory of Evolution, Theory of Plate Tectonics
Law:
Prediction of “what”
– describes a pattern in nature
• Describes how something behaves, formula that tells us what things will do
• A truth that is valid everywhere in the universe
• It does not provide any explanations like a theory does
• Not all scientific laws have accompanying explanatory theories.
• Example- Gravity is an example of a scientific law because no experiment has been done to disprove it.
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Steps of the Scientific Method
1. Make an observation.
2. Ask a question (what’s the problem?) / Do research.
3. Form a hypothesis
4. Test your hypothesis – Experimentation
5. Collect data / Results
6. Analyze and Conclude
7. Repeat
Step 1: Observation vs. Inference
What is an observation?
Definition: describing something using your senses, computer tools, research
What is an inference?
Definition: logical prediction based on an observation
Step 2: Question / Do research
How can you do research?
Examples:
Computer
Interviews
Library
Periodicals
Step 3: Form a hypothesis
What is a hypothesis?
Prediction based on prior knowledge and creativity – NOT an edeucated GUESS!
Usually an If….then…. statement
Testable!
Step 4: Test…Experiment!
What materials do I need?
What is my procedure?
Should be written in list format, like a recipe. Someone else should be able to copy your experiment based
on your procedures.
Variables
Independent variable (IV): what you or the tester changes
Dependent variable (DV): what you are measuring
Control Group: a neutral point of reference to compare data against….the normal. Not required for every
experiment.
Constants: variables that remain the same. Example: amount of water and sunlight I give my plants when
I’m testing which fertilizer makes them grow best. I give my plants all the same amount of water and
sunlight.
Example 1
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Identify the IV, DV, control and constants for the following:
You decide to clean the bathroom. You notice that the shower is covered in a strange green slime. You decide to
try to get rid of this slime by adding lemon juice. You spray half the shower with lemon juice and spray the
other half with water. After 3 days of spraying equal amounts 3 times a day, there is no change in the
appearance of green slime on either side of the shower.
IV?
DV?
Control group?
Constants?
Example 2
Identify the IV, DV, control and constants for the following:
Marissa wanted to find out if the color of food would affect whether kindergarten children would select it for
lunch. She put food coloring into 4 identical bowls of mashed potatoes. The colors were red, green, yellow and
blue. One bowl of mashed potatoes was left as the regular white color. Each child was able to choose which
color they wanted. Each day she recorded the choice of 100 different students. She did this for 5 days.
IV?
DV?
Control group?
Constants?
Step 5: Collect Data / Results
What kinds of data do I collect and how do I define them?
Quantitative: a number, measureable, countable
Qualitative: description
Examples:
Quantitative: The U.S. Flag has 50 stars on it and 13 stripes.
Qualitative: The U.S. Flag is red, white, and blue.
Step 5 continued: Organize data
How can I organize my data?
Table
Graph (dependent variable: y-axis, independent variable: x-axis
How do I know when to use a certain kind of graph?
Line:
Comparing 2 variables
Bar:
Comparing Quantitative vs. Qualitative data, bars don’t touch
Pie/Circle:
Showing proportions of a whole or percentages
Histogram
Frequency distribution---bars touch
Step 6: Analyze and Conclude
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Analyze data:
What are graphs actually telling you?
Does data support or reject your hypothesis?
Conclusion:
Summarize your results.
Answer your question. Was your hypothesis supported?
What could you change for next time, to make your experiment better, more valid?
If your hypothesis isn’t supported, how would you change it or revamp your experiment?
What future research would you do?
Step 7: Repeat
All scientific experiments must be repeatable. They are subject to peer review and others must be able to
perform your experiment and repeat your results.
Unit 2: Composition and Properties of Matter Review
Elements, Compounds, Mixtures and Physical/Chemical Properties and Changes
Notes:
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Vocabulary:
Matter: has mass and takes up space (pure substances and mixtures)
Pure Substances: composition definite, elements and compounds
Elements –
made up of 1 kind of atom
can’t be broken down into a simpler substance
on the periodic table
example: oxygen, copper, iron
Compounds –
two or more elements chemically combined, example: NaCl (sodium and chlorine =
salt).
Often ends in “ide”
Have a definite and fixed ratio, in water there are 2 hydrogens and 1 oxygen (H2O)
Compound has different properties than the elements its made of. Ex: NaCl, Sodium or Na is a metal,
while Chlorine is a poisonous gas…but when chemically combined, they form salt…which we eat!
Mixtures: composition variable (homogeneous or heterogeneous).
Mixtures are formed simply by blending two or more substances together in some random
proportion without chemically changing the individual substances in the mixture. Mixtures can be separated
because they are only physically bonded, not chemically bonded.
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Mixtures can then be broken down into homogeneous and heterogeneous.
A homogeneous mixture or solution: these are well mixed, where you can’t see the particles and they
have a constant composition throughout.
o Examples: salt-water, kool-aid, air we breathe, alloys (metal mixtures),
o Can be two gases (air), two liquids, gas in liquid (carbon dioxide in soda), solid in liquid (salt in
water), or two solids (an alloy, gold and copper)
o Solute: the substance being dissolved
o Solvent: the substance doing the dissolving. Water is a polar molecule (positive on one end
and negative on the other) and is known as the universal solvent.
o Non-polar solvents are toxic, flammable and generally dangerous.
o Colloid: a type of mixture with larger particles, but they are not heavy enough to settle out. A
way to detect a colloid is that you can see light scatter through them. (in regular solutions, you
can’t see light through them).
