Scientific MethodScientific Method

Unit 1AUnit 1A

ObservationObservation

Recognizing or Recognizing or noting facts about noting facts about a specific instancea specific instance

HypothesisHypothesis

Proposed & testable explanation of the Proposed & testable explanation of the observationobservation

Example: Example: Observation- When I hold my pen up and then Observation- When I hold my pen up and then

let go, it falls to the floorlet go, it falls to the floor Hypothesis- The floor and the pen are Hypothesis- The floor and the pen are

magnetically attracted to each other, therefore magnetically attracted to each other, therefore when the pen is free to move, it moves to the when the pen is free to move, it moves to the floor.floor.

ExperimentExperiment

A step by step, repeatable process for A step by step, repeatable process for testing a hypothesistesting a hypothesis Independent variable: what is being Independent variable: what is being

tested- YOU control this variable!tested- YOU control this variable! Dependent variable: what can change Dependent variable: what can change

when the independent variable is when the independent variable is changedchanged

Control: variable that remains the same Control: variable that remains the same throughout the experimentthroughout the experiment

Let’s try to identify the Let’s try to identify the variables…variables…

1 - Patty Power1 - Patty Power Mr. Krabbs wants to make Bikini Bottoms a nicer place to live. He Mr. Krabbs wants to make Bikini Bottoms a nicer place to live. He

has created a new sauce that he thinks will reduce the production of has created a new sauce that he thinks will reduce the production of body gas associated with eating crabby patties from the Krusty body gas associated with eating crabby patties from the Krusty Krab. He recruits 100 customers with a history of gas problems. He Krab. He recruits 100 customers with a history of gas problems. He has 50 of them (Group A) eat crabby patties with the new sauce. has 50 of them (Group A) eat crabby patties with the new sauce. The other 50 (Group B) eat crabby patties with sauce that looks just The other 50 (Group B) eat crabby patties with sauce that looks just like new sauce but is really just mixture of mayonnaise and food like new sauce but is really just mixture of mayonnaise and food coloring. Both groups were told that they were getting the sauce coloring. Both groups were told that they were getting the sauce that would reduce gas production. Two hours after eating the crabby that would reduce gas production. Two hours after eating the crabby patties, 30 customers in group A reported having fewer gas patties, 30 customers in group A reported having fewer gas problems and 8 customers in group B reported having fewer gas problems and 8 customers in group B reported having fewer gas problems.problems.

Which people are in the control group?Which people are in the control group? What is the independent variable?What is the independent variable? What is the dependent variable?What is the dependent variable?

DataData

Information gathered from an Information gathered from an experimentexperiment Quantitative data: numbers and Quantitative data: numbers and

measurementsmeasurements Qualitative data: describes the quality Qualitative data: describes the quality

Accurate or Precise DataAccurate or Precise Data

Accurate data Accurate data refers to how close refers to how close a set of data is to a set of data is to the correct or the correct or known value.known value.

Precise data refers Precise data refers to how close a set to how close a set of data points are of data points are to each other.to each other.

Accurate vs. Precise DataAccurate vs. Precise Data

Trial #Trial # Mass (g)Mass (g)

11 17.1017.10

22 15.0015.00

33 16.7616.76

44 15.0515.05

55 14.9814.98

66 15.9915.99

     

Known Value = 15.02 gKnown Value = 15.02 g

Error in the LabError in the Lab

Human error – can occur when a Human error – can occur when a person doesn’t measure substances person doesn’t measure substances correctly or makes a mathematical correctly or makes a mathematical error. error.

Error in the LabError in the Lab

Mechanical error – may be out of Mechanical error – may be out of your control. Sometimes equipment your control. Sometimes equipment may not be calibrated correctly or is may not be calibrated correctly or is broken without you knowing it and it broken without you knowing it and it measures incorrectly.measures incorrectly.

Data Analysis – Graphing Data Analysis – Graphing GuidelinesGuidelines

1. Always give your graph a title in 1. Always give your graph a title in the following form: “The Dependence the following form: “The Dependence of (your dependent variable) on (your of (your dependent variable) on (your independent variable)”.independent variable)”.

Ex. The Dependence of Reaction Rate on Ex. The Dependence of Reaction Rate on TemperatureTemperature

2. The x-axis of a 2. The x-axis of a graph is always the graph is always the independent independent variable & the y-variable & the y-axis is the axis is the dependent variable. dependent variable. Always label your x Always label your x and y axes and give and y axes and give units!units!

The Dependence of Reaction Rate on Temperature

0.00

0.50

1.00

1.50

2.00

0 50 100 150

Temperature (degrees Celsius)

Rea

ctio

n R

ate

(min

ute

s)

3. Always make a line graph!3. Always make a line graph!

Line graphs are better in science Line graphs are better in science because they tell you how one thing because they tell you how one thing changes under the influence of some changes under the influence of some other variable! other variable!

4. Never, EVER, connect the dots on your graph!4. Never, EVER, connect the dots on your graph!

Why? When you do an experiment, you always screw Why? When you do an experiment, you always screw something up. Yeah, you! It’s probably not a big mistake something up. Yeah, you! It’s probably not a big mistake and is, frequently, not something you have a lot of control and is, frequently, not something you have a lot of control over. However, things can and do go wrong. As a result, over. However, things can and do go wrong. As a result, experimental data never makes a nice, straight line. experimental data never makes a nice, straight line. Instead, it makes a bunch of dots that seem to wiggle Instead, it makes a bunch of dots that seem to wiggle around a graph. This is normal!around a graph. This is normal!

You’re best bet is to make a line or curve that follows the You’re best bet is to make a line or curve that follows the data as well as possible without actually connecting the data as well as possible without actually connecting the dots. This shows the trend in the data, without depending dots. This shows the trend in the data, without depending too much on the noise created by error. too much on the noise created by error.

5. Make sure your data is graphed as 5. Make sure your data is graphed as large as possible in the space you’ve large as possible in the space you’ve been given.been given.

Example of a Bad GraphExample of a Bad Graph

There's no title.  What's it a There's no title.  What's it a graph of?  Who knows? graph of?  Who knows?

There are no labels on the x There are no labels on the x or y axis.  What are those or y axis.  What are those numbers?  Who knows? numbers?  Who knows?

There are no units on the x or There are no units on the x or y axis.  Is this a graph of y axis.  Is this a graph of speed in miles per hour or a speed in miles per hour or a graph of temperature in graph of temperature in Kelvins?  Who can tell? Kelvins?  Who can tell?

Somebody played "connect Somebody played "connect the dots".  This should be a the dots".  This should be a nice straight line which goes nice straight line which goes through the points or a curve through the points or a curve that tends to follow them.that tends to follow them.

A Good Graph!A Good Graph!

Theory or Scientific LawTheory or Scientific Law

TheoryTheory Explains why Explains why

specific phenomena specific phenomena occuroccur

Scientific LawScientific Law Describes what Describes what

happens when the happens when the phenomena occurphenomena occur