Measuring

Accuracy v. Precision pg. 8Precision - how closely the measurements match each other. Instruments that measure using more decimals are more precise.

Accuracy – how closely the measurement matches the true or accepted value.

Accurate Precise

Accurate Precise

Accurate Precise

Accurate Precise

Accurate Precise

How To Read Scientific Instruments

• 1) Record the _______ digit on the instrument.

• 2) Then _______________ the last digit.

Significant Figures• Measuring devices are not perfect.• Human measurements always have a

small degree of uncertainty• All digits known for certain plus the last

digit which is an estimation.• Each digit in the measurement is called a

significant figure.

How to Read a Graduated Cylinder

• Sit the graduated cylinder on a level surface.• Lower your eyes to the level of the liquid

(called the meniscus).• Take your reading from the bottom of the

meniscus.• Count all of the digits you are sure of.• Add the last digit that you estimate.

Quiz page13

• Number your paper 1 to 15.

1) Measuring Length

A. 2 cm B. 19 cmC. 1.95 cmD. 1.95238 cm

2) Measuring Length

A. 10cm

B. 1.1cmC. 1.05cmD. 1.526cm

3) Measuring Length

A. 17 cm B. 17.5 cmC. 18.0 cmD. 17.5082 cm

4) Measuring Length

A. 4cm

B. 4.3cmC. 4.30cmD. 4.3057cm

5) Measuring Length

A. 12 cm B. 12.0 cmC. 12.7 cmD. 12.0953 cm

6) Measuring Liquids• The meniscus is the curve in the upper

surface of a liquid close to the surface of the container or another object, caused by surface tension. It can be either convex or concave.

Is this meniscus convex or concave? 6) _________________

For questions 7 to 12, measure the amount of liquid in each graduated cylinder by reading the bottom of the meniscus.

7) Measuring Liquid Volume

A.10mlB.10.3mlC.11.5mlD.13.0ml

8) Measuring Liquid Volume

A. 266 mlB. 287 mlC. 290 mlD. 294 ml

9) Measuring Liquid Volume

A.52 mlB.53 mlC.54.5 mlD.52.8 ml

10) Measuring Liquid Volume

A.80 mlB.80.0 mlC.81.0 mlD.79.0 ml

11) Measuring Liquid Volume

A.2.8 mlB.2.80 mlC.2.90 mlD.2.9 ml

12) Choose the correct answer.Amelia measured the amount of liquid her thimble would hold. She wrote down three numbers: 4.4ml, 4.3ml and 4.5ml. Pick the letter that best describes her measurements based on the actual amount of liquid shown in the graduated cylinder.

A.AccurateB.PreciseC.Both Accurate and PreciseD.Neither Accurate nor Precise

13) Measuring Solids

A.625.62gB.26.57gC.265.73D.526.6g

14) Measuring Solids

A.373.33gB.734.33gC.374.33gD.373.3g

15) Measuring Solids

A.222.50gB.221.50gC.221.5gD.221.0g

Answers to Quiz1) C 1.95cm2) C 1.05cm3) B 17.5cm4) C 4.30cm5) B 12.0cm6) Concave7) C 11.5ml8) D 294ml9) D 52.8ml10) B 80.0ml11) B 2.80ml12) B Precise13) C 265.73g14) A 373.33g15) B 221.50g