Examples: milk, fog, Jell-O
The scattering of light by colloids is called the Tyndall Effect.
A heterogeneous mixture: These have areas with differing compositions, and are not well-
mixed (you can usually see the separation of the different substances).
o Examples: salt with sugar (no water), water with gasoline or oil, salad, trail mix, stew, Raisin
Bran cereal
o Suspension: a heterogenous mixture containing a liquid in which visible particles settle.
Example: Pond water, orange juice with pulp
Some ways to speed up the rate of dissolving in most solutions:
Stirring
Temperature
**the exception to these rules are if you are dissolving a gas in a liquid. Gases dissolve faster if a
liquid is cooled.
Some ways to separate mixtures:
Evaporation
Distillation
Centrifuge
Filter/sort
Magnetism
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Physical and Chemical Properties/Changes
Physical Property (a characteristic of a
material that you can observe without
changing the identity of the substances that
make up the material)
Chemical Property (characteristic of a
substance that indicates whether it can/cannot
undergo a certain chemical change, anything
that has to do with a reaction or inability to
react)
Color Density Flammable/Combustible
Shape Boiling point Reaction to light
Size Freezing point Corrosive
Volume Solid/liquid/gas Reaction to vinegar, acid, oxygen…any type
of ability to react or not react
Physical Change (no changes occur in the
structure of the atoms or molecules
composing the matter. The substance is still
the same substance as it was before the
physical change occurred)
Chemical Change (rearrangement of bonds
between the atoms occurs. This results in new
substances with new properties).
Rip/ tear/ cut Change in state (from
liquid, gas or solid)
Burning
Color change Boiling Rusting
Stretching /
folding
Freezing React with something
Mix Melting **Some indicators of a chemical change are
smell, burning, bubbles….but the only way
to be sure a chemical change has occurred
is if a new substance is formed.
How does temperature affect chemical changes?
Increasing the temperature will cause chemical changes to occur faster.
Decreasing the temperature will cause chemical changes to occur slower.
Law of Conservation of Mass:
Matter: has mass, and takes up space
Mass: amount of matter in an object
Law of conservation of mass: matter, during a chemical change, can neither be created nor destroyed, it just
changes form. Also applies to a physical change, since during a physical change matter is neither being
created or destroyed, it may just look different.
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Water and Carbon Cycles:
Biogeochemical cycles:
The Carbon Cycle:
The carbon cycle is a complex biogeochemical cycles, where carbon moves by various processes through different
reservoirs. In the above picture, the process represented by the letter A is respiration. Respiration is where carbon
dioxide leaves plants or animals and enters the atmosphere. B represents the process of photosynthesis, where plants
take in carbon dioxide to aid in the process where they can make sugars, or food. C represents a process called
decay, where organic matter is broken down by tiny microbes and released as carbon into the geosphere, and/or the
atmosphere.
Humans are affecting the carbon cycle in two major ways. The first is through land use. When we destroy forests of
trees, this upsets the carbon flow in that area. The same thing is happening when we build massive buildings and
parking lots, destroying natural vegetation. The second is through the burning of fossil fuels. We are digging up
organic material that took millions of years to form, and burning it to provide energy for us.
The Water Cycle:
The water cycle is how water moves through all the various areas of the Earth. The water cycle consists for five
main components: evaporation, condensation, precipitation, transpiration, and runoff. Because of the water cycle, it
is true that the water we have today has been around for a very long time. It simply continues to get cycled through
earth’s atmosphere and bodies of water.
Unit 3 – States of Matter (kinetic molecular theory, heat and phase changes)
4 Basic types of matter:
Solid: Particles are tightly compact, vibrate but can’t move around (low Kinetic energy - KE), definite shape
and volume
Liquid: Particles are still close together, but can move around (higher KE), No definite shape, but definite
volume
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Gas: Particles can easily spread out or move close together, particle move freely and with a lot of energy (high
KE), no definite shape or volume
Plasma: Very high KE; particles collide with enough energy to break into charged particles (+ / -), Gas-like,
indefinite shape & volume, this form is not too common on Earth, however it is the most common form of
matter in the universe, Examples: stars, florescent and neon lights, lightning.
Kinetic Molecular Theory (KMT)
– Tiny, constantly moving particles make up all matter.
– The kinetic energy (motion) of these particles increases as temperature increases.
– These particles are colliding with each other and the walls of their container (creates pressure).
Define “Heat”:
movement of thermal energy (energy inherent to an object) from a substance at a higher
temperature to another substance at a lower temp
Three kinds of heat transfer.
a. Conduction – transfer of heat energy from one particle to another by direct contact. (Primarily
in solids)
b. Convection – transfer of heat energy in fluids-gases and liquids) through the bulk movement of
matter from one place to another. (Produces currents)
c. Radiation – transfer of energy through electromagnetic waves. (Matter is not required!)
