Day 3: Experimental Lab Design
Different approaches to Field and Lab Research
Objectives: Students will learn basic primary research and lab skills utilizing the scientific method.
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Lesson Plan Notes:
- First, have the students look at their list of observations from the previous experiment
- Next have them form a question based on a common observation.
- Next have them form their own, emphasis - Their own hypothesis. I want different opinions / hypotheses within each group.
- Next discuss the different variables (see below)
- Use a pencil to model an experiment (see below)
- Point out that the independent variable is the one that "I" change.
- Point out that the dependent variable is the one that responds to the change - and its the one I'm observing and/or measuring as a result of the change
- Point out that the remaining variables must be kept the same every time.
- Point out how to identify the independent and dependent variables in their questions and hypothesis (see examples below).
- Have students write down the scientific dialogue below - then go over the independent and dependent variables and how to identify them.
- Point out that the original question will always have the dependent variable
- Point out that the original hypothesis will always have the independent variable
- Point out that the revised question blends both the original question and hypothesis
- Point out that the revised question will also start out with the phrase "how" followed by the independent variable affecting the dependent variable.
- Point out that the revised hypothesis will always start out with "if" and will always contain the independent variable and describes how you plan on changing it.
- Point out that the "then" will always contain the dependent variable and describes the expected outcome.
- Point out that the because portion contains the hypothesis - or the reason behind the expected outcome.
- Point out that the expected outcome is vitally important - as it helps you know if your hypothesis is in the right direction. If your results comes back negative - then you need to revise your hypothesis.
- Have students identify their own independent and dependent variables from their own set of questions - and move through the packet up to procedures, materials and expected outcome on page 6.
- Explain that you will be going around to helping them not only identifying, but also individually walk them through their revised experimental question & revised hypothesis based on their own question & hypothesis. (This takes up the most of the time - it will go fast if you're not careful).
pencil Experiment metaphore
In today's lesson - I walked students through the scientific method - step by step and discussed what each variable is in an experiment.
To explain what a controlled experiment looked like - I used a pencil as my metaphor. (Please click on the image to the right to enlarge it).
- Variable: Any factor that can change in an experiment.
- Independent Variable: the factor that "I" change in an experiment.
- Dependent Variable: the factor the "depends" upon what "I" changed in the experiment. (the one you observe/measure)
- Controlled Variable: the factor that does NOT change in an experiment.
- Controlled Experiment: an experiment in which all factors except one are kept constant. This is the experimental setting considered the norm - that all other experiments are compared to.
To explain what a controlled experiment looked like - I used a pencil as my metaphor. (Please click on the image to the right to enlarge it).
- First I point out all of the variables of this metaphorical experiment. The pencil, the eraser, the position (or the angle) of the eraser, the tip, the position (or angle of) the tip, the graphite, the color of the pencil, the fingers, the placement of the fingers etc.
- Next I take my finger and push down the eraser of the pencil then ask - what did "I" change? The students of course point out the angle or position of the eraser.
- I then ask - what variable was that then? Answer: the independent variable.
- I next ask what responded? Answer: the position or angle of the tip.
- I then ask - what variable was that then? Answer: the dependent variable.
- I then ask if I changed anything else. Answer: no
- I then ask - what variable was that then? Answer: the controlled variables
- I then ask - why is it important that I not change two variables? Answer: because then you don't know which variable caused the change.
How to identify the independent & dependent variables in the question & hypothesis statements
When trying to set up your next experiment - it would be nice to know how to identify your independent and dependent variables. To put it simply:
The dependent variable is found in the question, and the independent variable is found in the hypothesis statement.
Let's try a few:
Question 1: Why did the tail side seem to hold more water drops?
Hypothesis 1: Because the tails side had a higher ridge.
Even though the independent variable from the previous experiment was the two sides of the coin (heads v. tales), as we set up the next experiment, the reasoning in the hypothesis provides the reason why we may have had more water drops. Therefore, in your next experiment - we would first examine to see if there truly is a difference in height (field research question), followed up with how the height of the ridge affects the number of water drops (cause & effects question). Therefore, the dependent variable for the next experiment will be the number of drops. while the independent variable would be the height of the ridge.
Question 2: Why did we get different results (number of drops) on each trial?
Hypothesis 3: It's because of the different heights the drops were dropped from.
As stated once again, notice that the independent variable in your next experiment would be the different heights as found in the hypothesis, while the dependent variable would be the number of drops once again as found in the question.
Question 3: Why did the water form a dome shape on top of the penny?
Hypothesis: It's probably because of the waters cohesive property.
Here, the hypothesis once again contains the independent variable - the cohesive property of the water, while the question sets up our dependent variable concerning the shape of the water. In our next experiment - we will need to disrupt the cohesive property of water by adding soap to one jug of water and comparing to the number of drops of regular water.
The dependent variable is found in the question, and the independent variable is found in the hypothesis statement.
Let's try a few:
Question 1: Why did the tail side seem to hold more water drops?
