Science Review: Method, Matter, Energy & Systems

Chapter 3

Scientific Method: 1. Observation

2. Problem or Question

3. Research (lit review)

4. Hypothesis

5. Experimentation

6. Analyze Data

7. Conclusions

8. Publish

https://www.youtube.com/watch?v=BRDApYgvDqQ

LAB SAFETY

1. Observation

• Observe a phenomenon of interest

• Observations stem from

– First hand experience

– Examination of literature

– Discussion with other scientists

• Example: Eating chicken soup seems to cure the common cold

2. Question

Question: why? how? about observation – What characteristic

of chicken soup makes it seem to cure a cold?

Hypothesis: possible explanation of observation or answer to question

= A predication about the relationships between the Independent and Dependent variables

– If the soup temperature is decreased, then the cold will not be “cured”

3. Research & 4. Hypothesis

Variables

Independent variable (IV) Manipulated variable

• It’s what you’re testing • The effect of ____IV_______....

Hypothesis: The heat from the soup “cures” the cold. What is

the Independent variable? • Temperature of chicken soup

Levels of the Independent variable: specific groups or categories chosen by the experimenter Hypothesis: The heat from the soup “cures” the cold.

IV = Temperature of chicken soup Levels of IV = cold, warm hot; 50°, 75°, 90°

Dependent variable (DV) Responding variable

• It’s what you observe/measure • Affected by the IV

Hypothesis: The heat from the soup “cures” the cold. What is the Dependent variable?

• Curing the cold/ “patient condition”

5. Experimentation

Tests the hypothesis by collecting data

• Constant: aspects of experiment that are kept same for entire experiment/ all groups

• Example: Brand of chicken soup • Other examples?

• Why have constants?

– So you know that the changes in the Dependent Variable (YOUR RESULTS), are only due to the Independent Variable (YOUR MANIPULATION) and not some other factor

6. Data Analysis & Presentation

Tables: ▫ Used during experiment for

raw data

▫ Or, summarizes raw data into averages and statistics for final presentation

Trial1 Trial 2 Trial 3 Average

Dime

Penny

Nickel

Quarter

Table 1. How many drops of water can fit on a coin?

Graphs

• Independent variable (IV) goes on X-axis

• Dependent variable (DV) goes on Y-axis

• Graphs always have: – Name and number (Figure 1)

– Title caption (following Figure number)

– Axis labels with units

– Increments along graph must be proportional Y axis

X axis

Two main types of graphs: Line graphs: show relationship over time generally Bar graphs: compare IV and DV

Graph Example

0

20

40

60

80

100

120

140

160

1 2 3 4 5

Month

Am

ou

nt

of

rain

fall

(cm

)

Site 1

Site 2

Site 3

Figure 1. Amount of Rainfall (cm) at 3 Sites

Graph Example

0

10

20

30

40

50

60

Feeder 1 Feeder 2 Feeder 3

Perc

en

t seed

typ

e e

ate

n

A

B

C

Figure 2. Percent eaten of seed types A, B, C at 3 bird feeders

7.Conclusions & 8. Publish

• When you interpret & discuss results – What does your data indicate?

– Do you accept or reject the hypothesis?

– How does it compare with past, related research

• Repeat & expand experiments

• Communicate results by publishing scientific articles in journals

Hypothesis, Theory, or Law

Hypothesis: unconfirmed explanation of observed phenomenon that can be tested by further research. (ex: use of stem cells can cure spinal cord injuries)

Theory: hypothesis verified in so many experiments it is believed to be true by experts. (Theory of Evolution, Big Bang Theory)

“Best & most reliable knowledge we have about how nature works”

Law: Theories continuously supported over decades. Laws of science can’t be broken; happen same way every time. (Laws of Thermodynamics; Kepler’s Law of Planetary Motion; Newton’s Laws, etc.)