(Radiant & infrared radiation from the sun)
What happens when you put ice in a warm soft drink?
The heat energy moves from the soft drink into the ice by conduction (particle to particle
contact) causing the kinetic energy in the molecules of ice to increase, which makes the ice melt.
Pressure: Pressure = Force / Area. Pressure is created by molecules colliding with each other and the walls
of their container. Pressure can be affected by volume, temperature, and number of molecules.
Boyle’s Law:
Volume of a confined gas is inversely proportional to the pressure exerted on the gas (as
pressure is increased, volume is decreased at the same rate and vice versa)
This is true as long as temperature is constant
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Charles’ Law:
• Volume of a gas increases with increased temperature. (Gases expand with heat). Volume and
temperature are directly proportional – meaning they increase or decrease together at the same rate.
Phase Changes: When matter turns from one form to another (example, water, a liquid freezing turning
to ice, a solid).
Unit 4 - Atoms
Structure of the Atom
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Matter is anything that has mass and takes up space. Atoms are the smallest units of matter that something can
be divided into while still retaining its properties. Atoms are made of main particles, called sub-atomic
particles. They are protons, neutrons, and electrons.
Protons: Neutrons: Electrons
- positive charge - no charge (neutral) - negative charge
- in the nucleus - in the nucleus - outside the nucleus,
- is = to the atomic number - contributes to the atomic mass in a “cloud”
- contributes to the mass - atomic mass – protons = neutrons - insignificant mass
- **determines the element - **determines isotopes - in neutral atom = the
number of protons
- forms bonds
- *when electrons leave
or join an atom, ion is formed Nucleus: center of the atoms, made of protons and neutrons
Atomic Mass Unit (amu): a proton and a neutron each have a mass of 1 amu
***Mass Number = protons + neutrons (will ALWAYS be a whole number, no decimals)
***Atomic Mass = the mass on the periodic table, the average of all the isotopes of an element, will have a
decimal point.
Ions: an atom or molecule where the total number of electrons is not equal to the total number of protons,
giving the atom a positive or negative overall charge. ***So, whenever protons ≠ electrons, you have an ion.
An ion is only created when electrons leave or join an atom—nothing to do with protons leaving or
joining.
Acids and Bases: A measure of Hydrogen ions (H+). Acids have more Hydrogen ions. We measure them
using a pH (potential Hydrogen scale). The scale ranges from 0 – 14, where 0 is a strong acid, 7 is neutral and
14 is a strong base.
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Forces In the Atom
1. Gravitational Force – Attraction of objects due to their mass
a. Depends on the distance and masses of the objects
b. Weakest Force
2. Electromagnetic Force
a. Like Charges repel
b. Unlike charges attract
c. Responsible for keeping the electrons around the nucleus
3. Weak Nuclear Force
a. This force plays a key role in the possible change of sub-atomic particles.
b. The force responsible for radioactive decay
4. Strong Nuclear Force
a. Holds the atomic nucleus together
b. Counteracts the electromagnetic force.
Periodic Table:
1. Groups:
Vertical columns of elements with similar properties
Numbered 1 – 18
Elements in same group, have the same number of electrons in outer energy level (valence electrons)
Example: Every element in group 1, has 1 electron in its outer shell, every element in group 2, has 2
electrons in its outer shell, and so on (excluding transition metals)
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****Remember: Valence Electrons are electrons in the last “shell” or energy level of an atom
Important because:
• Determine an elements ability to “bond” with another element
• Chemical properties depend almost entirely on the configuration of the outer electron shell
(reactivity, flammability, etc.)
Periods:
• Horizontal rows of elements that contain increasing numbers of protons and electrons
• Numbered 1 – 7
• Each row in a period ends when an outer energy level is filled
• Example: Every element in the top row has 1 orbital for its electrons, 2nd
row has two orbitals
and so on
Categories of elements in the periodic table:
Alkali Non-Metal
Alkaline Earth Halogens
Transition Metals Noble Gas
Basic metal Lanthanide (rare-earth) - radioactive
Semi metal Actinides (rare-earth) - radioactive
3 Main Categories (you have to know!!!!)
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Metals:
• Good conductors of heat and electricity
• All but Mercury are solid at room temp
• ***Metals are located to the left of the stair step
• Alkali Metals – (Group 1) are the most reactive of all metals; don’t occur in nature in their element form
• Alkaline Earth Metals – (Group 2) shiny, ductile and malleable; combine readily with other elements
• Transition Metals – (Group 3 – 12) most familiar metals because they often occur in nature uncombined
• Inner Transition Metals
• Lanthanide Series – elements with atomic # 58-71
• Actinide Series – elements with atomic # 90 - 103
Non-Metals:
Elements that are:
• usually gases or brittle solids at room temp,
• are poor conductors
• ***located to the right of the stair step
• Noble gases – (Group 18) exist as isolated atoms. They are all stable because the outer energy level is
filled.
Metalloids:
• ***Elements that make up the stair step
• Have metallic and non-metallic properties (share characteristics with metals and non-metals)
• Part of the mixed groups (groups 13, 14, 15, 16 and 17) – which contain metals, non-metals and
metalloids
How to read the periodic table: (KNOW THIS)
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Semester 2 Material:
Unit 5: Chemical Bonds & Reactions
How do atoms stay together?
