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20200131193831chem Measurement

Content type

User Generated

Subject

Chemistry

School

CUNY Hostos Community College

Course

General chemistry 105

Type

Homework

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fgneqbanyq96

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Measurements in the Laboratory

I. Introduction:

Measurement plays a vital role in studying chemistry. It provides us quantitative information about

a certain object of interest. It is important for you to understand the concept of accuracy and

precision and introduce you to some measuring devices that can be found in the laboratory. These

measuring devices can be the cause of error making your data inaccurate and sometimes incorrect.

At the end this laboratory, students will be able to:

a) Use standard laboratory measuring devices to measure length and mass.

b) Apply the concept of significant figures for data consistency.

c) Use the measurements gathered to determine area and mass.

II. Materials:

Ruler

Shape sheet

Calculator

III. Procedure:

Part A. Measuring the dimensions of regular geometric shapes.

1. Borrow a ruler and “shape sheet” from the front bench. Record ID code on your report form.

Measure the dimensions of the two geometric shapes: length and width of the rectangle, and

the diameter of the circle. Record these values.

2. Once done, return the ruler and the sheet to the front bench.

3. Use the formula for area of each shape.

Area of rectangle: A = lw

Area of circle = A = πr

Part B. Measuring the Mass of solids.

Comparing the precision of two types of balances.

1. Obtain a 250-mL Erlenmeyer flask from your locker. Use the triple-beam balance to determine

the mass of this flask.

2. Use the electronic balance in the weigh room to determine the mass of the Erlenmeyer flask.

Record your measured reading on your lab report.

Weighing by difference

3. Obtain a 100 mL beaker from your locker. Use the electronic balance in the weigh room to

determine the mass of the beaker.

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4. Add two spoonfuls of sugar to this beaker using your scoopula. Do not do this over the balance!

Determine the new combined mass of both beaker and the sugar. Be sure to use the same

electronic balance as before. When finished, dispose the used sugar in the sink.

5. Use these two measurements to calculate the mass of sugar by difference.

IV. Results:

Part A. Measuring the dimensions of Regular Geometric Shapes

Experimental Data:

Shape Sheet ID Code: Circle 29

Shape

Dimensions

Precision

Measurement

# Significant Figures

Rectangle

Length

5.7 cm

2 sig. fig.

Width

3.0 cm

2 sig. fig.

Circle

Diameter

7.5 cm

2 sig. fig.

Data Analysis

1) Perform the conversions indicated. Show your work and report your answers in scientific

notation.

a. Convert the measured rectangle length to hm.

Length measured: 5.7 cm

Conversion of cm to hm: 1 cm = 0.0001 hm = 1 x 10

-4

Converting:

  









  





b. Convert the measured circle diameter to nm

Diameter measured: 7.5 cm

Conversion of cm to nm: 1 cm = 10000000 nm = 1 x 10

Converting:

  









  





2) Calculate the areas of your rectangle and circle in cm

. Show your work and report your answers

to the correct number of significant figures.

a. Area of rectangle

Length = 5.7 cm

Width= 3.0 cm

Area = Length x Width = 5.7 x 3.0 = 17.1 cm

= 17 cm

The answer should be rounded to the lease significant figure since this is multiplication and

division. Therefore, it should be 2 significant figures.

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Measurements in the Laboratory I. Introduction: Measurement plays a vital role in studying chemistry. It provides us quantitative information about a certain object of interest. It is important for you to understand the concept of accuracy and precision and introduce you to some measuring devices that can be found in the laboratory. These measuring devices can be the cause of error making your data inaccurate and sometimes incorrect. At the end this laboratory, students will be able to: a) Use standard laboratory measuring devices to measure length and mass. b) Apply the concept of significant figures for data consistency. c) Use the measurements gathered to determine area and mass. II. Materials: Ruler Shape sheet Calculator III. Procedure: Part A. Measuring the dimensions of regular geometric shapes. 1. Borrow a ruler and “shape sheet” from the front bench. Record ID code on your report form. Measure the dimensions of the two geometric shapes: length and width of the rectangle, and the diameter of the circle. Record these values. 2. Once done, return the ruler and the sheet to the front bench. 3. Use the formula for area of each shape. Area of rectangle: A = lw Area of cir ...
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