CHAPTER 1

INTRODUCTION TO SIENCE

SCIENCE

• The intellectual process using all available mental and physical resources to better understand, explain, quantitate, and predict normal as well as unusual natural phenomena

• The goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions

• Organized way of using evidence to learn about the natural world– Body of knowledge that has been built up over the

years

Scientific Method

• Observation

• Measurement

• Accumulation and analysis of verifiable data

Scientific Method

• Observation:– Process of gathering information about

events or processes in a careful, orderly way

– Generally involves using the senses, particularly sight, hearing, touch, smell, and taste

Scientific Method

• The information gathered from observations is called data– Observations and measurements that are made in an

experiment– There are two main categories of data:

• Quantitative data are expressed as numbers, obtained by counting or measuring

• Qualitative data are descriptive and involve characteristics that can't usually be counted:

– The researcher might make the qualitative observations that “the scar appears old” and “the animal seems healthy and alert.”

Inference

• Scientists may use data to make inferences

• Inference is a logical interpretation based on prior knowledge or experience– Example:

• Researcher might be testing water in a reservoir Because he/she cannot test all the water, he/she collects water samples from several different parts of the reservoir

– If all the samples are clean enough to drink, she may infer that all the water is safe to drink

Test Hypothesis

• Scientific hypotheses must be proposed in a way that enables them to be tested

• Some hypotheses are tested by performing controlled experiments, as you will learn in the next section

• Other hypotheses are tested by gathering more data:– In the case of the mystery illness, data would be collected by

studying the location of the event; by examining air, water, and food people were exposed to; and by questioning people about their actions before falling ill

• Some hypotheses would be ruled out• Others might be supported and eventually confirmed

Setting Up a Controlled Experiment 

• In science, testing a hypothesis often involves designing an experiment

• The factors in an experiment that can change are called variables– Examples of variables include:

• Equipment used• Type of material• Amount of material• Temperature• Light• Time

Setting Up a Controlled Experiment

• Suppose you want to know whether an increase in water, light, or fertilizer can speed up plant growth

• If you change all three variables at once, you will not be able to tell which variable is responsible for the observed results

• Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time

– All other variables should be kept unchanged, or controlled

– This type of experiment is called a controlled experiment

• The variable that is deliberately changed is called the manipulated variable

• The variable that is observed and that changes in response to the manipulated variable is called the responding variable.

• Problem: Car does not start!!!!!!

Theory

• You may have heard the word theory used in everyday conversations as people discuss ideas– Someone might say, “Oh, that's just a theory,” to

criticize an idea that is not supported by evidence

• In science, the word theory applies to a well-tested explanation that unifies a broad range of observations:– A theory enables scientists to make accurate

predictions about new situations

Theory

• A useful theory may become the dominant view among the majority of scientists, but no theory is considered absolute truth

• Scientists analyze, review, and critique the strengths and weaknesses of theories

• As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation:– Sometimes, scientists resist a new way of looking at

nature, but over time new evidence determines which ideas survive and which are replaced

– Thus, science is characterized by both continuity and change

Theory

• Theory: A system of ideas that explains many related observations and is supported by a large body of evidence acquired through scientific investigation

LAW

• LAW: A descriptive statement or equation that reliably predicts events under certain conditions– Newton’s laws of motion– Rectangle area equation (A=lxw)

– Universal gravitational equation (F=G m1m2/d2)

– Does not explain how a process takes place• In the example of the hot cooking pot, nothing in the law tells

why hot objects become cooler in cooler surroundings.• Such an explanation of how a natural process works must be

provided by a scientific theory.

Theory/Law

• Can these change????