Chemical Bonds
o A force of attraction that holds two atoms together
o Has a significant effect on chemical and physical properties of compounds
o involves the valence electrons
Counting Valence Electrons
How do I determine the Number of Valence Electrons by Using the Periodic Table?
Use the Group Number!!
The Octet Rule
Atoms will combine to form compounds in order to reach eight electrons in their outer energy level.
Atoms with less than 4 electrons tend to lose electrons.
Atoms with more than 4 electrons tend to gain electrons.
Atoms with exactly 4 electrons tend to gain electrons.
There are always exceptions!
Lewis Structure or (Electron Dot Diagram)
a way of drawing the Valence electrons (outer energy level) of an atom
The symbol for the element surrounded by as many dots as there are electrons in its outer energy
level (valence electrons)
Examples:
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3 Types of Chemical Bonds
Ionic
Covalent
Metallic
Ionic Bonds
The force of attraction between oppositely charged ions.
Occurs after a transfer or loss/gain of electrons
Forms between metals and non-metals
Resulting compounds have a name that usually ends in –ide
Taken, not shared!
**** Make sure you know how to identify, draw, and write the formula for these types of bonds
using two different colors, just like on our bonding basics worksheet.
Covalent Bonds
A force that bonds two atoms together by a sharing of electrons
Each pair of shared electrons creates a bond
Forms between non-metals
Types of Covalent Bonds
o Different covalent bond types share a different number of electrons
Single covalent bond: share two valence electrons
Double covalent bond: share four valence electrons
Triple covalent bond: share six valence electrons
o Example: CO2, shares double covalent bonds
**** Make sure you know how to identify, draw, and write the formula for these types of bonds
using two different colors, just like on our bonding basics worksheet.
Metallic Bond
A force of attraction between a positively charged metal ion and the electrons in a metal
Many metal ions pass along many electrons
Many properties of metals, such as conductivity, ductility, and malleability, result from the freely
moving electrons in the metal
Water
Covalent bonds bond they hydrogens to the oxygen
Hydrogen bonds bond water molecules to other water molecules. This creates special properties:
o Cohesion: when water molecules stick to each other
o Adhesion: when water molecules stick to another substance
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Chemical Reactions
Chemical Change occurs
Atoms are rearranged, and chemical bonds are broken and reformed
One or more substances change to produce one or more different substances
Chemical Equation
Shorthand form for writing what compounds are used to begin the reaction and what compounds are
formed after the reaction occurs
Example: ***Know this:
Sr + 2H2O(l) Sr(OH)2 + H2(g)
A B
Where:
A = reactants
B = products
C = coefficient
D = gas
E = yield
F = subscript
Practice
In CO2 (carbon dioxide) how many Carbon atoms are there? How many Oxygen atoms?
1 Carbon atom, 2 oxygen atoms
In 2NH3, (windex) how many Nitrogen atoms are there? How many Hydrogen atoms?
2 Nitrogen atoms, 6 Hydrogen atoms
In 3CHNaO3 (Alka Seltzer), how many of each type of atom is there?
3 Carbon, 3 Hydrogen, 3 Sodium (Na), 9 Oxygen
In 2Sn(NO3)2 how many of each type of atom is there?
2Sn, 4N, 12 Oxygen
Energy and Chemical Reactions
Exothermic Reaction:
C E F D
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A chemical reaction in which energy is released (in the products)
The products have greater bond energy than the reactants
Example:
C6H12O6 + 6O2 6CO2 + 6H2O + energy
Endothermic Reaction:
A chemical reaction in which energy is absorbed (in the reactants)
The products have lower bond energies than the reactants
Example:
6CO2 + 6H2O + energy C6H12O6 + 6O2
(photosynthesis)
Rates of Chemical Reactions (RX)
Temperature –a measure of the average kinetic energy of the particles in a sample of matter
Ex. Increasing the temperature when cooking increases reaction rate
Surface area – amount of material that comes into contact with the reactants
Ex. Cutting a potato into smaller pieces when cooking (larger surface area (smaller pieces) increases
reaction rate)
Concentration – amount of substance per volume
Ex. Turning the valve on a gas stove to increase the concentration of methane molecules (this will increase
the rate of rx)
Ex. Too much salt in a glass of water will decrease the rate of rx
Catalysts (enzymes) –substances that help speed up chemical reactions, but are not consumed in the reaction
Inhibitors – substance that delays, slows or prevents a chemical rx; can make rx more controllable
Law of Conservation of Mass
Proposed by Antoine Lavoisier
In a chemical reaction, atoms are neither created nor destroyed
All atoms present in the reactants are also present in the products
Chemical equations must account for/show the conservation of mass balancing equations
Types of Chemical Reactions
Synthesis (creating)
o Two substances combine to make a new substance
o Ex: Synthesis of Carbon Dioxide
2CO(g) + O2(g) → 2CO2(g)
Decomposition (separating)
o A complex substance gets broken down to form two separate substances
o Ex: Electrolysis of water to make hydrogen and oxygen
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2 H2O ---> 2 H2 + O2
Combustion (burning)
o Always involves O2 (Oxygen)
o Oxygen reacts with another element or compound to form water (H2O), carbon dioxide (CO2)
and heat
o Exothermic Reactions
Single Displacement/replacement (switching)
o Two types: Single replacement and double replacement
o Single replacement (substitution): One element trades places with another element in a
compound
o Double Replacement: involves two replacements to form two entirely new compounds
Chemical vs. Nuclear Reaction
Chemical Reactions:
Rearranging, breaking and forming chemical bonds.
