science, matter, energy, and systems chapter 2 – part 1 scientific process

Science, Matter, Energy, and Systems

Chapter 2 – Part 1Scientific Process

Core Case Study: Carrying Out a Controlled Scientific Experiment

F. Herbert Bormann, Gene Likens, et al.: Hubbard Brook Experimental Forest in NH (U.S.)

Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site)

The Effects of Deforestation on the Loss of Water and Soil Nutrients

Built v-shaped dams across the creeks at the bottom of forested valleys

Measured amounts of water and dissolved plant nutrients


Investigators cut down all trees and shrubs in one valley

Sprayed area with herbicides to prevent regrowth


Amount of water flowing out of the deforested valley increased by 30-40%• Eroded soil• Removed 6x more

nutrients from soil Conclusions????

Scientists Use Reasoning, Imagination, and Creativity to Learn How Nature Works

Important scientific tools• Inductive reasoning – involves using

specific observations and measurements• Specific General

• Deductive reasoning – involves using logic to arrive at a specific conclusion based on a generalization or premise• General Specific

Inductive or Deductive?

All birds have feathers. Eagles are birds. Eagles have feathers.

A meatball falls to the ground when dropped from a height of 10 feet. An olive falls to the ground when dropped from a height of 2 feet. All objects fall to the Earth’s surface when dropped.

Deductive

Inductive

Nature of Science

An organized way of using evidence to learn about the natural world• Observations• Hypothesis• Experiment• Results• Conclusion• Repeating • Peer Review

Nature of Science

Hypothesis• Proposed scientific explanation

for a set of observations

A good hypothesis must: 1. Be testable.2. Be a statement, not a question.3. Predict cause and effect.

If…then…

Nature of Science

Null Hypothesis:• States that the variable will

have no effect on the outcome of the experiment

• Example: Light intensity has no effect on plant growth.

• Allows conclusions to be drawn that “reject” or “fail to reject” the null hypothesis

If…then…

Able toChange

Variable

Every experiment measures two • Independent variable -- the variable that

the experimenter controls.• answers the question "What do I

change/control?"

• Dependent variable -- the variable the experimenter measures (results). • answers the question "What do I

observe/measure?"

Scenario

A group of students is assigned a populations project in their APES class. They decide to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.

Independent Variable – What do I control ?

A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.

Dependent Variable – What do I measure?

A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.

Controlled Experiment

Experimental group - group that receives treatment in a controlled experiment.• Contains Independent Variable

Control group - group that does not receive treatment in a controlled experiment.• Does not contain Independent Variable

Experimental Group– Which group has the IV? A group of students is assigned a

populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.

Control – Which group doesn’t have the IV? A group of students is assigned a


Able toChange

Variable

Levels – measure of your independent variable• Example: • Number of seeds in a pot• Number of fish in a fish bowl• Number of times that an action is repeated

Levels – how is the IV measured? A group of students is assigned a


Controlled Experiment

Constant• What remains constant between

experimental groups Trials• Number of times you repeat an experiment• More tries = more reliable results

Sample size• The number of objects or events studied

Constants – What do I keep the same? A group of students is assigned a


Not all experiments are created equal…

Frontier science – preliminary testing

Reliable science – well supported and studied experiments• High probability of

being true Unreliable –

unsupported via peer review

Critical Thinking Questions:• Was the experiment

controlled?• Have the data been

verified?• Have the results been

reproduced by other scientists?

• Are the investigators unbiased?

• Have the conclusions been verified by impartial peer review?

Scientific Theories and Laws

Theory• Verified, credible

and widely accepted hypothesis

• Make future predictions

Law• Mathematical

description of what a theory explains

Paradigm Shift• Majority of

scientists in a field accept a new framework for theories and laws

Your Turn!

Case of the Ivory Billed Woodpecker http://www.pbs.org/wgbh/nova/nature/ivor

y-billed-woodpecker.html

http://www.pbs.org/wgbh/nova/nature/ivory-billed-woodpecker.html


The Case of the Ivory Billed Woodpecker

Case of the Ivory Billed Woodpecker http://www.pbs.org/wgbh/nova/nature/ivor

y-billed-woodpecker.html



The Case of the Ivory Billed Woodpecker

Wisconsin Fast Plants Laboratory Project

1. Make a list of questions you have about plants.• Be creative!

2. Suggested IV:• Fertilizer• Crowding• Acid (vinegar)• Soil• Glucose

Your Turn: Wisconsin Fast Plant Project!

