Significant Figures Activity

Significant Figures Activity

Introduction

In science many of the numbers that we deal with are a direct result of measurements. When the measuring device, whether it be a ruler or a balance, is read, a number is recorded. This number contains one or more known digits and one estimated digit. These digits are referred to as significant figures. The number of significant figures usually depends upon the measuring device. For example, a centigram balance provides two decimal places while an analytical balance can be read to four.

Purpose

To measure a figure with rulers with different scales and to us these measurements to determine areas and volumes to the proper number of significant figures.

Equipment/Materials

rulers that measure cm and mm

Safety:

·  Goggle should be worn in the laboratory at all times.

Procedure

1. Using a ruler with only a centimeter scale, measure the figure below. Record the length and width. Indicate the number of significant figures in your measurement and circle the digit that was estimated.

Length:______Sig.Figs:______

Width:______Sig Figs:______

Area:______Sig. Figs:______

2. Measure the same rectangle with a ruler that can be read to the nearest millimeter. Again, record the number of significant figures and circle the estimated digit. Recalculate the area of the rectangle.

Length:______Sig.Figs:______

Width:______Sig Figs:______

Area:______Sig. Figs:______

3.  Suppose the rectangle was a solid object that was 2.00 cm in height. What would the volume of the solid rectangles be in #1 and #2 above? Calculate the volumes using all of the digits. Round off and express the volumes to the proper number of significant digits.

A. L = W= H = 2.00 cm Volume = ______cm3

B. L = W = H = 2.00 cm Volume = ______cm3

Questions

1.  Define significant figures.

2.  How does the sensitivity of the measuring device affect the number of digits that can appear in an answer to a calculation?

3.  Each of the following values was read on an instrument of measuring device. In each case the last digit was estimated. Tell what divisions would have been made on the scale or measuring device.

a.  example: 16.00 The scale read to tenths; hundredths were estimated

b.  16 g

c.  16.00 mL

d.  160 cm

e.  1600 g

f.  160.0 g