Involves valence electrons
Nuclear Reactions:
Involves the nucleus of atoms
Creates enormous amounts of energy
Two types:
o Fission: when an atoms nucleus gets split apart creating two new elements
o Fusion: when two atomic nuclei get smashed together, and stay together creating one new
element
Unit 6: Speed, distance, time
and Newton’s 3 laws of motion
Vocabulary Words and Formulas:
Acceleration: the change in speed over time. Formula is: (vf – vi / t) , where vf is final velocity, and vi is initial, or
beginning, velocity. Units of acceleration are always m/s2
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Practice problem: A helicopters speed increases from 25 m/s to 60m/s in 5 seconds. What is the acceleration
of this helicopter? Using the formula : (vf – vi / t), plug in the numbers. 60m/s – 25m/s = 7 m/s2
5 seconds
Average Speed: How fast something moves over a certain distance (total distance divided by total time)
Balanced Force: Forces that are equal in size and in opposite directions (creates no movement or acceleration of an
object)
Constant Speed: when speed stays the same
Displacement: the distance and direction of an objects change in position from the starting point
Distance: The length of space between two points or how far an object has moved (measured in meters)
Force: A push, pull or anything that has the ability to change motion
Friction: the force that results from relative motion between objects (like the wheel and axle of a car, or a stick and rock
rubbing together to make fire.)
Gravity: attractive force between any two objects that have mass
Inertia: The reluctance of a body to change its state of motion (related to the mass of an object), the more mass
something has, the more inertia it has…or the more force is needed to make it “move”
Instantaneous Acceleration: Acceleration at a given point in time
Instantaneous Speed: the speed of an object at a specific point in its journey
Mass: the amount of matter an object has
Momentum: the mass of an object multiplied by its speed (p=mv)
Motion: occurs when an object changes position, or moves
Net Force: the amount of force that overcomes an opposing force to cause motion; this can be zero if the opposing forces
are equal or balanced
Newton’s 1st Law (Law of Inertia): an object at rest stays at rest / an object in motion stays in motion unless acted on by
an outside force
Newton’s 2nd
Law: F = ma, where F is a force, m is a mass, and a is acceleration.
Newton’s 3rd
Law: For every action there is an equal and opposite reaction.”
Reference Point: the starting point
Sir Isaac Newton: Scientist and mathematician who discovered the laws of motion
Speed: movement from one place to another over time, S = d/t is the formula.
Practice problem: What is the average speed of a car that traveled 300 miles in 5.5 hours?
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S = d/t so S = 300 miles = 54.54 miles/hour
5.5 hours
Unbalanced Forces: Forces that are not equal in size, and are opposite in direction causing one object to move or
accelerate
Velocity: describes movement from one place to another over time and in a certain direction. Formula: v = d/t
1. Practice problem: A scout troop hiked 5.8 km southeast in 1.5 hours. What was the troops velocity? (Hint:
include direction).
v = d/t so v = 5.8km southeast = 3.86 km/hour southeast 1.5 hours
Weight: a force that gravity puts on an object; we measure it on a scale.
Unit 7: Work, Power and Energy
(use your book as review!!!) What is work?
In physics: Work is the transfer of energy that occurs when a force makes an object move
For work to be done, something has to move and the motion must be same direction as force.
When work is done a transfer of energy always occurs
How is work measured?
Work (Joules) = Force (Newtons) * Distance (Meters)
W=F * d
Example: You push a wheelbarrow with a force of 100N. You moved the wheelbarrow 5m. How much work
did you do?
1. W=F*d
2. W= (100N) * (5m)
3. W=500 J
***How much work would be done if the wheelbarrow didn’t move? 0 Joules! Since W=F*d, if d is 0, then
work is 0!
What is power?
Power – the rate at which work is done
How do I calculate power?
Power (watts) = work (J) / time (s)
P=W/t
Ex: You do 900J of work moving a couch. It took 5 seconds. What was your power?
P=W/t
P= 900J/5s = 180J/s= 180 watts (W)
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Six Kinds of Simple Machines
1. Lever
2. Inclined Plane
3. Wedge
4. Screw
5. Wheel and Axle
6. Pulley
What is a Lever?
Lever: has a fixed arm that turns around a point called the fulcrum; can help lift a heavy weight with less effort ,
or transmit a force
Ex: A hammer is a lever that helps do work.
What is an Inclined Plane?
Inclined plane: any slope or ramp that makes it easier to lift something
Ex: A ramp is an inclined plane.
You can use an inclined plane to help move an object to a higher or lower place.
What is a Wedge?
Wedge: made of two inclined planes , placed back to back, and used to push objects apart
Ex: A doorstop is a wedge.
