The Nature The Nature of Scienceof Science

Class NotesClass Notes

The Scientific The Scientific MethodMethod

What is Science?What is Science?

““ScienceScience” derived from Latin ‘to know’” derived from Latin ‘to know’

Way of asking and answering questions Way of asking and answering questions about the world around usabout the world around us

Can only address questions that are Can only address questions that are testabletestable

Scientific thinking reduces personal, Scientific thinking reduces personal, emotional reactionsemotional reactions

Scientific DesignScientific Design

Scientific method Scientific method – common steps that – common steps that scientists use to gather information and scientists use to gather information and answer questionsanswer questions

There is no ONE scientific method.There is no ONE scientific method. This is just a general outline to follow.This is just a general outline to follow.

Step 1: Observe and Ask Step 1: Observe and Ask a Questiona Question

An An observationobservation is made about the natural world. is made about the natural world. Songbirds seems to be absent in the forests of Guam.Songbirds seems to be absent in the forests of Guam. This observation was made around the same time This observation was made around the same time

that brown tree snakes were first spotted in Guam.that brown tree snakes were first spotted in Guam.

The scientist will then develop a general question The scientist will then develop a general question that they are setting out to answer.that they are setting out to answer. Example: Is there a relationship between the lack of Example: Is there a relationship between the lack of

songbirds in the forests in Guam and the introduction songbirds in the forests in Guam and the introduction of the brown tree snake?of the brown tree snake?

Step 2: Create a Step 2: Create a HypothesisHypothesis

HypothesisHypothesis – a possible explanation for a – a possible explanation for a question or problem that is testable and question or problem that is testable and based on previous knowledgebased on previous knowledge It is NOT an “educated guess”It is NOT an “educated guess” Example: Example: If If there are brown tree snakes, there are brown tree snakes, thenthen

they must eat the song birds.they must eat the song birds.

Step 3: Carry Out a Step 3: Carry Out a Controlled ExperimentControlled Experiment

Controlled experiment Controlled experiment – an investigation that – an investigation that tests a hypothesis by the process of collecting tests a hypothesis by the process of collecting information under controlled conditionsinformation under controlled conditions

Made up of:Made up of: Independent variableIndependent variable Dependent variableDependent variable Control groupControl group Experimental groupExperimental group ControlsControls

Experimental DesignExperimental Design

Independent (manipulated) variableIndependent (manipulated) variable: condition or : condition or event under study event under study

Dependent (responding) variableDependent (responding) variable: condition that : condition that could change under the influence of the could change under the influence of the independent variable (measure this)independent variable (measure this)

Controls (controlled variables)Controls (controlled variables): : conditions which conditions which could effect the outcome of the experiment so could effect the outcome of the experiment so they must be held constant between groupsthey must be held constant between groups

Experimental DesignExperimental Design

Experimental groupExperimental group: group(s) subjected to : group(s) subjected to the independent variablethe independent variable

Control groupControl group: group kept “normal”, used as : group kept “normal”, used as measuring stickmeasuring stick

Step 4: Analyze Data and Step 4: Analyze Data and Draw ConclusionsDraw Conclusions

DataData – information obtained from investigations – information obtained from investigations

Qualitative dataQualitative data: observational data: observational data Example: color changes, descriptionsExample: color changes, descriptions

Quantitative dataQuantitative data: numerical (numbers) data: numerical (numbers) data Example: time, quantities, measurementsExample: time, quantities, measurements

Examine the data for patterns and trends and Examine the data for patterns and trends and make conclusions from the data that you make conclusions from the data that you collected.collected.

Step 5: Publishing Step 5: Publishing ResultsResults

Scientists then publish and share their data Scientists then publish and share their data through scientific journals so that other through scientific journals so that other scientists can review and use this scientists can review and use this information.information.

Science is collaborative and results must be Science is collaborative and results must be reproduced and verified in order to be reproduced and verified in order to be commonly accepted.commonly accepted.

Theories and Natural Theories and Natural LawsLaws

TheoryTheory: a description of the world that : a description of the world that covers a relatively large number of covers a relatively large number of phenomena and has met many phenomena and has met many observational and experimental testsobservational and experimental tests

Law of NatureLaw of Nature: theory (or group of : theory (or group of theories) that has been tested extensively theories) that has been tested extensively and seems to apply everywhere in the and seems to apply everywhere in the universeuniverse

ExampleExample

Observation: Dogs that wear the red collar Observation: Dogs that wear the red collar seem to have less fleas.seem to have less fleas.

Hypothesis: If dogs wear a red collars, then Hypothesis: If dogs wear a red collars, then they will have less fleas than dogs that they will have less fleas than dogs that wear other color collars.wear other color collars.

Experimental DesignExperimental Design

Obtain 500 dogs of various breeds from Obtain 500 dogs of various breeds from local shelters. local shelters.

