Science Skills

• The common steps that all scientists use to investigate or do an experiment is called the SCIENTIFIC METHOD.

Methods of Science

• The first step of the SCIENTIFIC METHOD is to CHOOSE A PROBLEM; this often takes the form of a question.– E.g. What effect does caffeine have on the

growth of the Arabidopsis plant?

1. Choose A Problem

Caffeine

Arabidopsis

?

• Before continuing with the experiment a scientist should RESEARCH THE PROBLEM

• Ways to research:– Make and record observations– Talk to experts– Go to the library or browse the internet

2. Research Your Problem

• A HYPOTHESIS is a prediction that can be formally tested; it is based on your observations and research.

– An educated guess about what will happen

• E.g. Caffeine will cause an increase in the growth of the Arabidopsis plant.

3. Develop A Hypothesis

• An EXPERIMENT is an investigation that tests a hypothesis by collecting data under controlled conditions.– A controlled experiment often has 2 groups:

The CONTROL group and the EXPERIMENTAL group

4. Design An Experiment

WITH caffeineNO caffeine

CONTROL Group EXPERIMENTAL Group

VS.

(nothing changed) (one variable changed)

• The CONTROL is the part of the experiment that is the standard against which the results are compared.– E.g. Group of 10 plants WITHOUT caffeine

added

The EXPERIMENTAL group is the group that has ONE variable changed.– E.g. Group of 10 plants WITH a measured

amount of caffeine added

Design An Experiment

• The ONE thing that is CHANGED in an experiment is called the INDEPENDENT VARIABLE– E.g. Independent variable is the amount of

caffeine added to the plants

Independent Variable

Independent Variable

Caffeine

• The DEPENDENT VARIABLE is the MEASURED result caused by the independent variable.– The dependent variable DEPENDS on the

independent variable• E.g. The dependent variable is the measured

growth of the plants

Dependent Variable

• The DEPENDENT VARIABLE is the result of the INDEPENDENT VARIABLE being manipulated.– E.g. More caffeine (Ind. Var.) = more plant growth (Dep. Var.)

• Independent Variable: scientist CHANGES– Caffeine

• Dependent Variable: scientist MEASURES– Growth

Ind. Vs. Dep. Variable

• In order to TEST YOUR HYPOTHESIS the experiment that was designed must now be conducted.– E.g. Allow both the control group and

experimental groups of Arabidopsis plants to grow for a period of 5 days and record the height of every plant each day in a data table

5. Test Your Hypothesis

Day 1 Day 2 Day 3 Day 4 Day 5

Caffeine 1.4in 2.2in 3.9in 5.0in 8.5in

Control 1.2in 1.9in 2.7in 4.1in 6.5in

• DATA is defined as any information that is obtained from an investigation

• The DATA that has been collected must then be ORGANIZED

• Usually the DATA will be put into a chart or graph to provide visual results that can be more easily interpreted

6. Organize Your Data

Effects of Caffeine on Arabidopsis Plant Growth

• The data that has been collected in the experiment must then be ANALYZED and the scientist must come to a CONCLUSION

• The CONCLUSION must indicate whether the hypothesis was accepted or rejected– E.g. Looking at the data, the hypothesis that

caffeine will increase Arabidopsis growth is confirmed

7. Draw Conclusions

• Once a conclusion has been drawn a scientist will then PUBLISH the results to share with other scientists

• Other scientists can try to replicate the results by repeating the same procedure

Draw Conclusions

• A hypothesis that is supported many different times by many different scientists will become a THEORY

• A THEORY is NOT a guess!! A THEORY is CONFIRMED by scientific observations. – E.g. Theory of Gravity, Atomic Theory, Theory of Evolution

Hypothesis Becomes A Theory

Science Skills

Le Système International d’UnitésSI

Units Universally Used by ScientistsWith exceptions

British EngineeringFoot, slug, BTU

• All scientists use the same system of measurement called the INTERNATIONAL SYSTEM OF MEASUREMENT (SI).– Meter (length)– Gram (mass)– Liter (volume)– Second (time)– Celsius degree (temperature)

• Scientists around the world communicate quantitative data using the SI system

International System of Measurement (SI)

Science Skills

SI Units (Base)Length – meter (m)Mass – kilogram (kg)Time – second (s)Temperature – Kelvin (K)Amount – mole (mol)

Science Skills

SI Units (Derived)Area – square meter (m2)Volume – cubic meter (m3)Density* – kilogram/cubic meter (kg/m3)Pressure – Pascal kg/m*s2 (Pa)Energy – Joule kg*m2/s2 (J)

Science Skills

Greek PrefixesMultipliers of SI Units

Giga G 109 1,000,000,000 Mega M 106 1,000,000Kilo k 103 1,000Centi c 10-2 0.01Milli m 10-3 0.001Micro 10-6 0.000001Nano n 10-9 0.000000001

1Mm

106m

109nm

1m

Name Symbol Size factor or

 nano

 n

 10-9

 micro

 m

 10-6

 milli

 m

 10-3

 centi

 c

 10-2

         

 kilo

 k

 103

 Mega

 M

 106

109nm

1m

1m

109nm

106m1m

1m

106m

103mm

1m

1m

103mm

102cm

1m

1m

102cm

1km

103m

103m

1km

1Mm

106m

106m

1Mm

Science Skills

Scientific NotationWriting REALLY BIG or really small numbers

easily

11109000,000,000,900 x

9101000000001.0000,000,000,1/1 x

Science Skills

Scientific NotationAlways Have ONLY ONE Number to the Left

of the Decimal Point

410324.9240,93 x

41087.1000187.0 x

Science Skills

Converting Unit QuantitiesExamples (cont.):40ns = 1s/10^9 ns= 4x10-8s

Science Skills

Converting Unit QuantitiesExamples (cont.):

12km = _____________m225mm = ____________m34cm = ______________m650nm = _____________m

Science Skills

Converting Unit QuantitiesExamples (cont.):

180g = _____________kg125mg = ____________kg43g = ______________kg

Science Skills

Converting Unit QuantitiesExamples (cont.):

450ns = _____________s22min = ____________s4hrs 12min = ______________s

Science Skills

MeasurementPrecision

Your Ability to Reproduce Measurements

AccuracyHow Close is Your Measurement to the

Actual Measurement?

AccuratePrecise

Science SkillsPresenting Data

Tables

Graphs

Letter Grade # of Students

A 3

B 7

C 10

D 2

F 1Grade Distribution for Spring 2007

Grade Distribution for Spring 2007

0

2

4

6

8

10

12

A B C D F

Letter Grade

# o

f S

tud

en

ts

Grade Distribution for Spring 2007

3, 13%

7, 30%

10, 44%

2, 9%

1, 4%

A

B

C

D

F

Line graph

Pie graph

Bar graph

Science Skills

GraphsVariables

Independent Variable (IV)Manipulated by the ExperimenterRepresented on the “x” axis

Dependent Variable (DV)The Measured VariableRepresented on the “y” axis