METRIC SYSTEMSI BASE UNITS

• Prefixes are multiples of 10

Metric

• POWER DECIMAL• OF TEN EQUIVALENT PREFIX SUFFIX SYMBOL•  • 1012 1,000,000,000,000 tera T• 109 1,000,000,000 giga

G• 106 1,000,000 mega M • 103 1,000 kilo k• 102 100 hecto h• 10 10 deka da• 1 meter/liter/gram m/l/g

Metric

• POWER DECIMAL PREFIX SUFFIX SYMBOL• OF TEN EQUIVALENT• 1 meter/liter/gram m/l/g• 10-1 0.1 deci d• 10-2 0.01 centi

c• 10-3 0.001 milli m• 10-6 0.000 001 micro u• 10-9 0.000 000 001 nano n• 10-12 0.000 000 000 001 pico p• 10-15 0.000 000 000 000 001 femto f• 10-18 0.000 000 000 000 000 001atto a• ** to express the units you combine the prefix and suffix

Metric

• DIMENSIONAL ANALYSIS• Now that you know the basic units of the

metric/SI system, it is important that you understand how to go from one unit to another. The skill of converting one unit to another is called dimensional analysis

• Dimensional analysis involves determining in what units a problem is given, in what units the answer should be, and the factor to be used to make the conversion from one unit to another (RATIO OF UNITS).

Metric

• To perform dimensional analysis, you must use a conversion factor

• A conversion factor is a fraction that equal 1. • Example: Ratio of Units

• 1 kilometer equals 1000 meters• So the fraction 1 kilometer / 1000 meters equals 1

– So does the fraction 1000 meters / 1 kilometer

– The top number in a fraction is called the numerator

– The bottom number in a fraction is called the denominator

– In a conversion fraction the numerator always equals the denominator so that the fraction always equals 1

Metric

• Let’s see how dimensional analysis works. Suppose you are told to convert 2500 grams to kilograms. This means that grams are your given unit and you must express your answer in kilograms. The conversion factor you choose must contain a relationship between grams and kilograms that has a value of 1. You have two possible choices: Ratio of Units

• 1000 grams / 1 kilogram = 1• or• 1 kilogram / 1000 grams = 1 • To convert one metric unit to another, you must multiply the

given value times the conversion factor. Remember that multiplying a number by 1 does not change the value of the number. So multiplying by a conversion factor does not change the value, just the units.

Metric

• Now, which conversion factor should you use to change 2500 grams into kilograms? Since you are going to multiply by the conversion factor, you want the unit to be converted to cancel out during the multiplication. This is just what will happen if the denominator of the conversion factor has the same units as the value you wish to convert. Since you are converting grams into kilograms, the denominator of the conversion factor must be in grams and the numerator in kilograms. The first step in dimensional analysis, then, is to write out the value given, the correct conversion factor, and a multiplication symbol between them:

Metric

• 2500 grams X 1 kilogram / 1000 grams = • The next step is to cancel out the same

units: • 2500 X 1 kilogram / 1000 = • The last step is to multiply: 

• 2500 kilograms / 1000

•   2500 kilograms / 1000 = 2.5 kilograms

Metric• MASS VALUES:• 1 kilogram (kg) = 1,000 grams (g)• 1 hectogram (hg) = 100 grams (g)• 1 dekagram (dag) = 10 grams (g)• 1 gram (g) = 1 gram (g)• 1 decigram (dg) = 0.1 gram (g)• 1 gram (g) = 10 decigram (dg)• 1 centigram (cg) = 0.01 gram (g)• 1 gram (g) = 100 centigram (cg)• 1 milligram (mg) = 0.001 gram (g)• 1 gram (g) = 1000 milligram (mg)• 1 microgram (ug) = 0.000001 gram (g)• 1 gram (g) = 1,000,000 microgram (ug)• 1 nanogram (ng) = 0.000000001 gram (g)• 1 gram (g) = 1,000,000,000 nanogram (ng)

Metric• LIQUID VALUES:• 1 kiloliter (kl) = 1,000 liters (l)• 1 hectoliter (hl) = 100 liters (l)• 1 dekaliter (dal) = 10 liters (l)• 1 liter (l) = 1 liter (l)• 1 deciliter (dl) = 0.1 liter (l)

– 1 liter (l) = 10 deciliter (dl)• 1 centiliter (cl) = 0.01 liter (l)

– 1 liter (l) = 100 centiliter (cl)• 1 milliliter (ml) = 0.001 liter (l)

– 1 liter (l) = 1000 milliliter (ml)• 1 microliter (ul) = 0.000001 (l)

