Metric System, Measurements, Percent Error, and Scientific ...



Objectives:List the metric units for length, mass, and volume.Use the metric system for measurements.Convert units within the metric system.Convert temperatures from Celsius and Fahrenheit scales.Determine the densities of solid substances. Calculate the percent error of these measurements.Conduct a scientific experiment, using accepted methods of scientific inquiry.Materials:metric rulerpennydiedominomarblewooden dowelcalculatorbalancegraduated cylindermeter stickIntroduction:Earth science involves studying phenomena on many different scales – from atoms to galaxies. Almost every scientific investigation requires accurate measurements. To describe objects, Earth Scientists use units of measurement that are appropriate for the particular feature or phenomenon being studied. For example, they would use centimeters, instead of kilometers, to measure the width of this page; they would use kilometers, rather than centimeters, to measure the distance from New York to London, England. Most areas of science have developed units of measurement that meet their particular needs. The fundamental units have been established by the International System of Units (SI). The metric system is a decimal system that uses only one basic unit for each type of measurement: the meter (m) for length, the liter (l) for volume, and the gram (g) for mass.In the metric system, the basic units of weights and measures are related by multiples of ten. It is similar to the United States monetary system, where 10 pennies = 1 dime and 10 dimes = 1 dollar. The Table below lists the prefixes that are used in the metric system to indicate how many times more (in multiples of 10) or what fraction (in fractions of 10) of the basic unit is present. Therefore, from the information in the table, you can see that 1 kilogram (kg) = 1,000 grams, while 1 milligram (mg) = 1/1,000 gram.PrefixSymbolMeaningkilo-k1,000 times the base unithecto-h100 times the base unitdeka-da10 times the base unitm (meter) base unit of lengthBASE UNITl (liter) base unit of volumeg (gram) base unit of massdeci-done-tenth the base unit (.1 x base)centi-cone-hundredth the base unit (.01 x base)milli-mone-thousandth the base unit (.001 x base)To familiarize yourself with metric units, determine the following measurements, using the equipment provided in this investigation.Measuring Length:Use the meter stick to measure your height as accurately as possible to the nearest hundredth of a meter (called a centimeter). _______________ centimeters (cm)Use the metric ruler to measure the length (top to bottom) of this sheet of paper as accurately as possible to the nearest tenth of a centimeter (called a millimeter). _______________ millimeters (mm)Accurately measure the length of your shoe to the nearest millimeter. _______________ millimeters (mm)Measuring Volume:Volume is the amount of space an object takes up. The process of displacement is used to determine the volume of an irregular solid. When there is a regularly shaped object (sphere, cube, cylinder …) a formula is used to calculate volume.The former requires the use of a graduated cylinder and uses the units of milliliters (ml). Start by filling the graduated cylinder to a known level (let’s say the 10 ml mark). Next immerse the object into the water in the graduated cylinder. Note the new water level. The difference between the beginning and ending water levels is the volume of the object. Use the displacement method to measure the volume of the following to the nearest milliliter.marble____________ milliliters (ml)b. penny ____________ milliliters (ml)The later method to determine volume requires measuring with the metric ruler and then using the formulas listed on page 732 in your textbook. The unit for volume using this method is cubic centimeters (cm3).Determine the volume of the following to the nearest cubic centimeters (cm3).domino _____________ cubic centimeters (cm3) c. wooden dowel _____________ cubic centimeters (cm3)die _____________ cubic centimeters (cm3)Note: A millimeter (ml) is equal to a cubic centimeter (cm3).Measuring Mass:Mass the following and record your results.marble __________ grams (g)c. domino __________ grams (g)penny __________ grams (g)d. die __________ grams (g) e. wooden dowel __________ grams (g) Note: Two terms that are often confused are mass and weight. Mass is a measure of the amount of matter an object contains. Weight is a measure of the force of gravity on an object. For example, the mass of an object would be the same on both Earth and the Moon. However, because the gravitational force of the Moon (1.6 m/s2) is less than that of Earth (9.8 m/s2), the object would weigh less on the Moon.Metric Conversion:As stated earlier, one important advantage of the metric system is that it is based on multiples of ten. As shown on the metric conversion table below, conversion from one unit to another can be accomplished simply by moving the decimal point to the left if going to larger units or by moving the decimal point to the right if going to smaller units.For example, if you measure the length of a piece of string and find it is 1.43 decimeters long, in order to convert its length to millimeters, start with 1.43 on the “deci-“ step of the table. Then move the decimal two places (steps) to the right (the “milli-“ step). The length, in millimeters, is 143.0 millimeters.Use the conversion table above to convert the following:2.05 meters (m) = ___________ centimeters (cm) e. 6.8 meters (m) = ___________ kilometers (km)1.5 meters (m) = ___________ millimeters (mm) f.4,214.6 centimeters (cm) = ___________ meters (m)9.81 liters (l) = ___________ deciliters (dm) g.321.5 grams (g) = ___________ kilograms (kg)5.4 grams (g) = ___________ milligrams (mg) h.70.73 milliliters (mm) = ___________ deciliters (dl)Use the meter stick to determine the shortest width of the lab desk as accurately as possible. Then convert the length to each of the units in question 8b.shortest width of the lab