Chapter 1: The Nature of Science 

Section 1: The Methods of Science

• What is science?

  • Science is not just a subject in school. It is a method for studying the natural world.

  • Science covers many different topics that can be classified according to three main categories.

  • Life science deals with living things.

  • Earth science investigates Earth and space.

  • Physical science deals with matter and

    energy.

  • Scientific explanations help you understand the natural world.

  • As more is learned about the natural world, some of the earlier explanations might be found to be incomplete or new technology might provide more accurate answers.

  • Scientists learn new information about the natural world by performing investigations, which can be done many different ways.

  • Some investigations involve simply observing something that occurs and recording the observations, perhaps in a journal.

  • Other investigations involve setting up experiments that test the effect of one thing on another.

  • Some investigations involve building a model that resembles something in the natural world and then testing the model to see how it acts.

• Scientific Method: An organized set of investigation procedures

  • Many scientific investigations begin when someone observes an event in nature and wonders why or how it occurs.
  • Before testing a hypothesis, it is useful to learn as much as possible about the background of the problem.
  • Hypothesis: a possible explanation for a problem using what you know and what you observe.
  • Some hypotheses can be tested by making observations.
  • Others can be tested by building a model and relating it to real-life situations.
  • Experiment: tests the effect of one thing on another using controlled conditions.
  • Variable: a quantity that can have more than a single value.
  • Dependent Variable: value changes according to the changes in the other variables.
  • Independent Variable: variable you change to see how it will affect the dependent variable
  • Constant: A factor that does not change when other variables change
  • Control: the standard by which the test results can be compared.
  • An important part of every experiment includes recording observations and organizing the test data into easy-to- read tables and graphs.
  • When you are making and recording observations, you should include all results, even unexpected ones.
  • Interpreting the data and analyzing the observations is an important step.
  • If the data are not organized in a logical manner, wrong conclusions can be drawn.
  • An exciting and important part of investigating something is sharing your ideas with others.
  • Based on the analysis of your data, you decide whether or not your hypothesis is supported
  • For the hypothesis to be considered valid and widely accepted, the experiment must result in the exact same data every time it is repeated.
  • Scientists also should be careful to reduce bias in their experiments.
  • Bias: occurs when what the scientist expects changes how the results are viewed.
  • Scientists can lessen bias by running as many trials as possible and by keeping accurate notes of each observation made.
  • Valid experiments also must have data that are measurable.
  • Most importantly, the experiment must be repeatable.

• Visualizing with Models

  • Sometimes, scientists cannot see everything that they are testing.
  • Model: represents an idea, event, or object to help people better understand it.
  • Models have been used throughout history.
  • Today, many scientists use computers to build models.
  • Another type of model is a simulator.
  • Pilots and astronauts use flight simulators for training.

• Scientific Theories and Laws

  • Theory: an explanation of things or events based on knowledge gained from many observations and investigations.
  • If scientists repeat an investigation and the results always support the hypothesis, the hypothesis can be called a theory.
  • Scientific Law: a statement about what happens in nature and that seems to be true all the time.
  • Laws tell you what will happen under certain conditions, but they don’t explain why or how something happens.
  • A theory can be used to explain a law.

• The Limitations of Science

  • Science can help you explain many things about the world, but science cannot explain or solve everything.
  • Most questions about emotions and values are not scientific questions. They cannot be tested.
  • Science can’t answer all questions

• Using Science-Technology

  • Technology: the application of science to help people.
  • Technology doesn’t always follow science
  • One important historic example of science following technology is the development of the steam engine.
  • Science and technology do not always produce positive results.
  • Being more knowledgeable about science can help society address these issues as they arise.