Hypothesis 1: Because the tails side had a higher ridge.
Even though the independent variable from the previous experiment was the two sides of the coin (heads v. tales), as we set up the next experiment, the reasoning in the hypothesis provides the reason why we may have had more water drops. Therefore, in your next experiment - we would first examine to see if there truly is a difference in height (field research question), followed up with how the height of the ridge affects the number of water drops (cause & effects question). Therefore, the dependent variable for the next experiment will be the number of drops. while the independent variable would be the height of the ridge.
Question 2: Why did we get different results (number of drops) on each trial?
Hypothesis 3: It's because of the different heights the drops were dropped from.
As stated once again, notice that the independent variable in your next experiment would be the different heights as found in the hypothesis, while the dependent variable would be the number of drops once again as found in the question.
Question 3: Why did the water form a dome shape on top of the penny?
Hypothesis: It's probably because of the waters cohesive property.
Here, the hypothesis once again contains the independent variable - the cohesive property of the water, while the question sets up our dependent variable concerning the shape of the water. In our next experiment - we will need to disrupt the cohesive property of water by adding soap to one jug of water and comparing to the number of drops of regular water.
Setting up the experimental question & new hypothesis:
First off, we need to understand the nature of asking the question in science. There are two types of research based questions that we'll study this year: Field Research questions (or case study) and Cause & Effect questions. Depending on the nature of the original question and hypothesis will determine the type of follow up question.
Field research based questions are not looking for a causation of any type of changes - but rather discovering the conditions of things as they are. The information gathered may be used in comparison to other aspects related to its self within the confines of the independent variable, but once again, the question spells out the dependent variable. However, in a cause & effect style question - both independent and dependent variables are utilized. Some Field Research style questions can be altered just a bit to a cause & effect style question with a little finesse.
Field Research / Case Study Style Question:
*These questions simply examine the subject as if you were to observe it with a fine tooth comb and a magnifying glass.
Cause & Effect Style Question:
*These questions look for causation relationships, and are the only questions that can be re-written as an "if / then / because" statement.
Field research based questions are not looking for a causation of any type of changes - but rather discovering the conditions of things as they are. The information gathered may be used in comparison to other aspects related to its self within the confines of the independent variable, but once again, the question spells out the dependent variable. However, in a cause & effect style question - both independent and dependent variables are utilized. Some Field Research style questions can be altered just a bit to a cause & effect style question with a little finesse.
Field Research / Case Study Style Question:
- How many divots does each side of the penny have?
- How many scratches does the ridge have?
- How high is the ridge on both sides of the coin?
- How much volume does the head image occupy compared to the building/shield of the tails side?
- How many scratch marks are on each side of the penny?
- Does the ridge have any scratch marks?
*These questions simply examine the subject as if you were to observe it with a fine tooth comb and a magnifying glass.
Cause & Effect Style Question:
- How does soap affect the number of drops a penny can hold (soap affects the cohesion of water)
- How does the number of divots affect the number of drops a penny can hold (comparing smooth to an imaged side - both sides of the coin must contain ridges).
- How does the ridges height affect the shape of the dome? (comparing a ridged coin vs. a totally smooth sided coin).
- What liquids reduce the cohesion of water?
*These questions look for causation relationships, and are the only questions that can be re-written as an "if / then / because" statement.
How to convert Cause and Effect questions to "If / Then / Because" hypothesis statements:
In order to restate your hypothesis with an "if / then / because" statement, the question needs to be rephrased as a cause & effect question, as it will not work well with a field research based question. Example:
To do this, use the generic formula below to fill in the blanks.
Original Question:
Original Hypothesis:
Revised Question:
Revised Hypothesis:
Notice how this flows much like a normal conversation. Watch how it works:
Original Question: Why did we have different results after every test?
Original Hypothesis: Probably because we dropped the water droplets at different heights.
Revised Question: How does the height of the water droplets affect the number of drops a penny can hold?
Revised Hypothesis: If I increase the height of the water droplets, then the number of drops a penny can hold will go down because of the increased disturbances due to the increased speed at which the drop hits the penny.
- Revised Question: How does the ridges height affect the shape of the dome?
- Revised Hypothesis: If I decrease the ridges height of a penny, then the dome shape will be thinner because the ridges help to trap the watery contents on top of the penny.
To do this, use the generic formula below to fill in the blanks.
Original Question:
- Why does the (dependent variable) do (description of observation)?
Original Hypothesis:
- Use the independent variable as a possible explanation for a set of observations
Revised Question:
- How does (the Independent Variable) affect (the Dependent Variable)?
- Notice that the revised question restates the original question by blending the original question with the hypothesis - like a normal conversation.
Revised Hypothesis:
- If I (describe how you are going to manipulate the independent variable),
- then the (dependent variable) will (describe your expected outcome if your hypothesis is correct)
- because (describe and explain your hypothesis from this point forward).
Notice how this flows much like a normal conversation. Watch how it works:
Original Question: Why did we have different results after every test?