Math Review – What you should already know, but just in case…

• Scientific Notation – Serves to make really big or small

numbers easier to read & say

– Uses exponents of 10

• Examples: – 2,000 = 2.0 x 103

– 0.00056 = 5.6 x 10-4

– 3,000,000,000 = 3 billion = 3.0 x 109

– 7 = 7.0 x 100

https://www.youtube.com/watch?v=AWof6knvQwE

Math Review

• Working with Scientific Notation

– When adding or subtracting:

• Put in same exponent, then add/subtract numbers (exponent stays same)

• Example: (1.9 x 10 -3) – (1.5 x 10 -4 ) = (19 x 10-4) - (1.5 x 10 -4 ) = 17.5 x 10 -4 = 1.75 x 10-3

Math Review • Working with Scientific Notation

– When multiplying numbers: • Multiply numbers • Add exponents • Example, (3.1 x 105) (4.5 x 105) =13.95 x 1010 or 1.4 x

1011

– When dividing numbers: • Divide numbers • Subtract exponents

• Example: 9 x 10 5 = 3 x 10 2

3 x 10 3

• International System of Units (SI) aka Metric System

– Basic or Base Units:

• Meter (m) = basic unit of length (height, width, diameter)

• Gram (g) = basic unit of weight

• Liter (L) = basic unit of volume; amount of liquid or gas

Math Review

• Units – Area and Volume

– Area – m2, cm2, mm2, etc

– Volume – ml, l, cm3, m3, mm3

– Volume Conversions

• 1 ml = 1 cm3

• 1 l = 1000 ml

Math Review

Giga (G) (109)

Mega (M) (106)

King: Kilo (k) (103)

Henry: Hecto (h) (102)

Died: Deka (da) (101)

By: base metric unit (100), i.e. g, l, or m

Drinking: Deci (d) (10-1)

Chocolate: Centi (c) (10-2)

Milk: Milli (m) (10-3)

Micro (µ) (10-6)

Nano (n) (10-9)

Metric System

Based on Multiples of 10

•To convert among units: MOVE DECIMAL POINT LEFT or RIGHT

When describing the concentration of something in water or soil

ppm parts per million 1 mg/L of water or 1mg/kg

ppb parts per billion 1µg/L of water or 1µg/Kg

Important Features of the Scientific Process:

Skepticism: reserve doubt for anything unconfirmed or unverified

Reproducibility: Data/results must be able to be reproduced by others. Once is never enough!!

Peer Review: Send off methods, results, and conclusions to other experts in that field. They review and respond. Then can publish in scientific journals.

• Science has limitations – Hypotheses & theories have high probability of

being true while not being absolute. Nothing is “proven” – always some uncertainty

– Environmental phenomena involve many interacting variables and complex interactions

– Statistical methods are used to estimate very large or very small numbers

– Scientific process is limited to the natural world (not ethical, philosophical or religious debate)

Sound Science

Consensus science: widely accepted by experts.. also called sound science.

Multiple peer review leads to sound science – any flaws are found and theories are modified in the “frontier science” stage.

• Junk Science

Results or hypotheses that are portrayed as sound science, but are not well tested or peer reviewed

Loved by the media and politicians

http://www.dhmo.org/

Systems and Models

System: set of components that interact in a regular or predictable way

3 key components: Inputs (from the environment), output

Feedback Loops

Feedback loop: When output is fed back into system as an input and leads to changes in that system

Positive feedback loop: causes a change in same direction Examples:

Oxytocin & contractions

Feedback Loops

Negative feedback loop: causes a change in the opposite direction

Examples:

body temperature

& sweating

Recycling cans

Feedback Loops

Time delay: amount of time between input and response to it. If too long, a system may cross the tipping point & no longer be able to be repaired

Tipping point (Threshold level): the point at which a fundamental shift in the behavior of a system occurs

CLIMATE CHANGE!

