Lab 01 Scientific Method, Metrics, Graphing 1 PDF

Preview

Summary

Download Lab 01 Scientific Method, Metrics, Graphing 1 PDF

Description

Name: _______________________________________

Section Number: ____________

Lab Partners: _______________________________________________________________________________

Introduction to the Scientific Method, Metric System, and Graphing of Data Prelab Read Safety handout. Print and bring this handout to lab. Read all materials before attending the lab. Watch the graphing video1 to learn what types of graphs are used for different kinds of data (this is a 10 minute video and is required viewing). Be sure to be on time, which means in the laboratory, seated, and ready to work at the top of the hour.

Safety Note

There are no safety precautions for this lab. However, ALWAYS be sure and pay specific attention to this symbol for each lab exercise. Different precautions will be listed depending upon what procedures are being performed each week. It is your responsibility to know in advance what to be aware of and how to dispose of any materials or chemicals being used.

Lab Purpose      

Learn the process of the Scientific Method Become familiar with metric units used to measure length, volume, mass and temperature. Convert from one metric unit to another. Become familiar with analysis of data through graphing Learn which type of graph to use depending upon data collected Be able to define the following terms: ac accur cur curacy acy acy,, pr preci eci ecisi si sion on on,, sci scien en entif tif tific ic me method thod thod,, o ob bser servat vat vation ion ion,, h hyp yp ypoth oth othesi esi esiss, vari variabl abl able, e, dep depen en ende de dent nt varia ariabl bl ble, e, iinde nde ndepe pe pend nd nden en entt vvaria aria ariabl bl ble, e, con contro tro trolle lle lled d ex expe pe peri ri rime me ment, nt, ba barr gr graaph, lin line e grap graph, h, pie ch chart art art,, sca scatter tter pl plot, ot, b best est fit lline ine

1 https://www.youtube.com/watch?v=9BkbYeTC6Mo

1

Materials     

Graphing Guidelines handout Graphing Rules handout Metric ruler Calculator Demo: beaker, Erlenmeyer flask, graduated cylinder, volumetric flask

Overview In today’s lab you will be introduced to the Scientific Method, metric units of measure, and the process of graphing data. You will use these throughout the semester to make predictions, measure and gather data, and plot that data into a graph to better analyze and make conclusions from your experimental results. Scientists utilize the metric system when taking measurements in and out of the laboratory. The measurements made in lab will most often be in grams (mass), liters (volume), meters (length), and degrees Celsius (temperature). Throughout the semester you will be taking measurements using different types of equipment for measuring these properties. In order for results to be meaningful, it is important to be able to recognize the accuracy and precision of the data collected. Accu ccuracy racy refers to how closely measured values agree with the true or correct value. Pre Precisi cisi cision on refers to how closely the measured values agree with each other. FIGURE 1 PRECISION VS . ACCURACY

To insure accuracy in your measurements, familiarity with equipment and its proper use is necessary. You will be introduced to lab equipment and its use in next week’s lab exercise.

Background Information Scientific Method The Sci Scient ent entific ific M Meth eth ethod od is a general term used for the steps used by the science community to investigate and make conclusions of questions about the natural world. Historically, the Scientific Method was described by the following specific steps:     

Make insightful observations Pose and clarify testable questions Formulate hypothesis Do experiments to gather data Make conclusions based on observed data

2

Obs Obser er ervati vati vation on onss may be independent and original, or they may be observations about research being done by other scientists. These observations lead to questions to be answered. These questions must then stated in the form of a hypo hypoth th thes es esis is is. A hypothesis is a statement that clearly defines the specifics of the experimental variables being tested. A hypothesis must be testable in such a way that the statement is supported or disproved. A hypothesis is never proven true, but if supported and repeated time and time again by other individuals and independent laboratories it may eventually become accepted and supported by the scientific community. An example would be the cell theory, which states that all living cells come from pre-existing cells. Up to this time, there has been no evidence to disprove this theory. In a scientific experiment, usually only one condition or va variab riab riable le is being changed or manipulated at a time. This is called the in indep dep depen en ende de dent nt var variiabl able. e. The dep dependen enden endentt vvari ari ariab ab able le is the factor being measured that is predicted to be affected by manipulation of the independent variable. In this way, one can assume that any change is due to the independent variable. FIG IGU URE 2 STE PS O OFF TTH H E SCI CIEN EN ENT TI FI FIC C M E TH THO OD