Section 2: Standards of Measurement

• Units and Standards
  • Standard: an exact quantity that people agree to use to compare measurements.
  • Hands are a convenient measuring tool, but using them can lead to misunderstanding.
• Measurement Systems
  • For a measurement to make sense, it must include a number and a unit.
  • In 1960, an improved version of the metric system was devised. Known as the International System of Units, this system is often abbreviated SI, from the French Le Systeme Internationale d’Unites
  • The standard for mass, the kilogram, and other standards are kept at the International Bureau of Weights and Measures in Sèvres, France.
  • The SI system is easy to use because it is based on multiples of ten.
  • Prefixes are used with the names of the units to indicate what multiple of ten should be used with the units.
  • Sometimes quantities are measured using different units.
  • A conversion factor is a ratio that is equal to one and is used to change one unit to another.
  • To convert units, you multiply by the appropriate conversion factor.
• Measuring Distance
  • Metric rulers and meter sticks are used to measure length.
  • One meter is slightly longer than 1 yard and 100 m is slightly longer than a football field.
  • The size of the unit you measure with will depend on the size of the object being measured.
  • By choosing an appropriate unit, you avoid large- digit numbers and numbers with many decimal places.
• Measuring Volume
  • Volume: The amount of space occupied by an object
  • In measuring a liquid’s volume, you are indicating the capacity of the container that holds that amount of liquid.
  • The most common units for expressing liquid volumes are liters and milliliters.
• Measuring Matter
  • Mass: a measurement of the quantity of matter in an object.
  • The mass and volume of an object can be used to find the density of the material the object is made of.
  • Density: the mass per unit volume of a material.
  • You find density by dividing an object’s mass by the object’s volume.
  • The measurement unit for density, g/cm3, is a combination of SI units.
  • A unit obtained by combining different SI units is called a derived unit.
  • An SI unit multiplied by itself also is a derived unit.
• Measuring Time and Temperature
  • Time is the interval between two events.
  • The SI unit for time is the second.
  • Think of temperature as a measure of how hot or how cold something is.
  • For most scientific work, temperature is measured on the Celsius (C) scale.
  • On this scale, the freezing point of water is 0°C, and the boiling point of water is 100°C.
  • The SI unit of temperature is the kelvin (K). Zero on the Kelvin scale (0 K) is the coldest possible temperature, also known as absolute zero.
  • The temperature measurement you are probably most famil- iar with is the Fahrenheit scale, which was based roughly on the temperature of the human body, 98.6°.

Section 3: Communicating with Graphs

• A Visual Display
  • Scientists often graph the results of their experiments because they can detect patterns in the data easier in a graph than in a table.
  • Graph: a visual display of information or data.
  • Graphs are useful for displaying numerical information in business, science, sports, advertising, and many everyday situations.
  • Graphs make it easier to understand complex pat- terns by displaying data in a visual manner.
  • The conclusions drawn from graphs must be based on accurate information and reasonable scales.
• Line Graphs
  • A line graph can show any relationship where the dependent variable changes due to a change in the independent variable.
  • Line graphs often show how a relationship between variables changes over time.
  • You can show more than one event on the same graph as long as the relationship between the variables is identical.'
  • The most important factor in making a line graph is always using the x-axis for the independent variable. The y-axis always is used for the dependent variable.
  • Another factor in constructing a graph involves units of measurement.
  • Graphing calculators are valuable tools for making graphs.
• Bar Graphs
  • A bar graph is useful for comparing information collected by counting.
  • Uses for bar graphs include comparisons of oil, or crop productions, costs, or as data in promotional materials.
  • Each bar represents a quantity counted at a particular time, which should be stated on the graph.
  • As on a line graph, the independent variable is plotted on the x-axis and the dependent variable is plotted on the y-axis.
• Circle Graphs
  • A circle graph, or pie graph, is used to show how some fixed quantity is broken down into parts.
  • The circular pie represents the total.
  • The slices represent the parts and usually are represented as percentages of the total.
  • To create a circle graph, you start with the total of what you are analyzing.
  • When you use graphs, think carefully about the conclusions you can draw from them. You want to make sure your conclusions are based on accurate information and that you use scales that help make your graph easy to read.