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!