Making and Reporting Measurements & Mass, Weight, Volume & Density

DIVE Science & Mathematics

Fall Semester 2022

Teacher: Ms. Wendy Writer

Email: no_reply@example.com

10TH GRADE \n CHEMISTRY

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Notes

  1. Making and reporting measurements

  • Accuracy and precision

  • Think of a target can be accurate on the bullseye but imprecise

  • If all the shots are close to each their precise

  • It is on the bullseye it is accurate

  • Percent Error

  • Percent Error is how we find accuracy

  • Formula: Actual - observed/ Actual * 100%

  • The most accurate you can be on a “graduated” cylinder is halfway a graduation

  • How precise can an instrument get me that results after multiple tries

  • Scientific Notation

  • If you move the decimal to the right you are going to get a number with a negative exponent

  • If you move the decimal to the left you are going to get a number with a positive exponent (Math in the notebook)

  • Significant Digits

  • Significant Digits tell us about the precision of an instrument. They are the “important” digits in a measurement

  • Instruments can be imprecise due to a variety of reasons humidity, electrical current, temperature

  • We can record values to the nearest tenth of a millimeter on a graduated cylinder  

  • On digital instruments, the number of displayed digits equals the number of significant digits

  • Rules for significant digits

  • significant digits apply ONLY to measurements

  • All nonzero measurements are significant

  • Zeros between nonsignificant digits are significant

  • All other zeros are significant unless they are placeholders

  • Placeholders hold the values of the number that come after it  

  • Example: 0.056 there are 2 significant digits vs

  • 2.30 there are 3 (placeholder vs no placeholder)

  • Use scientific notation to indicate the precision of the measurement

  • Addition/Subtraction: The answer cannot have more significant digits than the least precise measurement  

  • Mult/Division: The answer cannot contain more significant digits than the measurement with the least significant digits

  • Rounding: If the digit is dropped, then drop the digit; otherwise, increase the preceding digit by 1

  1. Mass, Weight, Volume & Density

  • Comparing Mass and weight

  • Mass is a measure of how much “stuff” an object contains

  • Weight is a measure of the effect of gravity on an object

  • You weigh more on Earth than on the moon

  • The Newton is the SI unit for weight measure

  • The gram is the base SI unit for mass and measure

  • On the earth, since gravity is pretty much the same everywhere, we use the words weight and mass interchangeably

  • English to SI units: 1 Netown = 0.225lb.

  • English units for weight and metric units for grams

  • Density

  • Density is the best unit for describing matter

  • Density = Mass/ Volume

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