1. On your paper include the following information:

1. Question 2. Hypothesis3. Null Hypothesis4. Experimental Design

1. Independent and Dependent Variable2. Control and Experimental Groups3. Levels4. Constants5. Sample Size

5. Detailed Procedure

Peer Review

Is the hypothesis testable, a statement, and does it predict a cause and effect relationship?

Will the data be quantitative rather than qualitative?

Are there any unaccounted for variables? If so, what are they?

Is the procedure logical? Any remaining questions or comments?


Chapter 2 – Part 2Chemical Bonding

MatterAny substance that: Occupies space Has mass Is made of atoms

Some Forms of Matter Are More Useful than Others

Matter quality – measure of how useful a form of matter is to humans as a resource• Based on

availability and concentration

Some Forms of Matter Are More Useful than Others

High-quality matter • highly concentrated• Near the Earth’s

surface• Great potential as a

resource

Low-quality matter• Not highly

concentrated• Located deep

underground or ocean

• Little potential for use

We Cannot Create or Destroy Matter

Matter consumption• Matter is converted

from one form to another

Law of conservation of matter – matter cannot be created nor destroyedEverything we think we have thrown away remains

here with us in some form…

Matter Consists of Elements and Compounds

Elements• Unique properties• Cannot be broken down chemically into

other substances• SPONCH

Compounds• Two or more different elements bonded

together in fixed proportions

Organic Compounds Are the Chemicals of Life

Inorganic compounds

Organic compounds• Macromolecules: complex organic

molecules• Carbohydrates• Proteins• Nucleic acids• Lipids

Atomic Composition

No unique substances in living things, just different amounts

“Same ingredients, different recipes.”

http://education.jlab.org/beamsactivity/6thgrade/tableofelements/index.html

Example: Carbon

• Atomic Number = 6

• 6 Protons

• 6 Electrons

• Atomic Mass = 12

• 12 – 6 = 6

• 6 Neutrons

Your Turn!

Atomic Mass #...

ELECTRONEGATIVITY

The tendency of an atom to attract electrons to itself when it is bonded to another atom

Increase

Incre

ase

http://education.jlab.org/beamsactivity/6thgrade/tableofelements/index.html

BONDING OPTIONSCOVALENT BOND By sharing electrons

(small difference in EN)

IONIC BOND By transferring electrons (producing ions)

(big difference in EN)

Chemical Bonding

Atoms combine according to certain rules

• Rules determined by the number of electrons found in the outermost energy level

• First energy level = 2 electrons• Second energy level = 8 electrons• Third energy level = 8 electrons

Chemical Bonding

Covalent Bonds

Sharing of electrons• Electrons travel in

the orbitals of both atoms

Each atom fills out the outermost energy level

Water: A Covalent Bond

Ionic Bonds

Transfer of electrons

Ex. NaCl• Sodium has one

electron in outer shell Na +

• Chlorine has seven electrons in its outer shell Cl –

Ionic Bond

Ion = charged particle• Anion = negatively charged• Cation = positively charged

Strong attraction between oppositely charged ions forms the ionic bond

Ionic Bond

Trick to Remember! If an atom GAINS electrons,

its overall charge becomes more negative.

If it LOSES electrons, its charge becomes more positive

Your Turn!

Bonding Practice Covalent: Carbon and Chlorine Ionic: Sodium and Chlorine


Chapter 2 – Part 3Water

Why is it important?

Covers ¾ of Earth’s surface!• Most abundant compound in most

living things Exceptional substance with many

extraordinary qualities!

Unusual Properties Determine characteristics of:

Atmosphere

Ocean

Land

Water’s Structure…Simple?

Hydrogen• 1 electron…needs 2

Oxygen• 6 electrons (outer

shell)…needs 8 Covalent Bonding

Polar Molecule

Charges are unevenly distributed• Partial positive• Partial negative

Electronegativites of atoms differ

Electronegativity

Ele

ctro

neg

ativ

ity

Hydrogen Bonds

Attraction between two different molecules

“weak” bond Not “real” bond b/c

no sharing or transferring of electrons • Ex: water, proteins, &

DNA

How many hydrogen bonds can each water molecule form?

