INFORMATION

• Syllabus• Safety• DO/COLLECT: Pre-lab #2• MICROWORLDS– Four entries due by end of 3rd lab (week 3)

Lab 2: Processes and Tools of Scientific Inquiry

Two Approaches to Science

DISCOVERY SCIENCE• No experiments• Based on observations• Inductive reasoning –

general principles derived from large number of specific observations

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EXAMPLE: All living things are composed of cells

Two Approaches to Science

HYPOTHESIS-BASED SCIENCE• Involves carefully planned experiments• Based on observations• Deductive reasoning – takes a general

statement and extrapolates specific results we would expect

Experimental DesignVARIABLES: things that

might change during the experiment

• INDEPENDENT VARIABLE: what you are changing in the experiment (what you’re testing)

• DEPENDENT VARIABLE: what you are measuring

• CONSTANT VARIABLES: things that are the same between your groups

The DEPENDENT VARIABLE depends

on the INDEPENDENT VARIABLE

The DEPENDENT VARIABLE depends

on the INDEPENDENT VARIABLE

Experimental Design – Controlled Experiments

You generally have two groups:1. CONTROL GROUP (CONTROL TREATMENT):

The group you are going to compare to; the one you don’t do anything to

2. EXPERIMENTAL GROUP: The group(s) on which you are testing something

Controlled Experiment

Control Group Experimental Group

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WATER

WATER +

FERTILIZER

Only once?

• How many times should you do an experiment?

• How should you test multiple samples?

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Sampling Error

• Draw 1 jelly bean?• Draw 10 beans?• Draw 100 beans?• Draw all the beans?

• SAMPLE SIZE: The number of samples, the more the better

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Lab: Black Box Experiment

• Identify what is contained in your box without peeking!

Scientific Notation and the Metric System – Appendix A

• SCIENTIFIC NOTATION: More compact form of a very large or very small number

• The distance to the Sun's nearest neighbor Alpha Centauri is greater than 10,000,000,000,000,000 m.

Tools for Scientific Inquiry: Scientific Notation

• Tells you how many times you must multiply or divide by 10 to get the number

• A number x 10B

• The distance to the Sun's nearest neighbor Alpha Centauri is greater than 1 x 1016m.

Tools for Scientific Inquiry: Scientific Notation

• 1 x 1016 positive number = multiply by 1010000000000000000• 1 x 10-16m negative number = divide by 100.0000000000000001

Tools for Scientific Inquiry: Scientific Notation

• MULTIPLICATION: Add the exponentsEX: (2 x 104)(3 x 105) = 6 x 109

20000*300000 = 6000000000• DIVISION: Subtract the exponentsEX: (6 x 109) / (3 x 105) = 2 x 104

6000000000 / 300000 = 20000

Tools for Scientific Inquiry: The Metric System

Metric System• Science uses the metric system. • The metric units are: – meter for distance (measurement from one point to

another) – liter for volume (ie, the space that 1 liter of water

occupies) – gram for mass (weight), – and degree Celsius for temperature.

• metric units do not advance like English: grain, ounce, pound, ton

• they advance using prefixes & powers of ten

Metric how-to

• It’s all about powers of TEN

Metric Prefix Meaning

kilo (kilometer, kilogram) 1000

meter, liter, gram 1

centi (centimeter, centiliter, centigram)

1x10-2 (1/100  or  0.01)

milli (milliliter) 1x10-3

micro (micrometer)1X10-6   (distance in microscopes)

nano  (nanometer)1X10-9   (distance in electron microscopes)

Metric units are convertible. • 1 cubic centimeter (or 1 cc) of water is equal to

1 milliliter (ml) which is equal to 1 gram of water at sea level.

• This does not work if water is not the material of study!

Metric System

Basic Metric Measurements• You will measure water in a

cylinder, tends to stick to the sides, especially with glass.

• This makes the meniscus, the boundary between the air and the water, curved.

• The correct way to read it is to read it from the bottom of the meniscus!

Converting Units

• Set up equations to cancel out units

200 m = cm200 m * 1 x 102 cm = 20000 cm = 2 x 104 cm

1 m

•THINK ABOUT YOUR ANSWER: Should there be more cm than m? Should there be fewer?•DOES YOUR ANSWER MAKE SENSE??

•THINK ABOUT YOUR ANSWER: Should there be more cm than m? Should there be fewer?•DOES YOUR ANSWER MAKE SENSE??

Practice Question

250 cm =• Meters?

• Millimeters?

Measurements

Accurate• How close is the

measurement to the true value?

Precise• How consistently can a

measurement be reproduced?

Measurements• Use a measuring tool that is close to the

measurement you want to make

Lab: Appendix A - Measuring

• Read the information in the lab• Practice measuring with a pipette, graduated

cylinder, balance, ruler/meter stick• Be able to answer the questions in the Study

Guide in preparation for the quiz next week!