Chapter 1: Scientists’ Tools

Introductory Activity Think about the following questions:  What does “doing science” mean to you?  Who “does science”?  What do “scientists” do?  What do you think of when you hear about science or scientists?  What comes to mind when you hear about “chemistry” or “chemists”?  Do you think science plays an important role in your life? If yes, where do you see science in your world? If no, explain why not. Share your answers with a partner Share your answers as a class.

Chemistry is an Experimental Science This chapter will introduce the following tools that scientists use to “do chemistry”  Section 1.1: Scientific Processes  Section 1.2: Observations & Measurements  Section 1.3: Designing Labs  Section 1.4: Converting Units  Section 1.5: Significant digits  Section 1.6: Scientific Notation

Chemistry is an Experimental Science Common characteristics Although no one method, there are Careful observation s Accurate & precise measurements Design your own labs Unit conversions Significant digit rules Scientific Notation Are used when you include May require When using in calculations, follow May require using

Section 1.1—Doing Science

There is no “The Scientific Method” There is no 1 scientific method with “X” number of steps There are common processes that scientists use  Questioning & Observing  Gathering Data Experimentation Field Studies Long-term observations Surveys Literature reviews & more  Analyzing all the data  Using evidence & logic to draw conclusions  Communicating findings

Science is “loopy” Science is not a linear process…rather it is “loopy”…and it’s not just about experimentation …there are many pathways…even more than are shown here! Observations Questions Data gathering (experiment, literature research, field observations, long-term studies, etc.) Hypothesis Trend and pattern recognition Conclusion formation Communication & Validation Model Formation Product or technology formation

Two types of Experiments This text will predominantly use experimentation for data gathering Two types of experiments will be used:  To investigate relationships or effect How does volume affect pressure? How does reaction rate change with temperature?  To determine a specific value What is the value of the gas law constant? What is the concentration of that salt solution?

Variables Dependent VariableIndependent Variable Controlled by you You measure or observe Example: How does reaction rate change with temperatur e depends on

Variables Dependent VariableIndependent Variable Controlled by you You measure or observe Example: How does reaction rate change with temperatur e TemperatureReaction rate depends on

Variables Dependent VariableIndependent Variable Example: What is the concentratio n of that salt solution?

Variables Variables are not appropriate in specific value experiments Dependent VariableIndependent Variable Example: What is the concentratio n of that salt solution? Not appropriate

Constants It’s important to hold all variables other than the independent and dependent constant so that you can determine what actually caused the change! Constants Example: How does reaction rate change with temperatur e

Constants It’s important to hold all variables other than the independent and dependent constant so that you can determine what actually caused the change! Constants Concentrations of reactants Example: How does reaction rate change with temperatur e Volumes of reactants Method of determining rate of reaction And maybe you thought of some others!

Prediction versus Hypothesis They are different! HypothesisPrediction Just predicts Attempts to explain why you made that prediction Example: How does surface area affect reaction rate?

Prediction versus Hypothesis They are different! HypothesisPrediction Just predicts Attempts to explain why you made that prediction Example: How does surface area affect reaction rate? Reaction rate will increase as surface area increases Reaction rate will increase with surface area because more molecules can have successful collisions at the same time if more can come in contact with each other.

Predictions versus Hypothesis HypothesisPrediction Example: What is the concentratio n of that salt solution?

Predictions versus Hypothesis It is not appropriate to make a hypothesis or prediction in specific value experiments HypothesisPrediction Example: What is the concentratio n of that salt solution? Not appropriate—it would just be a random guess

Gathering Data Multiple trials help ensure that you’re results weren’t a one-time fluke! Precise—getting consistent data within experimental error Accurate—getting the “correct” or “accepted” answer consistently Example: Describe each group’s data as not precise, precise or accurate Correct value

Precise & Accurate Data Example: Describe each group’s data as not precise, precise or accurate Correct value Precise, but not accurate Precise & Accurate Not precise

Can you be accurate without precise? Correct value This group had one value that was almost right on…but can we say they were accurate?

Can you be accurate without precise? Correct value This group had one value that was almost right on…but can we say they were accurate? No…they weren’t consistently correct. It was by random chance that they had a result close to the correct answer.

Precise is consistent within experimental error. What does that mean? Every measurement has some error in it…we can’t measure things perfectly. You won’t get exactly identical results each time. “Within Experimental Error” Correct value You have to decide if the variance in your results is within acceptable experimental error

Scientists take into account all the evidence from the data gathering and draw logical conclusions Conclusions can support or not support earlier hypothesis Conclusions can lead to new hypothesis, which can lead to new investigations As evidence builds for conclusions, theories and laws can be formed. Drawing Conclusions

Theory versus Law Many people do not understand the difference between these two terms LawTheory Describes why something occurs Describes or predicts what happens (often mathematical) Example: The relationship between pressure and volume Cannot ever become

Theory versus Law Many people do not understand the difference between these two terms LawTheory Describes why something occurs Describes or predicts what happens (often mathematical) Example: The relationship between pressure and volume Kinetic Molecular Theory— as volume decreases, the frequency of collisions with the wall will increase & the collisions are the “pressure” Boyle’s Law: P 1 V 1 = P 2 V 2 Cannot ever become

Scientists share results with the scientific community to:  Validate findings (see if others have similar results)  Add to the pool of knowledge Scientists use many ways to do this:  Presentations and posters at conference  Articles in journals  Online collaboration & discussions  Collaboration between separate groups working on similar problems Communicating Results