The Nature of Science Chapter 1

The Nature of Science What is Science (as a discipline of study)? Science is a process to explain (and predict) natural phenomena. Questions that Cannot Be Answered (12:08) Scientific Method – Mythbusters TedTalk (7:32)

Branches of Science Biological – Living Things Physical – Matter and Energy Earth – Earth and Environs

The Nature of Science How do advancements in science happen? Through the Work of Others Circumstances Need (sonar) Accidentally (serendipity) Better Technology

The Nature of Science Technology - The application of scientific principles.

The Nature of Science Scientific Laws and Theories Fact - Measured constant. Some facts may be altered when re-tested with better instruments. Law - A repeatable event. A relationship that always occurs. Commonly, expressed as a mathematical relationship. Hypothesis - A predicted relationship. If test subjects ingest zinc tablets, then the frequency of viral infections will be less. Can be testable by direct experimentation. Theory - A well-tested explanation for why certain laws and facts exist. Belief - A statement that is not scientifically based in the same way as facts, laws, hypotheses or theories.

The Nature of Science Scientific Models Ideas that are use to explain No, Not This Kind! patterns observe in nature. Models are judged to be acceptable (or not) based on how well they can explain and predict data and how consistent they are with what is already known about the world.

The Nature of Science Scientific Models Different types of models: Physical Models Illustrative Models Conceptual Models Mathematical Models Computer Models Operational Models

The Nature of Science SCIENTIFIC METHOD: A procedure (process) for solving problems. –Problem Definition –Research –Hypothesis –Design/Conduct Exp. –Collect/Analyze Data –Conclusion Monty Python – Using The Nature of Science to Evaluate a Witch (5:30) The Times and Troubles of The Nature of Science (11:00)

The Nature of Science Problem Definition Scientists design experiments to answer questions or solve problems. A good problem statement may start as “How does _____ affect _____?”, or “What is the effect of _____ on ____?”.

The Nature of Science Variables – Factors that change during an experiment. –Independent (Manipulated) Variable - The factor that is being tested (changed). –Dependent (Responding) Variable – The result of the change.

The Nature of Science Variables The independent variable is almost always referred to first in the problem statement, and then the dependent variable. EX. What is the effect of caffeine of the growth of rodents?

The Nature of Science Constant Variables Potential variables in an experiment that are purposely kept constant.

The Nature of Science Experimental Control* A group of subjects or an experimental set-up that is not subject to the Independent (Manipulated) Variable (*Used for Comparison). Ex. What is the effect of overcrowding on the level of aggressive behavior of rats?

The Nature of Science Hypothesis A hypothesis is a prediction about the outcome of an experiment. Usually, a hypothesis is in the form of an If … then … statement. Ex. If the rodents are given caffeine, then their growth will be less.

The Nature of Science Material List A detailed list of materials used. Procedure The procedure is a step by step description of how to conduct your experiment and how the data will be collected.

The Nature of Science Data Collection / Presentation Measurement – 1. Qualitative – Subjective observations Temperature (hot, cold) Height (tall, short) 2. Quantitative – Measurable observations Temperature (21 o C) Height (1.62 meters)

The Nature of Science Quantitative Measurement - Le System International d’Unites (SI) a. Length – Linear measurement (meter) b. Mass – Amount of matter in an object (gram) c. Mole – Number of particles d. Temperature – Average molecular motion or average kinetic energy of the particles (Celsius, Kelvin). e. Time – Period between two events (seconds) ** In the metric system, Mass and Volume are related; 1 ml of water is equal to 1 cm 3 of water, which has a mass of 1 g.

