PreAP ChemistryChapter 1 Notes

Scientific Method

Scientific Method

The Scientific Method is a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.

Scientific Method

There are two kinds of data that can be observed and collected: Qualitative and Quantitative.

Scientific Method

There are two kinds of data that can be observed and collected: Qualitative and Quantitative.

•Qualitative data is data about qualities, like appearance and behavior.

Scientific Method

There are two kinds of data that can be observed and collected: Qualitative and Quantitative.

•Qualitative data is data about qualities, like appearance and behavior.

What qualitative data can be made about this apple?

Scientific Method

There are two kinds of data that can be observed and collected: Qualitative and Quantitative.

•Qualitative data is data about qualities, like appearance and behavior.

•Quantitative data is data about quantities, like mass, density, and other numerical amounts.

Scientific Method

There are two kinds of data that can be observed and collected: Qualitative and Quantitative.

•Qualitative data is data about qualities, like appearance and behavior.

•Quantitative data is data about quantities, like mass, density, and other numerical amounts.

What quantitative data can be made about these apples?

Scientific Method

A hypothesis is based on previously collected data and is an attempt to explain the data, as a testable prediction; if A, then B. (It may not necessarily contain the words “if” and “then”). A hypothesis is tested with an experiment.

Scientific Method

A hypothesis is based on previously collected data and is an attempt to explain the data, as a testable prediction; if A, then B. (It may not necessarily contain the words “if” and “then”). A hypothesis is tested with an experiment.

What if we ask:

“Do different colors of light affect the growth of a green bean plant?”

Is this a hypothesis? Is it testable? Is it a prediction?

Scientific Method

A hypothesis is based on previously collected data and is an attempt to explain the data, as a testable prediction; if A, then B. (It may not necessarily contain the words “if” and “then”). A hypothesis is tested with an experiment.

What if we ask:

“Do different colors of light affect the growth of a green bean plant?”

Is this a hypothesis? Is it testable? Is it a prediction?

How can this be phrased to be a prediction?

Scientific Method

In an experiment, usually the affect of one variable on another is tested. The variable that is being controlled directly by the experimenter is the independent variable. The independent variable should then have an affect on the variable being tested, called the dependent variable.

Scientific Method

In an experiment, usually the affect of one variable on another is tested. The variable that is being controlled directly by the experimenter is the independent variable. The independent variable should then have an affect on the variable being tested, called the dependent variable.

What is the I.V.?

What is the D.V.?

Scientific Method

Often there are additional variables that can be involved in an experiment, so care should be taken to be sure that these are held constant.

In addition, to judge if the independent variable actually did affect the dependent variable and nothing else, a control situation should be used.

This could be a separate specimen to which the independent variable is purposely held constant or is in the ‘usual’ state, or could be a separate trial of the same experiment, during which the independent variable is held constant or in the ‘usual’ state.

What needs to be constant?

What is the control?

Scientific Method

If a hypothesis is not disproved after many experiments to test it, then the hypothesis is considered a theory, like gravity or evolution.

Scientific Method

If a hypothesis is not disproved after many experiments to test it, then the hypothesis is considered a theory, like gravity or evolution.

Sorry guys, they’re still just theories

Graphs

Why bar and pie graphs

suck and line graph rules.

lack

Bar graphs only show counted objects.

They are not useful for finding connections between variables.

Pie (circle) graphs show the parts of the same whole, in percentage form.

They are not useful for finding connections between variables.

Line Graph Rules

1. Give your graph a title of “dependent variable” versus “independent variable”. This goes neatly at the top and middle of the graph (not necessarily of the piece of paper).

2. Label each axis and indicate the units used. The independent variable always goes on the x-axis and the dependent variable always goes on the y-axis.

3. Number the axes in equal increments. You don’t have to label every line, but don’t change the amount of spacing of each successive line. Your scale should cause the graph to take up as much (at least 60%) of the graph paper as possible. You do not always have to start the origin at (0,0). Consider each time if it is appropriate or not for that particular graph.

DO NOT DO THIS, EVER!

4. Locate the data points you place on a graph with an “X” or a dot with a circle around it. This allows the points to be easily seen once the line is drawn.

YES

YESNO

5. All line graphs should use best-fit lines that are either a straight line (use a straight edge) or a smooth curve (free-hand carefully). Your data should indicate which type of line to use.

Never use a connect-the-dots line. Your line does not have to go through all your data points (but get it close). This shows the uncertainty associated with each measurement, and takes an average of the data.