Science

Systems and Models Synergistic interaction/ Synergy: two or

more processes interact and the combined effect is greater than the sum of their separate effects

Example: Two people can each lift 100 pounds. Working together they can lift 275 pounds (not 200)

Systems are too complex to fully predict all outcomes of any given action

Butterfly Effect: you can never change just one thing (Chaos Theory)

Important elements in APES: hydrogen (H), carbon (C), oxygen (O), nitrogen (N), phosphorous (P), sulfur (S), chlorine (Cl), fluorine (F), bromine (Br), sodium (Na), calcium (Ca), lead (Pb), mercury (Hg), arsenic (As), and uranium (U)

Important molecules & compounds in APES: O2, N2, Cl2, nitric oxide (NO), carbon monoxide (CO), hydrogen chloride (HCl), H2O, nitrogen dioxide (NO2), carbon dioxide (CO2), sulfur dioxide (SO2), ozone (O3), methane (CH4), hydrogen sulfide (H2S), calcium carbonate (CaCO3), sulfuric acid (H2SO4), nitric acid (HNO3), glucose (C6H12O6)

CHEMISTRY REVIEW!

pH: concentration of

Hydrogen (H+) or Hydroxide (OH-) ions in solution

▫ Neutral = 7

▫ Acids: more H+ than OH-; ph < 7

▫ Bases: more OH- than H+; ph > 7

• Matter Quality: how useful a form of matter is to us as a resource

High quality matter: useful, concentrated, near

surface of Earth, high potential for resource

Low quality matter: dilute, hard to find, low

potential

Example: aluminum ore is low quality

while recycled aluminum cans is high quality

Example: solid salt in a salt mine is high

quality while the salt in the ocean is low quality

Law of Conservation of Matter: You cannot create nor

destroy matter, it can only be changed

Nuclear change: change in nuclei of its atoms

Half-life: how long it takes for one half of the amount of material to turn into a different isotope (or time to reduce by ½)

*IMPORTANT: Dangerous radioactive materials take 10 half lives to become safe

Half-life Examples:

Plutonium-239 has a half life of 24,000 years. How long must it be stored before it will be at a safe level?

10 half lives x 24,000 years = 240,000 yrs

Iodine-131 has a half life of 8 days. After 4 half-lives, what fraction of the sample is still radioactive?

1/2^4 = 1/16

List the fraction amounts for each half-life up to 10 half lives

1 – 1/2, 2 – 1/4, 3 – 1/8, 4 – 1/16, 5 – 1/32, 6 – 1/64,

7 – 1/128, 8 – 1/256, 9 – 1/512, 10 – 1/1024…

• Nuclear Fission: when large, unstable nucleus is split apart into lighter nuclei releases energy and neutrons.

• The neutrons will make other unstable nuclei split. This is a chain reaction.

Conventionally use Uranium in U.S. power plants

• Nuclear Fusion: when two light elements, like hydrogen, are forced together at extremely high temps until they fuse to form a heavier nucleus release tons of energy

Stars use this; you get A LOT more power from fusion than fission

Hydrogen bomb: combination of hydrogen into helium

D-T fusion is deuterium (H-2) with tritium (H-3) to make Helium and one neutron (used in thermonuclear weapons)

Hydrogen-3

(tritium nucleus)

100

million °C

Reaction

conditions

Energy

Products

Neutron

Nuclear fusion

Fuel

Hydrogen-2

(deuterium nucleus)

Helium-4 nucleus Proton

Energy Quality: measure of the capacity

of a type of energy to do useful work

High quality energy: great capacity to do useful work b/c it’s concentrated Example: high-temp heat, concentrated sunlight,

high-speed wind, burning fossil fuels

Low quality energy: too dispersed to do useful work

• First Law of Thermodynamics/ Law of Conservation of Energy

Energy cannot be created or destroyed but can be transformed (changed from one form to another)

• Second Law of Thermodynamics

When energy changes form, some useful energy is always degraded into lower quality, less useful energy.

Heat radiated into environment

▫ Driving a car: 20-25% of chemical energy in fuel is converted to mechanical and electrical energy; rest is lost as heat

▫ Energy is lost as go up food chain through heat