Variables
This variable changes as a result of manipulating a different variable in the experiment. It is usually represented on the y-axis of a graph.
Dependent variable
The purpose of this part of Experimental Design is to make a prediction (based on what you already know) about WHAT results an experiment will show and WHY you think that.
Hypothesis
Which axis (x or y) normally shows the independent variable (what is manipulated in the experiment)?
X-axis
True or false? The correct order in size/scale from largest to smallest is:
macroscopic, submicroscopic, microscopic
False.
It's macroscopic, microscopic, submicroscopic
H2O and CO2 are examples of chemical formulas. What level of observation are these examples of?
Symbolic level
These variables are kept the same each time you repeat an experiment. You never change them.
Constants (constant variables)
When writing a hypothesis, students are encouraged to write an if-then statement. Which variable is described after "then"?
Dependent variable
Why must data analysis happen before making a conclusion?
It is important to take time to look at the data and recognize patterns in order to understand the relationship between variables.
Human beings observe the world around them at the ____ level.
This is often included in many models/diagrams and serves to explain what different symbols/shapes/colors mean.
This variable is the one manipulated by the scientist; it is hypothesized to have some effect on another variable
Independent variable
Why is it so important that procedures and materials be written VERY specifically?
To allow others to reproduce your experiment EXACTLY and verify that the same results can be achieved
Is interpretation an objective or subjective process? Briefly explain.
It is subjective. The way one person interprets a set of data could be different from the way another person does.
Why is the microscopic level not sufficient for most of what is studied in chemistry?
Atoms and molecules are too small, even for the best microscopes. We need to observe at the submicroscopic level.
Write an appropriate hypothesis statement for the following testable question:
"What is the effect of the amount of caffeine on the speed at which Mr. D talks?"
If Mr. D consumes more caffeine, he will talk faster because he will be hyper. (Results may vary)
Why is it important to have only one independent variable and to keep all other variables constant in an experiment?
If there is more than one independent variable, you won't know what caused the change in the dependent variable.
This section of an experimental design serves to make others aware of potential dangers about the materials or procedures used in the experiment
Safety Considerations
What is the purpose of considering errors in an experimental design?
It allows the scientist to consider if any results may be flawed and whether repeating the experiment differently is necessary.
Describe what a water molecule would look like at the submicroscopic level, as you have seen them represented in class
There should be three atoms. The one in the center is slightly larger and a different color than the other two atoms. The overall shape looks like Mickey Mouse.
What is the difference between data analysis and data interpretation?
In data analysis, you take raw data and clean it up, often by making a graph. It may also include doing some math (finding averages, using formulas, etc.) In interpretation, one tries to make sense of the data. (What does it mean?)
A young scientist wants to know how heating or cooling a battery will affect the life of the battery. Identify the IV and DV.
IV = temperature (heating or cooling); DV = battery life (time)
What was the general purpose of doing different Alka-Seltzer experiments?
(Results may vary) We wanted to know how different factors could affect the rate of reaction of the ingredients in the Alka-Seltzer tablet (citric acid + sodium bicarbonate)
A graph is made with the independent variable represented on the x-axis and dependent on the y-axis. It has a positive slope (/). What is the relationship between these variables?
As the independent variable increases, the dependent variable increases (direct relationship)
Describe what you would see if you looked at purified bottled water under a microscope
NOTHING (unlike pond water--which you saw last year in biology--there should be no visible particles, still or moving, in filtered/purified water)
What would be an appropriate interpretation for a graph that shows 0 slope (----)?
(X-axis: independent, Y-axis: dependent variable)
The independent variable has no effect on the dependent variable.