1. Snail lab prep notes
William and Tell broadcast system
Table on chalkboard:
Name Wt (g) warm spd (cm/m) cold spd (cm/m)
Hand out by size-class, then designate limits of size
classes based on actual weight data, e.g., <3.5g,
g, >6.5g).

2. Snail races lab Read pages 1-3 in lab manual
Soundtrack for William and Tell Overture

3. Part 1:
Background:
The Metric System and the Scientific Process

4. The Realm of Science
By its nature, science deals with detectable things in nature
Undetectable or supernatural phenomena fall within the realms of philosophy and religion

5. Experimental or Hypothetical-deductive (H-D) Science
Used for most modern research
Follows the Scientific Method
Procedures that ensure reliable conclusions
Sometimes abbreviated as O.H.E.C.
Number of steps can vary

6. Scientist observes some phenomenon
Step 1: OBSERVATION (O.)
Scientist observes some phenomenon
Considers it unique or worthy of investigation
Give example

7. Step 2: HYPOTHESIS (H.)
A TENTATIVE EXPLANATION for the phenomenon; a “scientific guess”

8. - Hypothesis is accepted or rejected
Step 3: EXPERIMENTAL TESTS (E.)
EXPERIMENTS: re-creation of the phenomenon under controlled conditions
Methods recorded, therefore replicable
- Certain FACTORS or INFLUENCES are manipulated
- E.g., set to high, medium, and low
- Tests are conducted
- Analysis
Usually involves statistics because data are normally samples
- Hypothesis is accepted or rejected
Need 2 examples, with different designs

9. Interpretation of results
Step 4: Conclusions (C.)
Interpretation of results
What do the results mean?
The step most subject to bias
Scientific peers might interpret results differently

10. WIDELY-RECOGNIZED explanations
SCIENTIFIC THEORIES
WIDELY-RECOGNIZED explanations
Based on lots of evidence, scientific tests
Many individual studies
E.g., gravity, evolution
Example of theory vs hypothesis

11. Objectives of today’s lab:
1) Practice taking measurements in the metric system
2) Test the influence of body size and temperature on snail speed

12. Procedures: Lab procedures in general:
Bring a small calculator – or mobile phone
Work in 4-person groups
Most of today’s lab will be individual work
Each person will hand in a worksheet

13. The Metric System Why is the metric system considered more convenient?
Based on multiples of 10
10 millimeters = 1 what?
centimeter
10 centimeters = 1 what?
decimeter
10 decimeters = 1 what?
meter

14. Linear measures What does linear refer to? a straight line
What increment is numbered on the metric scale of your plastic ruler?
A centimeters is about the width of a fingernail
What is the smallest metric increment on your plastic ruler?
What is the total length of your ruler in cm?
In mm?
What increment is numbered on the English scale of your plastic ruler?

15. This?
This?
This?
This?
This?
This?
What is this?

16. What is half of a 16th?
Half of a 32nd?
Fractions of an inch also have decimal equivalents:
1/4 =
1 ÷ 4 =
0.25

17. Weight measures
Also multiples of 10 in the metric system:
1 kilogram = 1,000 grams
1 gram = 1,000 milligrams
English system:
__ oz = 1 lb 16
2,000
____ lbs = 1 ton

18. Volume measures
How would you define the volume of something?
The 3-D space it occupies
Volumes of cubes are straightforward
E.g., 1 cm3 = 1 cm x 1 cm x 1 cm
How would you determine the volume of a snail?
By Displacement of Water
Start with any amount of water
Submerge the snail
Record the increase in total volume

19. The top is curved up on the sides
Read the meniscus from the bottom
The top is curved up on the sides
Water adheres to the plastic
Read here
Meniscus
Adhesion

20. Final point on the metric system
Universality:
Conversions can easily be made between lengths, volumes, and weight:
1 ml of water (at “STP”)
= 1 cm3 of water
= 1 g of water

21. Accuracy: degree of agreement between a
measured value and the accepted value. 
Precision: extent to which a set of measurements
agree with their mean

22. Take a snail of the size provided by the instructor
To lift snails, drag them sideways
Small snails have thin shells – don’t squeeze
Determine range of sm, md, and lg categories
(e.g., <3, 3-6, >6)
Name your snail

23. Measure your snail’s width and length
Measure first using centimeter scale of your ruler
Then use inch scale, recording in fractions
What is a numerator?, denominator?
Actually measured
Calculated from left to right
For calculation, 1-1/16 = 17/16 (for example)
No “naked decimals”: e.g., > 0.02, 5 -> 5.0

24. Weigh your snail
Must “tare” the scale so weight of “weigh-boat” will be ignored
i.e., do not include weight of weigh-boat
1) Place empty boat on scale
2) Press tare button
3) Place snail on boat
4) Record weight

25. Measure your snail’s volume by displacement of water
Choose an appropriate sized cylinder
larger diameter than your snail
Start with enough water to fully immerse the snail
Increments on cylinders are in milliliters

26. Part 2 The races (experimental tests): Propose your hypotheses:
1) the influence of size on speed
2) the influence of temperature on speed
5 warm races, 60 seconds each
5 cold races, 60 seconds each
Return to ice after each race

27. Part 3, observation
(respiratory pore)
(smell)
(touch)