An axe is a wedge that splits wood.
What is a Screw?
Screw: an inclined plane wrapped around a cylinder, used to hold objects together.
Think about your desk.
Does it have screws helping to hold it together?
What is a Wheel and Axle?
Wheel and axle: made of a wheel connected to a shaft (axle); used to carry loads around easily for long
distances with less effort; Gears are in this category.
The axle, or rod, turns when you put force on the wheel.
You probably have seen a wheel and axle on scooters, cars, roller skates, and wagons.
What is a Pulley?
Pulley: uses rope and a wheel to raise, lower, or move a load
The rope fits around the edge of the wheel.
You can use a pulley to move a load up, down or sideways.
What This Means
Simple machines are important to us in our daily life.
They help us do work.
They make our lives easier.
When two or more simple machines are combined to do work, they are called compound machines.
What is Energy?:
Energy is: the ability to do work and makes change possible – whenever work is done, energy is transferred
from one system to another system.
Energy is measured in Joules (J), just like work.
Energy can be calculated whether the object is in motion or at rest.
There are 2 main types of energy: Potential energy and Kinetic Energy
Potential Energy
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Stored energy that could do work
4 types:
1.Chemical: stored in the bonds of atoms and molecules, ex: batteries, coal, petroleum, natural gas, food
2. Mechanical: sum of an objects potential and kinetic energy, “ability to do work”, ex: bulldozer
3. Nuclear: stored in the nucleus of an atom, ex: fission (nuclear power plant), ex: fusion (the sun)
4. Gravitational Energy: stored in an object’s height. The higher and heavier an object, the more energy is
stored.
Ex: a large boulder at the top of a hill
Formula: Grav PE= mgh
m=mass
g=free-fall acceleration or gravity. On Earth, 9.8m/s2
h=height
Problem: A 65 kg rock climber ascends a cliff. What is the climber’s gravitational potential energy at a
point 35 m above the base of the cliff?
PE = mgh
m=65kg, g=9.8m/s2, h=35m
65*9.8*35= 22,295 J
Kinetic Energy (6 Kinds)
1. Heat energy: the vibration and movement of atoms and molecules within substances.
Ex: as an object heats up, its atoms and molecules move faster and collide more (kinetic molecular
theory)
Ex: Boiling water
2. Sound energy: produced when a force causes an object or substance to vibrate. Sound energy is transferred
through the object in a wave.
Ex: this is how we hear each other when we talk
3. Electrical energy: movement of tiny charged particles called electrons, typically moves through a wire.
Ex: electricity
What is an example in nature? lightning
4. Motion energy: movement of an object. The faster the object moves, the more motion energy it has.
Ex: running
5. Magnetic energy: closely related to electrical energy. When electrons move through a wire, a magnetic field
is created around the wire.
Ex: metals, like iron, can be turned into a magnet when a wire carrying electrons is wound around the
metal
6. Light energy: electromagnetic radiation that comes from light (travels in waves) – makes things visible
Ex: flashlight
Kinetic Energy Formula:
Formula: KE = ½ mv2
KE (kinetic energy) = ½ mass * velocity2
Ex: What is the kinetic energy of a 44kg cheetah running at 31 m/s?
KE = ½ (44kg)(31m/s)2
KE = 21,142 J
You try:
A bowling ball travelling 2.0m/s has a mass of 5kg. What is the energy of the bowling ball?
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Law of Conservation of Energy
Energy cannot be created or destroyed
The total amount of energy in the universe never changes, although energy may change form from one
form to another….energy never disappears.
Ex: Potential energy can become kinetic energy, and kinetic energy can become potential energy.
Ex: A rollercoaster: as the rollercoaster rolls, it loses energy due to friction and air resistance. But that energy
doesn’t disappear, it gets converted to different forms of energy.
Heat energy from friction causes an increase in the temperature of the track, the car wheels and the air.
Some energy compresses the air and causes a roaring sound.
When energy seems to disappear, it is really just changing forms. Almost always, heat is lost.
Renewable Energy – 5 Kinds
Sun: clean, abundant renewable energy from the sun
Wind: energy from air in motion.
Water (Hydropower): energy created from swiftly flowing water in a big river. Also uses waves and tides.
Geothermal: Heat from within the earth.
Biomass: organic material made from plants and animals. Biomass contains stored energy from the sun.
Ex: wood, crops, manure, and garbage.
**Most energy in the U.S. currently comes from fossil fuels…which are non-renewable and will eventually run
out.
Unit 8: Waves and Sound
What is a wave?
A wave is a disturbance that carries energy through matter or space.
Waves transfer energy
o Remember energy is the ability to do work, or apply a force over a certain distance.
o The bigger the wave, the more energy it carries.
Energy Spreads as Waves Travel
Think of standing right next to a speaker at a concert…the sound may damage your ears! But if you
stand 100 m away, the sound is harmless. Why?
o As sound waves travel, the waves spread out in spheres…as the spheres get bigger, there is
the same amount of energy, but it is more spread out.
Vibrations and Waves
Most waves are caused by vibrating objects.
Speaking or singing: vocal cords move back and forth. That motion makes the air in the throat
vibrate, which creates sound waves that eventually reach your ears.