As one hydrogen bond is broken another one forms

Each bond lasts trillionths of a second

Substantial percentage bonded to neighbor

Cohesion

Attraction between molecules of the same substance

Causes molecules on the surface of water to be drawn inward• Why water forms

beads on smooth surfaces

• Why insects can walk on water

Surface Tension

Result of cohesion How it “stretches or

resists breaking” Water molecules form

weak elastic membrane• Water to water • Water to air

Adhesion

Attraction between molecules of different substances• Meniscus

Water to Water

Water to Glass

Capillary Action

Forces that draw water out of the roots of a plant and up into its stems and leaves

Holds column of water together as it rises

Cohesion and adhesion

Density

Less dense as a solid Hydrogen bonds stay

connected• less energy in system

so bonds don’t break More space occurs

between water molecules

Solutions

All components are evenly distributed throughout• Solute – substance that

is dissolved• Solvent – the substance

in which the solute dissolves

Due to water’s polarity• Can dissolve ionic

compounds and other polar molecules

Solubility

Water surrounds the charged ends and separates the molecules

Suspensions

Mixtures of water and nondissolved material• Materials don’t

dissolve but separate into pieces so small that they do not settle out

Example• Blood

Your Turn!

Water Property Lab


Chapter 2 – Part 4Isotopes and Nuclear

Reactions

Isotopes

Number of neutrons can vary from one atom of an element to another• Changes atomic mass, not atomic

number Atomic number NEVER changes

Isotopes

H = hydrogen1

1

H = deuterium

H = tritium

1

2

1

3

Identified by mass #

Isotopes

Isotopes have SAME number of protons but DIFFERENT numbers of neutrons• Heavier• Behave identical in chemical reactions

Same # electrons = same chemical properties

Radioactive Isotopes

Diagnose and treat diseases• Cardiovascular

disease• Cancer radiation

Sterilize foods• Kill bacteria • Preserve food

Measure the ages of certain rocks• Fossils

Matter Undergoes Physical, Chemical, and Nuclear Changes

Nuclear change – changes in the nuclei of atoms• Nuclear fission –

nucleus splits and releases neutrons plus energy

Matter Undergoes Physical, Chemical, and Nuclear Changes

Nuclear change – changes in the nuclei of atoms• Nuclear fission –

nucleus splits and releases neutrons plus energy

• Nuclear fusion – two nuclei fuse together and release energy

Nuclear Power 6:51

Light-Water-Moderated and -Cooled Nuclear Power Plant with Water Reactor

After 3 or 4 Years in a Reactor, Spent Fuel Rods Are Removed and Stored in Water


Chapter 2 – Part 5pH

What do vinegar, lemons, and orange juice have in common?

Characteristics of Acids

Taste Sour React with metals Often produce

hydrogen gas Can burn your skin

What do milk, Comet, and Tums have in common?

Characteristics of Bases

Taste Bitter Feel Slippery Neutralize Acids• Antacids

Dissolve grease

But, what exactly are acids and

bases?

Substance that ionizes in water to give hydrogen ions (H+)

Acid

Examples of Acids

HCl H2SO4

HNO3

HF Juices

Substance that ionizes in water to give hydroxide ions (OH-)

Base

Examples of Bases

NaOH Ca(OH)2

KOH Soap, Ammonia,

Baking Soda

The pH Scale

Measurement system that indicates the concentration of H+ ions in solution.• The pH scale ranges from 0 to

14.

The pH Scale

pH = “power of hydrogen”• Each step increases by a power

of ten

pH Scale

pH Calculations

Remember: For every one-increment change in pH, the ions change by a factor of 10.

Example: What is the difference in H+ concentration between pH 6 and pH 4?• pH 6 – pH 4 = pH 2• H+ is 100 times more concentrated in the

pH 4 solution

pH Calculations

Remember: Concentration of H+ and OH- always equals 10-14 M or pH 14

Example: [H+] = 10-6 M• pH is 6: weak acid• [OH-] = 10-8 M

pH and Water

Why does water have a pH of 7?• Hydronium ions = hydroxide ions • (H+) = (OH-)

H20 H+ + OH-

Interesting fact…

Water can act as an acid or a base!!!

Interesting fact…

Amphoteric -substance that can act as either an acid or a base.

Your Turn!

Review of pH Calculations

pH Scale

Your Turn…pH of natural substances

Substances:• Soil• Freshwater• Saltwater• Rainwater

Tools:• Soil – capsules• Water (use 2 of the following) - pH meter,

litmus paper, or microkit

Your Turn…pH of natural substances

Capsules

pH Meter Litmus Paper

Microkit

Soil

Freshwater

Saltwater

Rainwater

Buffers

Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.

Buffers are working

while you exercise!