Original Hypothesis: Probably because we dropped the water droplets at different heights.
Revised Question: How does the height of the water droplets affect the number of drops a penny can hold?
Revised Hypothesis: If I increase the height of the water droplets, then the number of drops a penny can hold will go down because of the increased disturbances due to the increased speed at which the drop hits the penny.
Your turn:
You and your group formed a question based on an observation from the previous experiment. Your job is to take that question and identify the independent and dependent variables, then convert them to a cause and effect question - which then will be turned into if' / then / because hypothesis statements.
Finish the next page, where you are to identify the materials and procedures of your next experiment.
Finish the next page, where you are to identify the materials and procedures of your next experiment.
Continue reading if you are struggling with your question & hypothesis statements:
After determining what variables we want to work with, we need to rephrase the original question as a testable question. Below is a generic version of the question statement.
Let's say that our original question was "How does salt affect waters cohesion?". Let's also say that our hypothesis was that salt will get in between two water molecules and weaken the attraction between the water molecules. Our next step would be to consider any possible variable that would be remotely associated with the experiment. Below is our list of variables.
Variables:
Next, we pick out the variables that I am changing and manipulating - as found in our question and hypothesis. Since our original question is about salt and how it affects cohesion - the amount of salt is a better determinant than the type of salt, and we can't directly determine the cohesiveness of water - but we can indirectly determine it by the number of drops. Therefore, when we rephrase the question it might look something like this:
This question turns a general question like "how does salt affect the cohesive property of water" into a more specific testable question - that is still reflective of the original question.
Our next step (fifth) is to create a testable hypothesis.
Since our original hypothesis reflects how the cohesive properties of water would be weakened because the salt molecules would get in between two water molecules, we should expect to see the number of drops go down as a possible outcome. Therefore, when we write the refined hypothesis it should reflect the experiment and explanation of the possible outcome if proven correct.
The generic version of a hypothetical test statement looks like this:
In our example - our refined hypothesis statement might look something like:
This now describes the premise of your experiment and basically how you plan on carrying it out.
Our final step at this point before carrying out the experiment is to come up with a list of procedures and the list of materials you will need to carry out your experiment.
With procedures - be sure that they are precise and detailed. It needs to be written in a way that others can follow.
After determining what variables we want to work with, we need to rephrase the original question as a testable question. Below is a generic version of the question statement.
- How does the (independent variable) change the (dependent variable)?
Let's say that our original question was "How does salt affect waters cohesion?". Let's also say that our hypothesis was that salt will get in between two water molecules and weaken the attraction between the water molecules. Our next step would be to consider any possible variable that would be remotely associated with the experiment. Below is our list of variables.
Variables:
- Amount of salt
- Amount of water
- Number of drops
- Types of salt
- Pennies used
- Other equipment used
- Temperature of the water
Next, we pick out the variables that I am changing and manipulating - as found in our question and hypothesis. Since our original question is about salt and how it affects cohesion - the amount of salt is a better determinant than the type of salt, and we can't directly determine the cohesiveness of water - but we can indirectly determine it by the number of drops. Therefore, when we rephrase the question it might look something like this:
- How does the amount of salt affect the number of drops of water a penny can hold?
This question turns a general question like "how does salt affect the cohesive property of water" into a more specific testable question - that is still reflective of the original question.
Our next step (fifth) is to create a testable hypothesis.
Since our original hypothesis reflects how the cohesive properties of water would be weakened because the salt molecules would get in between two water molecules, we should expect to see the number of drops go down as a possible outcome. Therefore, when we write the refined hypothesis it should reflect the experiment and explanation of the possible outcome if proven correct.
The generic version of a hypothetical test statement looks like this:
- If I change the (independent variable), then the (dependent variable) will change (describe the possible outcome based on reasons why) because (provide the reasons why here).
In our example - our refined hypothesis statement might look something like:
- If I increase the amount of salt I put in the water, then the number of drops should go down because the salt gets in between the water molecules, which disrupts the attraction of a water molecule to another water molecule.
This now describes the premise of your experiment and basically how you plan on carrying it out.
Our final step at this point before carrying out the experiment is to come up with a list of procedures and the list of materials you will need to carry out your experiment.
With procedures - be sure that they are precise and detailed. It needs to be written in a way that others can follow.
Sources:
different types of scientific questions
what are the different types of scientific investigations
different types of scientific questions
- http://www.goscienceseven.com/SciMethod/sciquestions.html
- https://www.csun.edu/science/ref/science_projects/research_questions.html
what are the different types of scientific investigations
- http://mrcloudsclass.com/attachments/article/9/3%20Types%20of%20Investigations.pdf
- http://study.com/academy/lesson/what-is-scientific-investigation-definition-steps-examples.html
- http://wrmscrue.weebly.com/uploads/2/2/6/3/22635792/staarbooklet.pdf
- http://wrmscrue.weebly.com/uploads/2/2/6/3/22635792/investigation_types.pdf