Randomly assign individuals to 2 groups.Randomly assign individuals to 2 groups. What would you do to the experimental What would you do to the experimental

group?group? What would you do to the control group?What would you do to the control group?

Board the dogs in identical environments Board the dogs in identical environments and treat them the same and treat them the same exceptexcept for the for the independent variable.independent variable. What is the independent variable?What is the independent variable?

After 2 weeks the dogs are examined.After 2 weeks the dogs are examined. What is the dependent variable? What are we What is the dependent variable? What are we

measuring?measuring?

Results: Results:

The dogs wearing the red collars were The dogs wearing the red collars were virtually free of fleas after the 2 week virtually free of fleas after the 2 week period.period.

The dogs without the collars had about the The dogs without the collars had about the same number of fleas as when the same number of fleas as when the experiment began.experiment began.

What can we conclude??What can we conclude??

Scientific Measurement

The metric system• Decimal based system - scaled on multiples of 10• AKA the International System of Units, or SI• Two ways to solve conversion problems:

– Ladder method– Dimensional Analysis

Kilo (k) 1/1000=0.001

Hecto (h) 1/100=0.01

Deka (da) 1/10=0.1

Meter (m) /liter (L) /gram (g)

1

Deci (d) 10

Centi (c) 100

Milli (m) 1000

KILO1000Units

HECTO100

Units

DEKA10

UnitsDECI

0.1Unit

CENTI0.01Unit

MILLI0.001Unit

MetersLitersGrams

Metric Conversions - Ladder Method

How do you use the “ladder” method?

1st – Determine your starting point.

2nd – Count the “jumps” to your ending point.

3rd – Move the decimal the same number of jumps in the same direction.

4 km = _________ m

12

3

How many jumps does it take?

Starting Point Ending Point

4.1

__.2

__.3

__. = 4000 m

Metric Conversions - Dimensional Analysis

Question: 8400mg = ___?___g

Steps:

1. Know the conversion factor (there are 1000mg in 1g).

2. Set up a multiplication problem and cancel out units on the top and bottom of the fractions.

3. Do the math to find the answer (8.4g).

1 liter = 1000 cubic centimeters

1 Liter

1 milliliter (mL)

Everything you ever wanted to know about the Metric System.

Graphing

• Graph- pictoral representation of the information recorded in a data table.

• Two common types:– Line graph– Bar graph

Line Graph

• Shows relationship between two variables.

Bar Graph

• Used only to show comparisons.

Graphs must have…

• A title

• Labeled X and Y axes

• Units on X and Y axes

• Legends

Practice making a line graphTable 1: Breathing rate of fish

Temp (deg C)

Rate (per min)

10 15

15 25

18 30

20 38

23 60

25 57

27 25

Practice making a bar graphTable 2: Average rainfall

Month

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

Rainfall (mL)

15 21 28 24 16 8 2 1 2 3 5 10

Science Lab Safety

Lab Safety Video:http://www.flinnsci.com/teacher-resources/teacher-resource-videos/best-practices-for-teaching-chemistry/safety/laboratory-safety-challenge/

Safety Symbols

Flame

Poison

Dangerous Fumes

Wear Safety Goggles

Electrical Shock

Safety Rule #1

Never perform any unauthorized experiments or use any equipment or instruments without proper instruction.

Always follow all directions given by your teacher!

Safety Rule #2

Do not begin working on your lab unless your teacher is present!

Safety Rule #3

When required, proper eye protection must be worn during the entire class period!

Safety Rule #4

When something breaks or spills, you must notify your teacher so it can be cleaned up properly.

DO NOT TRY TO DO THIS YOURSELF!

Safety Rule #5

When working on a lab, dangling jewelry should be removed and long hair should be tied back.

Safety Rule #6

Do not eat or drink anything in the lab at any time.

Safety Rule #7

Consider every material used in the lab as dangerous.

Avoid inhaling fumes, tasting, touching, or smelling any chemical unless your teacher instructs you otherwise.

Rinse anything that spills on your skin with water immediately.

Safety Rule #8

Nothing is to be taken from the laboratory unless checked out to you in writing by your teacher.

Safety Rule #9

Never become involved in horseplay or practical jokes in the lab.

Use maturity at all times when working in the lab.

Safety Rule #10

Never point a test tube toward yourself or anyone else.

Safety Rule #11

Do not put anything in the sink or garbage can unless instructed by your teacher.

Always clean up according to the lab and teacher’s instructions.

Safety Rule #12

Note the location of the safety equipment in and around the classroom.

Always wash your hands with soap and water before leaving the lab.

Characteristics of Living Things

Characteristics of Life

All living things are made of cells A cell is the smallest unit of life and gives all

organisms an orderly structure

Organisms can be made of one cell (unicellular)

Example bacteria, amoeba, paramecia

Or, organisms can be made of many cells (multicellular)

Examples plants, animals, fungi

All organisms reproduce

All organisms must produce offspring in order to continue the species

Individual organisms do not need to reproduce to survive, but they must reproduce for the species to survive.

