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?

J.Stevens, 2015 24

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

J.Stevens, 2015 26

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)

J.Stevens, 2015 27

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