The vibration of the air in your ears causes your eardrums to vibrate.
Mechanical vs. Electromagnetic
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Electromagnetic waves:
• Do not require a medium
• Consists of oscillating electric and magnetic fields which radiate outward at the speed of light
• Light: can travel from the sun to earth through empty space
Mechanical waves
• Require a medium (or substance) to travel through
• Examples: earthquakes: waves that travel through earth; Ripples: travel through water; sound: travels
through air
How do we classify mechanical waves
(Transverse, Longitudinal and Surface)?
• We classify them based on the directions of the particles in the medium compared to the direction
the wave or energy is going.
• Particles in a medium (like air) can move either up and down or back and forth. Waves are
classified according to the direction in which the particles in the medium move as a wave passes
by.
Transverse Waves
• A wave in which the particles of the medium move perpendicularly to the direction the wave is
travelling.
• Have crests (high points) and troughs (low points), Ex: seismic S-waves, vibrating guitar string
Longitudinal Waves
• Have parallel motion (waves are parallel to particle motion)
• Has compressions (crowded area) and rarefactions (stretched-out area)
• Ex: Sound waves, a spring, hitting the end of a slinky
Surface Wave
• Combination of both transverse and longitudinal waves
• Particles move both perpendicularly and parallel to the direction in which the wave travels
(particles move in circles/ellipses.
• Ex: ocean waves, swimming pool waves, seismic waves
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Seismic Waves
• P-Waves – fastest, longitudinal wave, can move through rock and liquids
• S-Waves – slower, transverse wave, can only travel through solids
• Surface Waves – lower frequency, responsible for most of the damage in earthquakes
• http://www.geo.mtu.edu/UPSeis/waves.html
Characteristics of Waves
• Key ideas:
o What are some ways to measure and compare waves?
o How can you calculate the speed of a wave?
o Why does the pitch of an ambulance siren change as the ambulance rushes past you?
Wave Properties
Amplitude: measures the amount of particle vibration or size of wave
• Greatest distance particles are displaced from their normal resting position
• In a transverse wave, the amplitude is the distance from the rest position to a crest or to a trough.
Wavelength: represented by the Greek letter lambda, (λ)
• Wavelength (λ) : the distance between any point on a wave to an identical point on the next wave,
measured in meters (m)
• Ex: In a transverse wave, the distance from one crest to the next crest, or one trough to the next
trough
• Ex: In a longitudinal wave, the distance between two compressions or two rarefactions
Amplitude and wavelength tell us about energy.
• The larger the amplitude of a wave, the more energy it carries.
• The shorter the wavelength of a wave, the more energy it carries.
Period: the time it takes for a complete cycle or wave oscillation to happen
• A time measurement….how long it takes for one full wavelength of a wave to pass a certain point.
• Symbol for period is T.
• Formula: T = 1/f (where f is the frequency)
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Frequency: the number of waves produced in a given amount of time
• Related to the period by the equation:
• Frequency = ___1___ OR f = ___1____
• period T
• Think about sitting in the ocean on an inner tube…if you wanted to count how many waves passed
you in one minute, you would be counting the frequency of the waves.
• Frequency is measured in Hertz (Hz). One cycle per second is 1 Hz. 5 cycles per second is 5Hz.
Wave Speed: How fast are the waves moving?
• There are two ways to find out.
o Wave speed = wavelength / period
v = λ / T
o Wave speed = frequency * wavelength
v = f * λ
Practice Problems:
• If a wave crest passes an inner tube every 2s, so the period is 2s, what is the frequency?
f = 1 / T, so f= 1/2s = .5 Hz
• The string of a piano that produces the note middle C vibrates with a frequency of 262Hz. If the
sound waves produced by this string have a wavelength in air of 1.30m, what is the speed of the
sound waves?
v = f * λ, so v= 262Hz*1.30m = 340.6 m/s
• A wave along a guitar string has a frequency of 440Hz and a wavelength of 1.5m. What is the
speed of the wave?
v = f * λ, so v= 440Hz * 1.5m = 660 m/s
The speed of a wave depends on the medium
Sound waves travel in air (about 340m/s –pretty fast)
Sound waves travel 3 – 4 times faster in water! This is how Dolphins communicate over long distances
Sound waves travel even faster in solids (15 – 20 times as fast in metal or rock)
Why do you think sound travels fastest in solids?
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o Kinetic molecular theory (how close or far molecules are from each other- the density of a
substance).
Properties of Sound
Sound waves are longitudinal waves caused by vibrations and carry energy through a medium
The speed of sound depends on the medium and the temperature of the medium
o Sound travels fastest in solids, then liquids, then gas (exception: rubber dampens vibrations –
used for soundproofing)
o Sound travels faster in a higher temperature medium – molecules are moving around faster
Loudness of Sound
How do sound waves change when you increase the volume on your TV?
o The intensity either increases or decreases
o Intensity depends on the amplitude of the sound wave and your distance from the source
o Intensity is measured in decibels (dB).
o The quietest sound a human can hear is 0dB. A sound at 120 dB is the threshold of pain—sounds
louder than this can hurt your ears and prolonged exposure can cause permanent deafness.