– 1 liter (l) = 1,000,000 microliter (ul)• 1 nanoliter (nl) = 0.000000001 (l)

– 1 liter (l) = 1,000,000,000 nanoliter (nl)

Metric• LENGTH VALUES:• 1kilometer (km) = 1,000 meters (m)• 1hectometer (hm) = 100 meters (m)• 1dekameter (dam) = 10 meters (m)• 1meter(m) = 1 meter (m)• 1decimeter (dm) = 0.1 meter (m)

1meter (m) = 10 decimeter (dm)• 1centimeter (cm) = 0.01 meter (m)• 1meter (m) = 100 centimeter (cm)• 1millimeter (mm) = 0.001 meter (m)• 1meter (m) = 1000 millimeter (mm)• 1micrometer (um) = 0.000001 meter (m)

1meter (m) = 1,000,000 micrometer (um)• 1nanometer (nm) = 0.000000001 meter (m)• 1meter (m) = 1,000,000,000 nanometer (nm) 

Metric

• Do the following conversions for homework. All work and individual steps MUST be shown !

• *** as you will see later the volume measurement of 1 ml is equivalent to 1 cubic centimeter or 1 cc or 1 cm 3

Metric• CONVERSIONS:• 3 m = _______ cm 3 m x 100 cm / 1 m = _________ cm•  • 1,500 ml = ______ l 1,500 ml x 1 l / 1000 ml = ________ l•  • 0.015 g = _______ mg 0.015 g x 1000 mg / 1 g = _________ mg•  • 0.25 km = _______ m 0.25 km x 1000 m / 1 km = ________ m•  • 2.5 l = __________ ml 2.5 l x 1000 ml / 1 l = _________ ml•  • 2,750 mg = _______ g 2,750 mg x 1 g / 1000 mg = ________ g•  • 2 mm = _________ um 2mm x 1000 um / 1 mm = __________um

•  • 2 mm = _________ nm 2 mm x 1,000,000 nm / 1mm = ____________ nm

• 5.1 g = __________ mg 5.1 g x 1000 mg/1 g = ____________mg

• 500 ml = ________ l 500 ml x 1 l / 1000 ml = _________ l

GRAPHS

• Line: displays changes over time (data that changes continuously)– Example: change of the volume of gas over a period of time

• Time: Independent variable• Volume: dependent variable

• Bar: useful when you want to compare similar data for several individual items or events– Example: if you measure the melting temperatures of various

metals

• Pie: ideal for displaying data that are parts of a whole– Example: composition of a jacket

Scientific Notation

• Reduces the size of very large/small numbers– Example:

• 5,250,000,000• 0.0000000062

Scientific Notation

• To reduce the number of zeros in very big and very small numbers, you can express the values as simple numbers multiplied by a power of 10

• Example:– 1,000 = 1.0 x 103

– 100 = 1.0 x 102

– 10 = 1.0 x 101

– 1 = 1.0 x 100

– 0.1 = 1.0 x 10-1

– 0.01 = 1.0 x 10-2

– 0.001 = 1.0 x 10-3

Scientific Notation

• Examples:

• 4,500,000,000,000 = 4.5 x 1012

• 0.000000000012 = 1.2 x 10-11

Scientific Notation

• When using scientific notation in calculations, you should follow the math rules for powers of 10.– When multiplying two values, you add the

powers of 10– When dividing two values, you subtract the

powers of 10

Scientific Notation

• (5.5 x 104cm) x (1.4 x 103cm) =

• (5.5 x 1.4)(104+3)(cmxcm)

• 7.7 x 107cm2

Scientific Notation

• 5.2 x 108cm3 / 9.5 x 102cm =

• (5.2 / 9.5) (108-2) (cm3-1)

• 0.547368421 x 106cm2

• 5.5 x 105cm2

Significant Figures

• A prescribed decimal place that determines the amount of rounding off to be done based on the precision of the measurement– The answer should have the same number of

significant figures as the least precise value in the calculation

• Example: 8.871m x 9.14m = 81.08094m2

– In this case, the value of 9.14 has three significant figures, so the correct rounded answer is 81.1 m2