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Room 34 Online Text
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8.3: Structure of Matter
8.4: Solar System
8.6: Chemistry of Living Things
8.7: Periodic Table
8.8: Density & Buoyancy
8.9: Investigation & Experimentation
8.9 Investigation and Experimentation
Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
Plan and conduct a scientific investigation to test a hypothesis.
Evaluate the accuracy and reproducibility of data.
Distinguish between variable and controlled parameters in a test.
Recognize the slope of the linear graph as the constant in the relationship y=kx and apply this principle in interpreting graphs constructed from data.
Construct appropriate graphs from data and develop quantitative statements about the relationships between variables.
Apply simple mathematic relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed, density, pressure, and volume).
Distinguish between linear and nonlinear relationships on a graph of data.
What the Standard Means - Student Speak
For standard 8.9 students need to be able to design and conduct their own experiment.........
8.9a- to make a scientific investigation to test a hypothesis
8.9b- to calculate the data accuracy and reproducibility
8.9c- to find the difference between variable and controlled parameters in a test
8.9d- understanding a linear graph (y=kx) linear and nonlinear relationships on a graph
8.9e- to build a correct graph from data and make quantitative statements about relationships in variables
8.9f- to use math skill to determine a missing quantity in a mathematic expression
8.9g- to know the difference between linear and nonlinear relationships
The Scientific Method
is a way scientists answer questions and solve problems. When scientists look for answers, they mostly use the same steps. But there is more than one way to use each step. Scientists use either all of the steps or just a few during an investigation. Some may even repeat some steps or do them in a different order. Choosing a way to use the steps is based on what works
best to accurately answer the question. Scientific methods provide a framework for conducting careful investigations and understanding the natural world.
The first step of the Scientific Method is asking a question. When asking a question this helps focus on the subject being tested. Scientists usually ask questions after making many observations. An observation is any use of the senses to gather information. Saying that the grass is green or birds fly is making an observation. Measurements are observations that are made with tools. Observations can be made (and should be accurately recorded) at any point during an investigation. After asking a question and making observations then you form a hypothesis. A hypothesis is a possible explanation or answer a question. Usually you can use what you have already observed to form a good hypothesis. A good hypothesis is always testable. In other words, information can be gathered or an experiment can be planned to test the hypothesis. A hypothesis that is not testable isn't necessarily wrong. But there is no way to show whether the hypothesis is neither right nor wrong. After forming a hypothesis you test it. You must find if it's a reasonable answer to your question. Testing your hypothesis helps you see if you're going in the right direction or if you're way off. If your hypothesis is way off you must change it. A controlled experiment is a great way to test a hypothesis. A
compares the results from a control group with the results from experimental groups. All factors remain the same except for one. The factors that are kept the same between the groups are called
These factors are held steady. The one factor that changes between the groups is called a
The results will show the outcome of the variable parame
Steps of the Scientific Method
After you collect your data, you must analyze them. Organizing data into tables and graphs makes relationships between information easier to see. Analyzing and organizing data from repetitive tests can help you tell if your data was accurate. It can also help you evaluate your data’s reproducibility. Data are reproducible when you get alike data from many tests. At the last part of an investigation, you must draw a conclusion. You might conclude that your results support your hypothesis. Or you could conclude that your results do
support your hypothesis. If so, you could change the method, collect more information, or ask new questions. Whether or not your hypothesis was supported, the results are always important. The most important step in any analysis is communicating your results. You can write a paper, make a presentation, or create a Web site. Telling others what you learned keeps science going. Other scientists can then conduct their own tests based on your results.
Accuracy and Reproducibility of Data
When a scientist conduct an experiments, they want to collect correct data. They want the answer to be correct. If you place 701 g on a balance and get a mass reading of 152 g, your reading is not correct. Maybe you’re using broken equipment, using the wrong tool, or using a tool incorrectly.
Using a graduated cylinder to measure volume can give a more accurate measurement than using a measuring cup found in the kitchen. Your data will still be wrong if you do not read the volume at the bottom of the meniscus at eye level. To get a correct reading using a ruler, you should look straight down on the end of the object you are measuring. If you move your head to either side, you will get a somewhat different measurement.
When a scientist conducts an investigation, they want their results to be able to be frequent, or reproduced, by other scientists. If the data are not reproducible, then there is no way for the results of the experiment to be supported and acknowledged by other scientists. Data must be reproducible in order for other people to be in agreement with your conclusions.
When scientists analyze data, they often find it helpful to use a single number to describe the entire set of data. Three terms that are used for this purpose are
The mean is found by adding all the data points together, then dividing the sum by the total number of data points.
Mode is the number that appears most often in a data set. And median is the value of the data point in the middle when the data are placed in order from smallest to largest. The median is especially helpful when one data point is much smaller or larger than the rest of the data points.
To find the slope of a line, it is helpful to use
. Rise represents a vertical (up and down) change. Run represents a horizontal (side to side) change. For a line on the coordinate plane, the change in
, or the rise, indicates the number of units moved up or down. The change in
, or the run, is the number of units moved to the right or left. Slope is found by dividing the vertical change (the change in
) by the horizontal change (the change in
). In other words, the slope of a straight line is found by dividing the rise by the run, often described as rise over run.
Linear and Nonlinear Graphs
The lines on a graph can help you draw conclusions about your data. The slope of a str
aight line shows how much one factor (
) changes in relation to another factor (
). A straight line shows that a regular linear relationship exists between the factors you are studying.
always changes the same amount in relation to
. Many relationships that scientists study are not linear. In a nonlinear graph, each unit changes in one factor (
) do not always bring the same change in another factor (
). The graph of this relationship will be a curve instead of a straight line. There is a nonlinear relationship between the factors being studied.
Making a Graph
Data tables help you arrange data.
help you understand and use that data. Graphs make it easy to recognize trends and make predictions.
A graph has a horizontal (side to side)
-axis and a vertical (up and down)
-axis more often than not represents the independent variable in the data table. The
-axis more often than not represents the dependent variable. Each axis is labeled with the name of the variable that is represented.
Each axis has its own range. To find the range, subtract the smallest value of a single variable from the largest value of the same variable.
The next step is to decide the scale of the graph. Each axis has its own scale. The scale is the size that is used for each box or grid mark on the graph.
The data points need to be plotted now. We plot the data points by putting a dot on the graph for each pair of data in the data table. Every so often, a “line of best fit” is needed. A line of best fit is a smooth line that is drawn to “fit,” or to include, some but not all of the data points. The smooth line without sharp turns or sudden bends shows the pattern described by the data. The line of best fit in addition shows how the data varies from the pattern.
The very last step is to give the graph a name. The name helps people recognize what the graph describes. Scientists often include the independent and dependent variables in the name.
Finding a Missing Quanity
Force=Pressure x Area
Volume=Area x Height
is the factor that the experimenter changes.
-In an experiment, the mass of each 5 apples is measured. The results are 95 grams, 85 grams, 90 grams, 85 grams, and 100grams. Identify the mode.
-What is the value of the data point in the middle of a set of data when the data are arranged in order from smallest to largest?
-In a scientific investigation, the purpose of an experiment is to
Test a hypothesis
-A hypothesis is ___.
A possible answer to a question
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