The Work of Scientists Measurement–A Common Language Mathematics and Science Graphs in Science Safety in the Science Laboratory Table of Contents

The Work of Scientists

Measurement–A Common Language

Mathematics and Science

Graphs in Science

Safety in the Science Laboratory

Table of Contents


A Standard Measurement System Using SI as the standard system of measurement allows scientists to compare data and communicate with each other about their results. SI units are based on multiples of 10.

- Measurement–A Common Language


Length The basic unit of length in the SI system is the meter (m).



Mass The basic unit of mass in the SI system is the kilogram (kg).



Volume Volume is the amount of space an object takes up.



Density

Because density is actually made up of two other measurements–mass and volume–an object’s density is expressed as a combination of two units.



Calculating Density Suppose that a metal object has a mass of 57 g and a volume of 21 cm3. Calculate its density.

Read and Understand

What information are you given?

Mass of metal object = 57 g

Volume of metal object = 21 cm3




Plan and Solve

What quantity are you trying to calculate?

The density of the metal object = __

What formula contains the given quantities and the unknown quantity?

Density = Mass/Volume

Perform the calculation.

Density = Mass/Volume = 57 g/21 cm3 = 2.7 g/cm3




Look Back and Check

Does your answer make sense?The answer tells you that the metal object has a density of 2.7 g/cm3. The answer makes sense because it is the same as the density of a known metal–aluminum.



Calculating Density

Practice Problem

What is the density of a wood block with a volume of125 cm3 and a mass of 57 g?

0.46 g/cm3



Calculating Density

Practice Problem

What is the density of a liquid with a mass of 45 g and a volume of 48 mL?

0.94 g/mL



Time The second (s) is the SI unit to measure time.



Temperature

In addition to the Celsius scale, scientists sometime use another temperature scale, called the Kelvin scale. The kelvin (K) is the official SI unit for temperature.



Converting Between Units

Using the appropriate conversion factor, you can easily convert one unit of measurement to another.

This example shows how to convert 1.5 kilometers to meters.



Comparing and ContrastingAs you read, compare and contrast different types of measurement by completing a table like the one below.


Characteristic Length Mass Time Temperature

Definition

SI Unit

Measuring Tool

Distance from one point to another

Amount of matter

Passing of events

Hotness or coldness

Meter (m) Gram (g) Second (s)Degrees of Celsius or Kelvin

Metric ruler Balance Watch or clock Thermometer


More on Measurement

Click the PHSchool.com button for an activityabout measurement.



End of Section:Measurement–

A Common Language


Area The area of a surface is the amount of space it covers. To find the area, multiply its length by its width. Remember to multiply the units as well.

Area = Length x Width

Suppose an area measures 12.0 m by 11.0 m.

Area = 12.0 m x 11.0 m = 132 m2

Practice Problem

Calculate the area of room 4.0 m long and 3.0 m wide.

4.0 m x 3.0 m = 12 m2

- Mathematics and Science


Area The area of a surface is the amount of space it covers. To find the area, multiply its length by its width. Remember to multiply the units as well.

Area = Length x Width

Suppose an area measures 12.0 m by 11.0 m.

Area = 12.0 m x 11.0 m = 132 m2

Practice Problem

Calculate the area of a ticket stub 5.1 mm long and2.62 mm wide.

5.1 mm x 2.62 mm = 13.4 mm2 (13, to the correct significant figure)



Accuracy and Precision In order to hit the bull’s-eye consistently, you need both accuracy and precision.



Significant Figures

The significant figures in a measurement include all of the digits that have been measured exactly, plus one digit whose value has been estimated.



Significant FiguresWhen you multiply measurements, your answer can only have the same number of significant figures as the measurement with the fewest significant figures.



Percent Error

Read and Understand

What information are you given?

Experimental value = 9.37 g/cm3

True value = 8.92 g/cm3


You calculate the density of an object to be 9.37 g/cm3. The density of the object is actually 8.92 g/cm3. Calculate your percent error.


Percent Error You calculate the density of an object to be 9.37 g/cm3. The density of the object is actually 8.92 g/cm3. Calculate your percent error.

Plan and Solve

What quantity are you trying to calculate?

Percent error = __

What formula contains the given quantities and the unknown quantity?



Percent Error

Plan and Solve

Perform the calculation.

Percent Error = 5.04%




Percent Error

Look Back and Check

The answer tells you that your percent error is about 5%. This answer makes sense because the experimental value and the true value were close to each other.




Percent Error

Tanya measured the mass of an object to be 187 g. Sam measured the object’s mass to be 145 g. The object’s actual mass was 170 g.

What is Tanya’s percent error?

10.0%



Percent Error

Tanya measured the mass of an object to be 187 g. Sam measured the object’s mass to be 145 g. The object’s actual mass was 170 g.

What is Sam’s percent error?

14.7%



Mean, Median, and Mode The mean is the numerical average of the numbers in a list.



Mean, Median, and Mode

If an ordered list has an odd number of entries, the median is the middle number in a set of data. If a list has an even number of entries, the median is the sum of the two middle numbers divided by two.



