Ch 2, Section 1 Description and Measurement Study Guide
A. Measurement—describes world using numbers
1. Types of measurement—distance, time, speed, volume, mass
2. Measurement can also help describe events.
B. Approximated measurement based on previous experience is __estimation__.
*Estimation can help you make a rough measurement of an object by guessing.
1. Estimation is useful when actual measurements are __not easily_ made.
2. Estimation can check that an answer is reasonable__.
3. When you estimate, you often use the word about.
C. Precision and accuracy
1. _Precision_—a description of how close measurements are to each other
* If four measurements of a flag pole indicate that it is 45.21 m high each time, these measurements have a high degree of precision.
* Precision describes how closely individual measurements agree with each other.
a. Used to discuss number of decimal places a measuring device can measure
b. Degree of Precision—today’s measuring devices are more precise.
2. Accuracy—comparison of measurement to actual value
When evaluating a newspaper delivery, a homeowner would be most concerned about the accuracy of the throws.
3. Precision and accuracy are important in many medical procedures.
4. Measurements can be rounded when precision is not needed.
* 11.85 seconds rounded to the nearest second is 12 seconds.
5. Significant digits—reflect true precision of a calculation
* The number of digits that reflect the precision of a calculation are called significant digits or significant figures.
a. Multiplication or division—measurement with the fewest digits determines the number
of significant digits.
b. Addition or subtraction—significance determined to the place value of the least precise measurement
•Section 2 SI Units Study Guide
•A. The International System—SIunits, in multiples of ten, provide a standard of consistent measurement for global science, business, and industry.
•* The International System of Units established to facilitate the sharing of measurement data among people from every country
•B. Length—the distance between two points; SI unit—meter example: 0.01 meters are in a centimeter
•1. Measure pencil—use centimeters
•2. Measure distance from New York to Chicago—use kilometers
•C. Volume—amount of space an object takes up; SI unit—cubic meter
Example: *A 2-L container can hold 2000 cubic centimeters of liquid.
•1. To find volume of regular shape—measure length, width, and height and multiply
•* The amount of space an object occupies is its volume.
•2. To find volume of irregular shape—volume by immersion
•D. Mass—amount of matter in an object; SI unit—kilogram
*example: An object's mass depends only on the amount of matter in the object.
*Example: 0.001 grams are in a milligram
•E. Weight—measurement of force; SI unit—newton
•F. Temperature—measure of kinetic energy in particles of matter; SI unit—kelvin
* At sea level, water boils at 373 degrees Kelvin or 100 degrees Celsius.
*45°C = 318 degrees Kelvin
•G. Time—interval between two events; SI unit—second
•H. Rate—amount of change of one measurement in a given amount of time
Section 3 Drawings, Tables, and Graphs
A. Scientific Illustrations—often make information more clear than written text
can.
1. Drawings—can emphasize only necessary details or show things you can’t see. A good way to illustrate the flow of electricity through a wire is with a drawing.
2. Photographs—show an object exactly as it is at a single moment
B. Tables—display information in rows and columns for easier comprehension
The advantage that a data table has over data presented in a paragraph is that the way the data is organized makes it easier to compare things in the table.
C. Graphs—collect, organize, and summarize data visually A graph is used to
organize and summarize data in a visual way.
1. Line graph—shows relationship between twovariables, which must be numbers
2. Bar graph—uses bars of different sizes to show relationships between variables; one variable is divided into parts; the other variable is a number
3. Circle graph—shows parts of a whole as percentages. Always based on 100%.
4. Scales on graphs must be carefully constructed and analyzed so users easily understand the information.
*A ratio of two different measures is called a rate.