desk _________________ meters (m)width of lab desk equals _________________ millimeters (mm) _________________ centimeters (cm) _________________ kilometers (km)Temperature:Temperature represents one relatively common example of using different systems of measurements. On the Fahrenheit temperature scale, 32 ℉ is the melting point of ice, and 212 ℉ marks the boiling point of water (at standard atmospheric pressure). On the Celsius scale, ice melts at 0 ℃ and water boils at 100 ℃.Conversion from one temperature scale to another can be accomplished using either an equation. To convert Celsius degrees to Fahrenheit degrees, the equation is ℉ = (1.8) ℃ + 32° . To convert Fahrenheit degrees to Celsius degrees, the equation is ℃ = (℉ – 32°)/1.8.Convert the following temperatures to their equivalents. On a cold day, it was 8 ℉ = ______________ ℃.e. Normal body temperature is 98.6 ℉ = ___________ ℃.Ice melts at 0 ℃ = _____________ ℉.f. A warm shower is 27 ℃ = ____________ ℉.Room temperature is 72 ℉ = ____________ ℃.g. Hot soup is 72 ℃ = ____________ ℉.A hot summer day was 35 ℃ = __________ ℉.Density:One important property of a material is its density. Density is the mass of a substance per unit volume, usually expressed in grams per cubic centimeter (g/cm3). Differences in densities of earth’s matter are the basics of many common processes. Wind, ocean currents, and plate tectonics are all driven by differences in density. A way to remember this formula is a heart symbol with a line dividing it into a top and bottom.3301476333651olume00olume3359426-939ass00ass2651760309162Calculate the density of the following objects used in questions #4 -6.marble __________ grams/mlpenny __________ grams/mldomino __________ grams/cm3die __________ grams/cm3wooden dowel __________ grams/cm3Percent Error:Even careful measurements contain some error. Percent error is the amount by which a measurement differs from an accepted value. In this investigation, you have determined the mass and volumes and then calculated the densities for the above 5 objects.Obtain the accepted value for the density of each of your objects from Mr. Benedict. Use this value to calculate the percent error for each object. Use the formula below. Record your results.Percent Error = calculated value - accepted value x 100accepted valuemarble __________ %b. penny __________ % c.domino __________ %d. die __________ %e. wooden dowel __________ %Methods of Scientific Inquiry:Scientists use many methods in attempting to understand natural phenomena. Some scientific discoveries represent purely theoretical ideas, and others occur by chance. However, scientific knowledge is often gained by following this sequence of steps:Step 1: Establish a hypothesis- a tentative, or untested, explanation Step 2: Gather data and conduct experiments to test the hypothesis.Step 3: Accept, modify, or reject the hypothesis, on the basis of extensive data gathering or experimentation. Observe all the people in the class and pay particular attention to each individual’s height and shoe length.Based on your observations, write a hypothesis that relates a person’s height to his or her shoe length.Hypothesis: _______________________________________________________________________________________________________________________________________________________________________________________________________________Previously, in questions 1 and 3 of the investigation, each person in class measured his or her height and shoe length.Gather your data by asking 10 people in class for their height and shoe length measurements. Enter your data in the data table below. Record the height to the nearest centimeter and shoe length to the nearest millimeter. Person Height (nearest centimeter) Shoe length (nearest millimeter)1 cm mm2 cm mm3 cm mm 4 cm mm5 cm mm6 cm mm7 cm mm8 cm mm9 cm mm10 cm mmEvaluate your hypothesis by plotting your data on the graph below. The person’s height on the Y-axis (vertical) and shoe length on the X-axis (horizontal). Place a dot on the graph for each person. Do not connect the dots!Height vs. Shoe Length-546252210185200 00200 -112764945719Height in centimeters 00Height in centimeters -541655226695150 00150 150 200 250 300 350Shoe length in millimetersDescribe the pattern of the data points (dots) on the height versus shoe length graph. For example, are the points scattered all over the graph, or do they appear to follow a line or curve ? ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Draw a single line on the graph that appears to average, or best fit, the pattern of the data points.Describe the relationship of height to shoe length that is illustrated by the line on your graph. ___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Ask several people, whose height and shoe length are not part of your data set. Then see how accurately your line predicts what their shoe length should be. Do this by marking each person’s height on the Y-axis and then follow a line straight across to the right until you intersect the line of best fit that you drew. Then go directly down to the X-axis to get their predicted shoe length.Summarize how accurately your graph predicts a person’s shoe length, given his or her height. __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Using your graph’s ability to make predictions as a guide, do you think you should accept, reject, or modify your original hypothesis ? Give reasons for your choice. _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Your study has been restricted to the people in your class. Why would your ability to make predictions have been more accurate if you had used the heights and shoe lengths of 10,000 people ? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Drawing hasty conclusions with limited data can often cause problems. In science, you can never have too much data. Experiments are reported many times by many different people before results are accepted by the scientific community. ................
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