More Properties of Sound
Pitch: measure of how high or low a sound is and depends on the frequency of the wave
o High-pitch: made by something vibrating rapidly, like a violin string (high frequency)
o Low-pitch: made by something vibrating slowly, like a cello string (low frequency)
o Humans can hear sounds as slow as 20Hz up to 20,000 Hz. Any sound lower is infrasound and
any sound higher is ultrasound.
o Animals can hear frequencies outside the range of human hearing.
Musical Instruments
How do musical instruments work?
o Most instruments produce sound through vibration of strings (guitar), air columns (flute), or
membranes (drum)
o Example: A shorter length of string on a guitar vibrates more rapidly (higher frequency = higher
pitch)
o http://www.youtube.com/watch?v=qWhh_EqfBmk
How do we hear?
Your ear is made of three regions: outer, middle, and inner. Sound travels through your outer ear down the
ear canal, ending at the eardrum. Vibrations pass from the eardrum to 3 small bones of the middle ear
(hammer, the anvil and the stirrup). The stirrup strikes a membrane at the opening of the inner ear, which
sends waves through the spiral shaped cochlea. Hair cells near the basilar membrane in the cochlea,
stimulate nerve fibers that send an impulse to the brain. The brain interprets the impulse as sound!
The Doppler Effect
Imagine the last time you heard an ambulance. What changes as the ambulance gets farther away?
o Sound of the siren changes from a high-pitch (closer to you) to a low-pitch (farther from you)
o Pitch is determined by the frequency of sound waves
o Frequency changes when the source of waves is moving
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o The change in the observed frequency is known as the Doppler Effect
o http://www.youtube.com/watch?v=Kg9F5pN5tlI
Reflection and Refraction
Reflection: the bouncing back of a wave when it meets a surface or boundary
o Example: reflection of light waves can create a mirror image of a landscape when they hit the
surface of a lake
Refraction: the bending of waves when they pass from one medium to another
o Example: a spoon in a glass of water looks broken
Standing Waves
Pattern of vibration that simulates a wave standing still
Caused by interference of waves (the combination of two or more waves that results in a single wave
Electromagnetic Spectrum:
Consists of waves at all possible energies, frequencies and wavelengths.
o Each part of the electromagnetic spectrum has unique properties (different wavelengths and
frequencies – allows different waves to be used for different things.
o Frequency increases toward the right side (toward gamma rays) of the spectrum
o Wavelength increases toward the left side (toward radio waves) of the spectrum
o Which side has higher energy?
The right side (toward gamma rays) has higher energy; the energy of these
waves is proportional to the frequency.
1. Radio waves: longest waves, (from tenths of a meter to thousands of a meter;size of
buildings/humans), lowest frequencies.
Used in TV signals, AM/FM radio signals, and radar (air traffic control)
2. Microwaves: wavelengths in the range of centimeters. (size of butterflies)
Used to carry communication signals over long distances (space probes use microwaves
to transmit signals back to Earth)
Used in cooking
3. Infrared: slightly longer wavelengths than that of red visible light, size of a needle point
Infrared light from the sun warms you, heat lamps—keeps food warm, infrared sensor
can measure the heat energy that objects radiate, computers detect infrared signals from
external devices like a mouse.
4. Visible Light: colors that we can see, a very small part of the electromagnetic spectrum
All the colors that we can see being reflected, refracted or absorbed off other materials.
5. Ultraviolet Light: Invisible light that falls just beyond violet light (size of molecules)
Higher energy and shorter wavelengths than visible light
Many insects can see this light even though humans can’t
9% of the energy emitted by the sun, why you get a sunburn!
6. X-rays (size of atoms) and gamma rays (size of nuclei):
Very high energy, high frequency, very small wavelengths
X-rays used in medicine (X-ray image of bones)
Gamma rays used in medicine to treat cancer
Must be careful around both (with such high energy can kill normal cells and turn them
into cancer cells)
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Watch NASA: Tour of the EM Spectrum (can find online)
Unit 9: Electricity (didn’t get to this year)
Electricity: movement of electrons through a material
Conductor: a material in which electrons can flow easily under the influence of an electric field; has low
resistance
Good examples of conductors are metals; because electrons move freely in them
Insulator: used to prevent electric current from flowing in directions other than the desired direction;
have a high resistance to charge movement
Example: plastic coating around the copper wire of an electrical cord; keeps current from
escaping into the floor or into your body
Semi-Conductor: has properties between that of a conductor and insulator
Current (I): the rate at which the charges move through the wire. The unit for current is the ampere (A).
Voltage (V): the difference in charge between two points.
Formula: V = I * R, (Ohm’s Law), where I is current, and R is resistance
Resistance (R): a material’s tendency to resist the flow of charge (current).
Caused by internal friction, which slows the movement of charges through a conducting
material
Formula: resistance = voltage OR R = V/ I where I is the current
Current
This formula is commonly called Ohm’s Law, and the unit for Resistance is the ohm.
Practice problem: The headlights of a typical car are powered by a 12V battery. What is
the resistance of the headlights if they draw 3 A of current when they are turned on?
R = V/I so R= 12V / 3A = 4 ohms.
Power (Watts): rate at which energy is transferred or transformed