Mean, Median, and Mode

The mode is the number that appears most often in a list of numbers.



Before you read, preview the red headings. In a graphic organizer like the one below, ask a what, how, or why question for each heading. As you read, write the answers to your questions.

Asking Questions


What does estimation have to do with science?

Scientists use estimation when they cannot obtain exact measurements.

Accuracy refers to how close a measurement is to the true or accepted value, and precision refers to how close a group of measurements are to each other.

What are accuracy and precision?

The term significant figures refers to the digits in a measurement.

What are significant figures?

Percent error is a calculation used to determine how accurate an experimental value really is.

What is percent error?

They are ways to calculate an “average.”What are mean, median, and mode?

Questions Answers


Links on Math and Science

Click the SciLinks button for links on math and science.



End of Section:Mathematics and

Science


The Importance of Graphs Line graphs are used to display data to show how one variable changes in response to another variable. In this experiment, the responding variable is the time it takes for the water to boil. The manipulated variable is the volume of water in the pot.

- Graphs in Science


Plotting a Line Graph

- Graphs in Science


Plotting a Line Graph Activity

Click the Active Art button to open a browser window and access Active Art about plotting a line graph.

- Graphs in Science


Why Draw a Line of Best Fit? A line of best fit emphasizes the overall trend shown by all the data taken as a whole.

- Graphs in Science


Slope The slope of a graph line tells you how much y changes for every change in x.

- Graphs in Science


Car Travel

The graph shows the distance a car travels in a one-hour period. Use the graph to answer the questions that follow.

- Graphs in Science


Car Travel

Time (min), the manipulated variable, is plotted on the horizontal axis. Distance (km), the responding variable, is plotted on the vertical axis.

Reading Graphs:

What variable is plotted on the horizontal axis? What variable is plotted on the vertical axis?

- Graphs in Science


Car Travel

The car travels 10 km in10 minutes and 40 km in40 minutes.

Interpreting Data:

How far does the car travel in the first 10 minutes? In 40 minutes?

- Graphs in Science


Car Travel

The car is traveling 1 km per minute. It would travel 120 km in 120 minutes.

Predicting:

Use the graph to predict how far the car would travel in 120 minutes. Assume the car continues to travel at the same speed.

- Graphs in Science


Car Travel

The slope is 1 km/min. The slope provides information about the car’s average speed.

Calculating:

Calculate the slope of the graph. What information does the slope provide about the speed of Car 2?

- Graphs in Science


Car TravelDrawing Conclusions:

Compare the graphs for Car 1 and Car 2. What is the relationship between the steepness of the graph lines and the speed of the cars?

The slope of the graph for Car 1 is 0.5 km/min. Because the distance and time values are marked the same on the two graphs, a steeper line represents a greater speed. Car 2 is traveling twice as fast as Car 1.

- Graphs in Science


Using Graphs to Identify Trends Line graphs are powerful tools in science because they allow you to identify trends and make predictions.

- Graphs in Science


Building VocabularyA definition states the meaning of a word or phrase by telling about its most important feature or function. After you read the section, reread the paragraphs that contain definitions of Key Terms. Use all the information you have learned to write a definition of each Key Term in your own words.

- Graphs in Science

Key Terms: Examples:graph A graph is a picture of data that reveals patterns or

trends.

horizontal axis The horizontal axis is the graph line that runs from left to right.

vertical axis The vertical axis is the graph line that runs up and down.

origin The origin of a graph is the point where the horizontal and vertical axes meet.

Key Terms: Examples:coordinate

data point

line of best fit

linear graph

A coordinate is a point on a graph that is determined by a pair of numbers.

A data point on a graph is where an imaginary line from the horizontal axis would meet an imaginary line from the vertical axis.The line of best fit on a graph is a smooth line between points that reflects the general pattern of the points.

A linear graph is a straight-line graph.

Key Terms: Examples:slope

nonlinear graph

The slope of a graph line is how steep the line is.

A nonlinear graph is a graph on which the data points do not fall on a straight line.


End of Section:Graphs in Science

The Work of Scientists - Safety in the Science Laboratory

Safety in the Lab These safety symbols remind you to work carefully when performing labs in this textbook series. Make sure you are familiar with each safety symbol and what it means.


In Case of an Accident

When any accident occurs, no matter how minor, notify your teacher immediately. Then listen to your teacher’s directions and carry them out quickly.

- Safety in the Science Laboratory


OutliningAs you read, make an outline about science safety that you can use for review. Use the red headings for the main topics and the blue headings for supporting ideas.

Safety in the Science Laboratory

I. Safety in the LabA. Preparing for the LabB. Performing the LabC.End-of-Lab Procedures

II. Safety in the FieldIII.In Case of an Accident



Links on Laboratory Safety

Click the SciLinks button for links on laboratory safety.



End of Section:Safety in the

Science Laboratory


can be a

is is is

Average

Mean

The middle number

Graphic Organizer

The number that appears most often in a list of numbers

Median Mode

The numerical average


End of Section:Graphic Organizer

Documents

The Work of Scientists Measurement–A Common Language Mathematics and Science Graphs in Science Safety in the Science Laboratory Table of Contents