1. Voc. Terms Accuracy Decimal system Metric system Precision
Chapter 4
Voc. Terms Accuracy Decimal system Metric system Precision

2. Measurement
Chapter 4

3. Scientific study, like cooking, relies on definite measurements
Scientific study, like cooking, relies on definite measurements. The very word science implies exactness. To obtain meaningful experimental results and to develop a procedure that can be duplicated, measurements must be both precise and accurate.

4. Accuracy and Precision
Two separate concepts.
Vital to successful measuring.
Ex. If you need 10 grams of salt, and the amount that you scale registered is 10 grams, then the measurement is considered accurate.

5. Precision –
Need more than one measurement
Compare the results.

7. A common language used all around the world for measurement.
The Metric System
A common language used all around the world for measurement.
Beverages are sold by the liter
Food labels indicate the mass in grams Your car has both miles and kilometers

9. Unit of measure is needed
Metric Units
Unit of measure is needed
English system
- unit measuring length = inches
Metric system
- unit measuring length = meter (m)
Gram (g) to measure mass
Liter (L) to measure volume

10. The metric system is based on the decimal system.
Metric Prefixes
The metric system is based on the decimal system.
Prefixes – used to indicate
Multiple or fraction of the base unit
Can be combined with any unit of measure

11. Can use kilometers to describe a large number of meters.
Prefixes
Kilo = 1000
-1000 meters =
1kilometer
-1000 grams =
1 kilogram
-1000 liters =
1 kiloliter

12. Measurements smaller than 1 meter
Prefixes – -Milli -Centi -Deci Describe fractions of a meter

13. Metric Prefixes (chart on page 63)
Meaning
Numerical Value
Unit Example
Relationship to Unit
Kilo (k)
Thousand
1000
Kilometer (km)
1 km = 1000
Deci (d)
Centi ©
Mili (m)
Tenth
Hundredth
Thousandth
0.1
0.01
0.001
Decimeter (dm)
Centimeter (cm)
Millimeter (mm)
10 dm = 1 m
100cm = 1m
1000mm = 1m

14. Measurement Visualizations
Comparing Systems
(Comparison Chart)
Metric Unit
Symbol
Measurement Visualizations
English Equivalent
Gram
Kilogram g kg
A little heavier than a paper clip
Almost nine sticks of butter
0.035 oz
2.2 lb
Meter
Kilometer
Decimeter
Centimeter
millimeter m km dm cm mm
From the floor to about the doorknob
About two-thirds of a mile
About the diameter of an average grapefruit
Length of a staple
Width of a dime
1.09 yards
0.62 miles
3.94 inches
0.39 inches
0.039 inches
Liter
militer L mL
Just over a quart of milk
A little less than ¼ teaspoon
1.057 quarts
0.03 fluid oz

15. Recording Metric Data Measure correctly
Report findings precisely and accurately
Scales on laboratory measuring devices vary
Ex: Beaker – markings
every 10 mL of volume
Graduated cylinder
marked to the
milliliter
Estimating

16. As you use the scales on laboratory equipment, make it a habit to estimate to one decimal place past the unit of measure marked on the scale.
Ex. suppose you’re using a 100-ml graduated cylinder marked to whole milliliters, and the bottom of the meniscus is between 24 and 25 mL. You would report this as 24.3 mL or 24.8 mL, depending on how far above 24 mL the volume is.
Anyone who reads the data table will know that the last digit is just an estimate, but it will tell them whether the volume was closer to 24 mL or 25 mL.

17. Recording Final Zeros
the bottom of the meniscus is exactly on the 24-mL line
write 24.0 mL, it is clear that the volume is exactly 24 mL.
by recording the final zero, you report your data more precisely.

18. Measuring in Metric Measuring length Use a metric ruler or meter stick
Millimeters – smallest divisions on these tools
10 mm = 1 cm
Each mm line = 1/10 of a centimeter

20. Measuring Volume
Each container marked with a different scale
Resulting in varying degrees of accuracy

22. The Celsius Temperature Scale
100° separate freezing and
boiling points on the Celsius
scale
Fahrenheit scale, the
difference is 180°
Celsius degree represents
almost twice the temperature
changes as a Fahrenheit
degree.
Divided into 100 parts

23. Formulas for Converting Temperatures