Species – a group of organisms that can interbreed and produce fertile offspring.

All organisms grow and develop.

Every organism’s life begins as a single cell.Some organisms will remain a single cell

that just gets larger.Other organisms will become many cells

that grow and develop.

Growth – An increase in the amount of living material

Development – All of the changes that take place during the life of an organism

All living things maintain homeostasis.Homeostasis – regulation of an

organism’s internal environment to maintain conditions suitable for its survival

Example: The temperature of your body gets too high so you sweat to lower the temperature.

All living things use energy.The cells of an organism are always hard at

work.

Just to read this sentence cells in your eyes and brain are working. At the same time cells are digesting your last meal, while blood cells are moving chemicals in your body, and other cells are repairing damage to your body. The list goes on and on…

All organisms respond to their environment.

Stimulus and responseStimulus anything in the organism’s

external or internal environment that causes an organism to react

Response a reaction to a stimulus

Example: The leaves of a plant will grow towards the light.Stimulus lightResponse growth towards the light

All living things have a metabolism

Metabolism – All of the chemical reactions that occur in an organism

The cells of living things are made of chemicals that allow an organism to survive.

Electron Microscopes• Used to observe VERY small objects that require

going beyond the limit of resolution of a compound light microscope. – Transmission electron microscopes (TEMs)-shine

beam of electrons at sample and magnify the image.

– Scanning electron microscopes (SEMs)-beam of electrons scan across surface of object; electrons that bounce off specimen are detected to generate the image.

MitochondriaCapillary

Plant cellTEM images

Hypodermic Needle Velcro

Bedbug

Cobweb

Red blood cells

SEM images

Compound Light Microscopes• Frequently used tools of biologists.• Magnify organisms too small to be seen

with the unaided eye.• To use:

– Sandwich specimen between transparent slide and thin, transparent coverslip.

– Shine light through specimen into lenses of microscope.

• Lens closest to object is objective lens.• Lens closest to your eye is the ocular lens.

• The image viewed through a compound light microscope is formed by the projection of light through a mounted specimen on a slide.

How does a compound light microscope work?

• Video tutorial

Always carry a microscope with one hand holding the arm and one hand under the base.

Body Tube

NosepieceObjectives or Objective Lenses

Stage Clips

Light Source

Eyepiece/

Ocular Lens

Arm

Stage

Coarse Adjustment

Fine Adjustment

Always carry a microscope with one hand holding the arm and one hand under the base.

Base

Diaphragm

Magnification

• The process of enlarging something in appearance, not actual physical size.

What’s my power?

To calculate the power of magnification or total magnification, multiply the power of the ocular lens by the power of the objective.

Power of Ocular lens X power of Objective 10 X 40 = 400

Comparing Powers of Magnification

We can see better details with higher the powers of magnification, but we cannot see as much of the image.

Which of these images would be viewed at a

higher power of magnification?

Resolution

• The shortest distance between two points on a specimen that can still be distinguished as two points.

Limit of resolution

• As magnifying power increases, we see more detail.

• The point where we can see no more detail is the limit of resolution.– Beyond the limit of resolution, objects get

blurry and detail is lost.– Use electron microscopes to reveal detail

beyond the limit of resolution of a compound light microscope!

Field of view

• The diameter of the circle of view when you look down the microscope.

What happens to the size of the field of view as you increase magnification?

Proper focusing technique

1. Check that the light is on.2. Add the slide3. Check the objective lens.- low power!4. Raise the stage.5. Look through the eyepiece & FOCUS DOWN by

turning the coarse adjustment knob away from you until the specimen is in focus.

6. Fine tune the focus with the fine adjustment knob.- do not use the coarse adjustment knob after this point!

7. Change objectives and re-fine tune the focus.

Proper clean up technique

1. Clean up right away

2. Go back to low power

3. Lower the stage

4. Remove the slide

5. Proper storage1. Check the stage

2. Check the objective

3. Wind the cord

4. Dust cover it

Proper storage technique

1. The stage must be all the way down.

2. The low power objective must be in place.

3. The slide must be removed.

4. The cord must be wound around the base.

5. The dust cover must be replaced.

How to make a wet-mount slide …

1 – Get a clean slide and coverslip.

2 – Place ONE drop of water or stain in the middle of the slide. Don’t use too much or the liquid will run off the edge! Place the specimen in the drop.

3 – Place the edge of the cover slip on one side of the liquid drop.

Hold the coverslip at a 45-degree angle in the edge of the puddle.

5 –Place the slide on the stage and view it first with the low power objective. Wash and dry the coverslip and slide when finished. Once you se the image, you can rotate the nosepiece to view the slide with different objective lenses.

5 - Slowly lower the cover slip on top of the drop with fingers or forceps. Cover Slip

Lower slowly

You do not need to use the stage clips when viewing wet-mount slides!