Chapter 1: The Nature of Science

What is science? * Science is a method of studying the natural world * It is a process that uses observation and investigation to gain knowledge about events in nature
Major Categories of Science

Science Explains Nature * 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
Investigations * Scientists learn new information about the natural world by performing investigation, which can be done in different ways

Some investigation involve simply observing something that occurs and recording the observations, such as 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: organized set of investigation procedures that can include stating a problem, forming a hypothesis, researching and gathering information, testing a hypothesis, analyzing data, and drawing conclusions.

1. Hypothesis: a possible solution or an explanation that is consistent with what is known

1. Experiment: organized procedure for testing a hypothesis; tests the effect of one thing on another under controlled conditions.

Variables * Variable: factor that can cause a change in the results of an experiment. * Dependent Variable: factor that changes as a result of changes in the other variables. * Independent Variable: factor that, as it changes, affects the measure of another variable.

Constant: in an experiment, a variable that does not change when other variables change.

Control: standard used for comparison of test results in an experiment.

Being Objective * Scientists 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 may trials as possible and by keeping accurate notes of each observation made. * Experiments must be repeatable, findings are supportable when other scientists perform the same experiment and get the same results

Model: represents an idea, event, or object to help people better understand it.

High-Tech Models * Many scientist use computers to build models * Another type of model is a simulator
Scientific Theories and Laws * Theory: an explanation of things or events based on knowledge gained from many observations and investigations. * NOT a guess * A theory is achieved when an experiment is repeated and the results always supports the hypothesis * Theories can be modified * Scientific Law: a statement about what happens in nature and that seems to be true all the time. * Does not explain why or how something happens * A theory can be used to explain a law
Technology: the application of science to help people. * Science and technology are not the same * Technology does not always follow science * Science and technology do not always produce positive results

Standard: an exact quantity that people agree to use to compare measurements.

Precision: describes how closely measurements are to each other and how carefully measurements were made

Accuracy: compares a measurement to the real or accepted value.

International System of Units * SI Base Units * Quantity Measured: Length * Unit: meter * Symbol: m * Quantity Measured: Mass * Unit: kilogram * Symbol: kg * Quantity Measured: Time * Unit: second * Symbol: s * Quantity Measured: Electric current * Unit: ampere * Symbol: A * Quantity Measured: Temperature * Unit: kelvin * Symbol: K * Quantity Measured: Amount of substance * Unit: mole * Symbol: mol * Quality Measured: Intensity of light * Unit: candela * Symbol: cd * Common SI Prefixes * Prefix: Kilo- * Symbol: k * Multiplying Factor: 1,000 * Prefix: Deci- * Symbol: d * Multiplying Factor: 0.1 * Prefix: Centi- * Symbol: c * Multiplying Factor: 0.01 * Prefix: Milli- * Symbol: m * Multiplying Factor: 0.001 * Prefix: Nano- * Symbol: n * Multiplying Factor: 0.000 000 001
Converting Between SI Units * Conversion Factor: a ratio that is equal to one and is used to change one unit to another. * To convert units, multiply by the appropriate conversion factors * Use the conversion factor with new units in the numerator and the old units in the denominator
Choosing a Unit of Length * 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 number and numbers with many decimal places
Measuring Volume * Volume: the amount of space occupied by an object * Formula: (V = l x w x h)

Mass: a measurement of the quantity of matter in an object

Density: the mass per unit volume of a material.

Derived Units: a unit obtained by combining different SI units

A Visual Display * Graph: a visual display of information or data * Scientists often graph the results of their experiments because they can detect patterns in the data easier in a graph than in a table. * Graphs are useful for displaying numerical information in business, science, sports, advertising, and many everyday situations. * Different kinds of graphs—line, bar, and circle—are appropriate for displaying different types of information.
Line Graphs * A line graph can show any relationship where the dependent variable changes due to a change in the independent variable. * 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.
Bar Graphs * A bar graph is useful for comparing information collected by counting. * Each bar represents a quantity counted at a particular time, which should be stated on the graph.
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.