Physical Science Mid-Term Review 2015 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.

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

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

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:

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.

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

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.

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

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

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

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.

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)

****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!!!!)

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)