3

A more flexible, realistic model is emerging. This is illustrated using a more circular model which shows the Scientific Method as an ongoing process of revision, collaboration, and peer review. FIG IGU URE 3 H O W S CI CIE E NC NCE E WOR ORKS KS

The Metric System Basic Metric Units Scientific measurements are made in SI units (International System of Units)        

Length – meters (m) Volume – liters (L) Mass – grams (g) (kilogram is actual SI base unit) Temperature – kelvin (K) [similar to degrees Celsius (0C)] Time – seconds (s) Electric current – ampere (A) Luminous intensity – candela (cd) Amount of substance – mole (mol)

Metric Conversions The metric system is based on units of ten. Conversions within the metric system are a simple matter of moving the decimal point. We will learn how to convert. Base unit Meters or grams or liters, etc. there are no prefixes. Prefixes Add the prefix to the base unit to get the most appropriate range of measure.

4

TA BL BLE E 1 M E TR TRII C PR EF EFII XE XESS

Pref Prefix ix Sym Symbo bo boll Exp Expon on onenti enti ential al For Form m 6 megaM 10 kilok 103 hectorh 102 dekada 101 base (n/a) 100 decid 10-1 centic 10-2 millim 10-3 microµ 10-6 nanon 10-9 picop 10-12 femtof 10-15 Example 1 Convert from a large unit to a smaller unit.

De Decim cim cimal al For Form m 1,000,000 1,000 100 10 1 0.1 0.01 0.001 0.000001 0.000000001 0.000000000001 0.000000000000001

0.301 km = _______ dm To convert from one unit of measure to another, determine the number of decimal places you will have by taking the difference between the powers of 10 of the units you are converting between. Kilo (k; 103) to deci (d; 10-1). There is a difference of +4 orders of magnitude [3 − (−1) = 4], therefore, move the decimal 4 places to the right. 0.3010 km = 3010 dm A kilometer is a large unit compared to a decimeter, therefore the number gets larger because there are 10,000 decimeters in a kilometer. Example 2 You can also covert from small units to larger units. 10592.7 µm = _______ cm Micro (µ; 10-6) to centi (c; 10-2) there is a difference of -4 orders of magnitude [−6 − (−2) = −4], therefore move the decimal 4 places to the left. 10592.7 µm = 1.05927 cm A micrometer is a small unit compared to a centimeter, therefore the number gets smaller because there are 10,000 micrometers in a centimeter. Example 3 750 nm = _______ dam Nano (n) 10-9 to deca (da) 101 there is a difference of -10 orders of magnitude, therefore move the decimal 10 places to the left.. 750 nm = 0.0000000750 dam A nanometer is a very small unit compared to a decameter, therefore the number gets much smaller. 5

Complete the conversion problems below. 1. 2345 µL = ________________________ L

2. 56.78 mm = ______________________ nm

3. 1.40 kg = _______________________ cg

4. 0.000345 µg = _____________________ ng

5. 1.5 L = ______________________ mL

Laboratory Equipment: Volume Your instructor will show you 4 containers that are all used to hold liquid in the lab. Rank your prediction of the order of volume capacity of each piece of equipment from greatest to least capacity. The instructor will then show you the capacity of each and explain the differences in purpose of each piece of equipment. Record these in Table 2. T ABLE 2 V OLUME LAB E QUIPMENT Rank 1

Equipment name

Purpose

2 3 4

Graphing Data is collected in all disciplines of study, whether it is business, education, or science. Once data has been collected, the next step is the presentation of the information in a precise and clear manner. In some cases a table is all that is needed to convey the information to the reader. However, often times there is too much data to present this way, or patterns cannot be easily discerned from numbers on a page. Graphs are a very visual way to indicate relationships, trends, or comparisons of groups of data. Some things to consider when setting up a graph: 1. Know what point you are trying to make – comparison of two numbers, change over time, etc. 2. Know your options – linear graph, bar graph, histogram, pie chart 3. Know your audience – keep it simple, make it clear, and LABEL EVERYTHING Watch the graphing video1 to learn what types of graphs are used for different kinds of data (this is a 10 minute video and is required viewing). 1 https://www.youtube.com/watch?v=9BkbYeTC6Mo 6