The Nature of Science Converting in SI K H DU D C M kilo hecto deka base deci centi milli unit

The Nature of Science Derived Units of Measurement a. Area – Two-dimensional space (m 2 ) b. Volume – Amount of space occupied by matter. solid – m 3 (cm 3 ) liquid – liter (ml) c. Density – Mass of particles per volume [Mass/Volume] solid - (kg/m 3, g/cm 3 ) liquid – (kg/l, g/ml) d. Molar Mass (M) – Mass of particles per mole (g/mol) e. Concentration [c] – # of particle per volume (mol/liter) f. Energy (E) – Force applied over a distance (joule)

The Nature of Science Measurement Dimensional Analysis [Unit Conversions] Quantity Sought = Quantity Provided x Conversion Factor 12 Dollars = How many quarters? # of Quarters = 12 dollars x 4 quarters 1 dollar # of Quarters = 48 Quarters

The Nature of Science Accuracy and Precision Accuracy - How close the measurement is to the TRUE VALUE. Precision – How repeatable the measurement is.

The Nature of Science

Measurement Accuracy – Percent Error A means to compare a measured (experimental) value with a correct or accepted value. Percent Error = Value experimental – Value accepted x 100 Value accepted

The Nature of Science Accuracy – Sample Problem A student measures the mass and volume of a substance and calculated its density as 1.40 g/ml. The correct, or accepted, value of the density is 1.36 g/ml. What is the percent error of the student’s measurement? % Error = 1.36 g/ml – 1.40 g/ml x 100 = -2.9% 1.36 g/ml

The Nature of Science Measurement Precision – Significant Figures Some error or uncertainty always exists in any measurement. Measuring instruments provide a particular number of digits in a measurement. Significant Figures – All the digits in a measurement that are known with certainty plus one digit (which is uncertain).

The Nature of Science Significant Figures Indicates the level of accuracy of a measurement.

The Nature of Science Measurement Rules for Significant Figures – Non-zero digits are significant. Zeroes between non-zero digits are significant. Leading zeros are not significant. Trailing zeros are significant if preceded by a decimal.

The Nature of Science Measurement Significant Figures – Examples: 4.02 has 3 significant figures has 2 significant figures 5000 has 1 significant figure has 3 significant figures

The Nature of Science Measurement Scientific Notation – Used to express numbers that are very big or very small in a more simple way. value written as a simple number multiplied by a power of 10. Base number must include all non-zero numbers Only one digit goes in front of decimal Example: Base number is 2.5 Scientific notation = 2.5 x 10 6 Scientific Notation

The Nature of Science Measurement Adding and Subtracting w/ Sig. Figs – When adding or subtracting decimals, the answer must have the same number of digits to the right of the decimal point as there are in the measurement having the fewest digits to the right of the decimal point. Example: 25.1 g g = g Using significant figures, the answer is 27.1 g

The Nature of Science Measurement Multiplying & Dividing w/ Sig. Figs – When multiplying or dividing with decimals, the answer must have the same total amount of significant figures as the measurement with the fewest significant figures. Example: 5.75 m x 4.25 m x m = m 3 Using significant figures, the answer is 76.4 m 3

The Nature of Science Data Collection / Presentation Data Collection - –Data are precisely measured. –All measurements in metric units (liters, grams, meters). –Record your data as you measure. –Sample size/number of trials is appropriate.

The Nature of Science Data Collection / Presentation Data Table 2 Relationship between Temperature and Volume of a Gas Temperature Volume (ml) (C o ) Trial 1Trial 2Trial 3Avg.Range

The Nature of Science Data Collection / Presentation Number Title (that states the variables)

The Nature of Science Data Collection / Presentation Line graph – Shows relationship between continuous data.

The Nature of Science Data Collection / Presentation Double Line Graph

The Nature of Science Data Collection / Presentation Bar graph – Shows comparison between data.

The Nature of Science Data Collection / Presentation Pie Chart – Shows Proportions.

The Nature of Science

Analysis / Conclusions 1.Provide Background Information and State the purpose of your experiment. 2. Interpret the data. –Answer the PS. –Do not summarize 3. Provide a reason why the data supports or disproves your conclusion (research/notes may be needed). 4. Compare your results to your hypothesis. 5. Describe limitations in the design/performance of the experiment that may have affected the data. 6. Provide a discussion of improvements to experiment.