Ocean pH

Surface water pH ranges from 8.0 to 8.3• Average 8.1

Ocean water combines with CO2

Forms weak Carbonic Acid

H20 + CO2 H2CO3 H+ + HCO3-

Ocean pH

Average pH 8.1• BASIC?

Carbonic Acid?

Why is the ocean pH slightly basic when CO2 (an acid) is

added?

Carbonate Buffering

Keeps ocean pH about same (8.1) pH too high, carbonic acid releases H+

pH too low, bicarbonate combines with H+

H2CO3 H+ + HCO3-

HCO3- + H+ H2CO3

Carbonate Buffering

Marine organisms die and sink into deep ocean• Calcium carbonate in shell neutralizes acid

through buffering

CaCO3 CO3- + H+

HCO3- + H+ H2CO3

Carbonate Buffering

Dead mollusks are the antacids of the sea!

Carbonate buffering

Recent Decrease in Ocean Acidity

Excess carbon dioxide in atmosphere• 33% CO2 released by burning fossil fuels

ends up in ocean Overwhelming oceans natural ability to

buffer itself• pH has decreased 0.1 since preindustrial

times

Recent Decrease in Ocean Acidity

More difficult for certain marine creatures to build hard parts out of calcium carbonate• Plankton• Corals

Alter food chain of ocean!


Chapter 2 – Part 6Thermodynamics

Energy Comes in Many Forms

Kinetic energy - energy of motion• Mass and velocity!• Electromagnetic

radiation of waves• Short = greater

energy

Kinetic energy

Atoms and molecules in any gas, liquid, or solid are always in motion

• Vibrate around average position

Kinetic Energy = ½ (mass)(velocity)2

Temperature

Measure of the average kinetic energy of the atoms and molecules in the substance

Measured in degrees• Celsius• Fahrenheit• Kelvin

Heat

Measure of total kinetic energy of the atoms and molecules in a substance

Measured in calories

Calorie

Amount of heat needed to raise the temperature of 1g of water by 1oC

1 food Calorie (1 kilocalorie) = 1000 calories

What’s the difference?

Which has greater average Kinetic Energy?• Higher Temperature?

Which has greater total Kinetic Energy?• More Heat?

Energy Comes in Many Forms

Potential energy - energy of position• Stored energy; can

be changed into kinetic energy

• Examples: rock held in hand, unlit match, gasoline

Some Types of Energy Are More Useful Than Others

Energy quality - measure of an energy source’s capacity to do useful work

High-quality energy – concentrated energy that has a high capacity to do useful work• High-temperature heat• Concentrated sunlight• High velocity wind

Some Types of Energy Are More Useful Than Others

Energy quality - measure of an energy source’s capacity to do useful work

Low-quality energy – energy that is dispersed and has little capacity to do useful work• Low temperatures

Energy Changes Are Governed by Two Scientific Laws

First Law of Thermodynamics• Energy input always equals energy output

Second Law of Thermodynamics• Energy always goes from a more useful to a

less useful form when it changes from one form to another• Decreased energy efficiency

Life application

94% of the money you spend for gasoline is not used to transport you anywhere!

The Second Law of Thermodynamics in Living Systems

Your Turn!

Potential vs. Kinetic worksheet


Chapter 2 – Part 7Systems

Systems Have Inputs, Flows, and Outputs

System – set of components that function and interact in some regular way• Inputs from the

environment• Flows,

throughputs• Outputs

Systems Respond to Change through Feedback Loops

Positive feedback loop - causes a system to change in the same direction

Systems Respond to Change through Feedback Loops

Negative feedback loop – causes a system to change in the opposite direction from which it is moving• Opposing process

Can promote sustainability!• Aluminum mining

can recycling

Video Clip – Planet Earth Forests

Cicada Life Cycle

21:00-26:00

Time Delays Can Allow a System to Reach a Tipping Point

Time delays vary• Between the input

of a feedback stimulus and the response to it

• Example: Planting trees

Tipping point, threshold level• Causes a shift in

the behavior of a system

System Effects Can Be Amplified through Synergy

Synergistic interaction – two or more processes interact so that the combine effect is greater than the sum of their separate effects• Helpful• E.g., campaign vs. individual persuasion

• Harmful• E.g., Smoking and inhaling asbestos

particles

science, matter, energy, and systems chapter 2 – part 1 scientific process

Documents

loss of water

soil nutrientsamount

radish plant height

independent variable

effect of sunlight

radish plants

effects of deforestation

soil nutrientsinvestigators