Examples A line graph (also, line chart) is usually used to show data or information that changes continuously over time. Data points are plotted, and straight lines are used to connect each data point. This is different from the “best fit” straight line that goes through a set of many data points in a scatter plot. FIGURE 4 LINE GRAPH

A scatter plot (also, scatter graph, scatter chart) shows the relationship between two sets of data . If there is a correlation between the two sets, a best fit line (also, best fit curve, trend line) can be drawn from the data and may pass through all of the points, some of the points, or none of the points. Best fit lines can be linear or curved, depending on the relationship between the data. The best fit line can then be used to determine an unknown value based upon a measured value of the other parameter.

FIGURE 5 S CATTER PLOT WITH A BEST FIT LINE (S TRAIGHT )

FIGURE 6 S CATTER PLOT WITH A BEST FIT LINE (C URVED)

7

A bar graph (also, bar chart ) compares something between different groups. These are especially useful for the groups do not have a measurement that can be plotted, but can be divided into different types or categories. A pie graph (also, pie chart) shows proportions of a whole.

FIGURE 7 BAR GRAPH

FIGURE 8 PIE C HART

Experimental data Below are three different experiments with data in table form. 1. Read the paragraph describing each data set, and stat tate e a hy hypot pot pothe he hesis sis be befor for fore e look lookin in ingg aatt th the e aactu ctu ctual al dat dataa. 2. Look at the data and dete eterm rm rmin in ine e th the e iind nd ndepe epe epend nd nden en entt aand nd d dep ep epend end enden en entt vvari ari ariabl abl ables es es. 3. Gr Grap ap aph h eeac ac ach h sset et o off d dat at ataa using the appropriate type of graph (bar graph, line graph, scatter graph, pie chart) following the information from the Graphing Guidelines and Graphing Rules handouts.  Be sure to specify units on both axes  Calculate appropriate divisions to maximize the use of the entire graph  Give your graph an appropriate title  Four pages of graph paper are included in this handout. Graph each set of data on a separate graph so you can maximize your graph size (one extra graph paper is included in case you make a mistake) 4. After graphing the data, sta state te th the e co concl ncl nclusio usio usion n yo you ud dete ete eterm rm rmin in ined ed fro from m eac each h gr graph aph aph.

Data Set 1 A law professor wanted to determine if the amount of time students spend studying and preparing for exams has a noticeable effect on the scores earned. At the beginning of the exam, she asked students to write down how many days they spent in preparation. After scoring the exams, she compiled the data in the table below. Graph the results, and make a conclusion from the data collected. Hypothesis:

8

T ABLE 3 LAW S CHOOL CANDIDATES' PREP T IMES AND TEST S CORES

Can Candid did didat at ate e 1 2 3 4 5 6 7 8

Day Dayss Stud Studied ied 7 9 5 1 8 4 3 6

Scor Score e Ear Earne ne ned d 23 25 14 5 22 15 11 17

Independent variable: _____________________ Dependent variable: _____________________ Conclusion:

Data Set 2 A market analyst wanted to determine the busiest times of activity at a store. The analyst observed the store over the course of a day. The data is recorded in the table below. Graph the data, and state a conclusion based upon analysis of your graph. Hypothesis: T ABLE 4

Nu Numb mb mber er o off Peo People ple 2 5 10 22 15 5 4 4 3

Tim Time eo off D Day ay 10 am 11 am 12 pm 1 pm 2 pm 3 pm 4 pm 5 pm 6 pm

Independent variable: _____________________ Dependent variable: _____________________ Conclusion:

9

Data Set 3 For her science fair project, Stephanie wanted to know if there was a difference in preference of vegetables between 6th grade boys and girls. She asked 31 boys and 31 girls to pick with of the listed vegetables was their favorite. She then put her results in the table below. Hypothesis:

T ABLE 5

Favo Favorit rit rite eV Ve eget getabl abl ables es Broccoli Carrots Corn Peas Squash

Boys 2 6 10 8 5

Girl Girlss 5 7 8 5 6

Independent variable: _____________________ Dependent variable: _____________________ Conclusion:

10

11

12

13

14...