chapter 2 scientific investigations
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SCED 475, Fall 2009 by Dr. Song
CHAPTER 2: SCIENTIFIC INVESTIGAIONS
WILL IT FLOAT OR SINK?
Orange Lemon Lime Banana
Apple
Watermelon
Un P.
Peeled
Un P.Peele
dUn P.
Peeled
Prediction
Observation
Inference
1. DESCRIPTIVE INVESTIGATION
: gather observational and measurement data to answer questions about the properties and actions of objects, organisms, events, and systems
2. CLASSIFICATORY INVESTIGATION
: organize collected information by sorting and grouping it according to one or more properties in order to identify relationships and better define properties
GRANDFATHER CLOCK
What will change the speed of my pendulum in my grandfather clock so that I keep time correctly?
EXPERIMENTAL INVESTIGATION
: conduct experiments, including controlled experiments, to determine how variables are related and to isolate causal factors in nature phenomena
HYPOTHESIZING – PP. 40-41
Hypothesis: a suggested explanation for a phenomenon (which is observable): a reasoned proposal suggesting a possible correlation between multiple phenomena : a statement about a possible answer to a question that might be found through investigating
Informed by background knowledge, prior knowledge, experiences
Can be modified as inquiry progresses
EXPERIMENT (VARIABLES) – PP. 41-42
Variables: something that can vary or change in a situation : something that can affect the outcome of the experiment
Manipulated Variables (independent V): The variable which is purposefully changed in a situation
Responding Variables (dependent V): The variable which may change or be affected as the result of the manipulation
Controlled Variables: The variable which are purposefully held constant or stable in a situation
EXPERIMENT (TRIALS)
How many times? Multiple trials => averaged
DATA COLLECTION AND INTERPRETATION
Line graph: Show changes in variables over time: Continuous variables (e.g. time, temperature)
Bar graph: Show differences in data: Numerical data related to categories - Discrete variables (e.g. the # of legs of an animal)
Data table Graphing (pp. 36-38)
: Pictorial representation of data=> See some patterns or relationships
DATA COLLECTION AND INTERPRETATION Histogram
: the number of times a number even occurs in a large set : a graphical display of tabulated frequencies, shown as bars: shows what portion of cases fall into each of several categories
CONCLUSION
A statement which summarizes a set of observations made regarding some particular phenomenon
Your data support (accept) / do not support (reject)
HOW DOES MY PENDULUM CLOCK WORK?
PENDULUM
Something hanging from a fixed point which, when pulled back and released, is free to swing down by force of gravity and then out and up because of its inertia
Law of inertia: A body in motion will continue in
motion, unless acted upon by a force
PENDULUM
Period: time for one swing
of the pendulum over and back
Frequency: the number of
back and forth swings in a certain length of time
INVESTIGATIONS
M & M
INVESTIGATION WITH M & M
What happens when an M & M is placed in a plate of room-temperature water?
Pour room-temperature water into a white plastic or foam plate so that it covers the bottom of the entire plate. Once the water has settled, place 1 M&M in the center of the plate. Be careful to keep the water and M&M as still as possible. Observe for about 1 minute.
From: Inquiry in Action (3rd ed.) by American Chemical Society
Dissolving: Interaction between the molecules of the solvent (the liquid doing the dissolving) and the molecules of the solute (the substance being dissolved)
INVESTIGATION WITH M & M
Questions you could investigate Do some M & M colors dissolve in water faster than others? What would the colors look like if we place two or more M &
M’s in a plate of water? Does the temperature of the water affect how fast the
colored coating dissolves from an M & M? Does the amount of sugar already dissolved in water affect
how fast an M & M coating dissolves?
Variables that will effect on the way M & M’s dissolve in water Color of the M & M’s The number of M & M’s The temperature of water Type of liquid & the concentration of the solution in which
the M & M’s are placed
WHAT HAPPENED? & WHY?
Because of the way oxygen and hydrogen atoms are bonded together, a water molecule has an area of positive charge and an area of negative charge. This makes the water a polar molecule. (The water molecule has no overall or “net” charge. It is neutral.)
Because of water’s polarity, water molecules are attracted to each other.
WHAT HAPPENED? & WHY?
Sugar (sucrose) also has oxygens and hydrogens bonded to each other. This gives sucrose many areas of positive and negative charge.
WHAT HAPPENED? & WHY? Water and sucrose are attracted
to one another based on the attractions of opposite charges.
When the attraction that water molecules have for sucrose overcomes the attraction sucrose molecules have for each other, the sucrose dissolves.
The polar nature of water is what makes water so good at dissolving many substances.
HOW SMALL?
The drawings and models of water molecules that you see or build are millions of times larger than the actual size of real water
molecules. To get an idea of how small they are, consider this: Let’s say you had about a tablespoon of water and wanted to count all the water molecules in that amount of water.
Assume you were a very fast counter and could count 1 million water molecules every
second. Even at your very fast counting speed, it would take you over 190 million
centuries to count all the water molecules in that small amount of water. WOW!