Welcome student:

Course Documents:




Weblog
Discussion Board
Chemistry Syllabus
 Chime Molecular Models
 Chemistry Text Resources
Graphical Analysis Tutorial
Physlets
Homework Calendar
Semester Test Reviews

District 228 Materials:



District 228
Tinley Park High School
IMC Resources
Reading Templates


Keith Kuykendall
Science Teacher
Tinley Park High School
6111 W. 175th Street,
Tinley Park, IL 60477
708-532-1900x3912 kkuykendall@bhsd228.com

Mass | Volume | Length | Finally

Density Lab:

Part 1: Mass

Gather materials:

1. density samples one metal cube, one metal cylinder

2. balance

3. ruler, graduated cylinder from your storage locker

Using the balance:

1. Make sure that when the pan is empty, and all sliders are at their respective zeroes, the balance, balances (the index marks align).

2. Never place an object to be massed directly on the balance pan (why?). Instead place a clean, dry container capable of accomodating the sample on the pan (a beaker of appropriate size or a piece of weighing paper) and determine the mass of the container. Record the container's mass, add the sample, determine and record the total mass, finally determine the sample's mass by subtraction.

3. In making each determination move the largest slider outward one notch at a time. Once placement tips the balance, move back one notch. Make sure that the largest slider is completely settled in a notch before moving the second slider.

4. Move the second slider just as the first.

5. Using the tip of a pencil, push the last slider slowly outward on the beam until the index marks align perfectly, record the value on the balance.

Reading a balance:

Examine the three images below along with their text. Notice that the last digit always "estimates" to the tenth of the finest scale division. These photos illustrate a "milligram" balance. We are using a "centigram" balance. Can you anticipate the difference?

Test your skill in massing:

1. Mass two small beakers (just big enough to contain either unknown mass).

2. Using one balance, mass each object twice (once in each beaker). Be sure you record each measurement to tne nearest .01 g.

question: by how much did the mass measurement differ as a result of using different beakers?

3. Swap balances with another group. Repeat number (2) using the same beakers and unknown masses.

question: by how much did each absolute measurement (mass of beaker, mass of beaker + unknown 1 etc.) differ from balance to balance?

question: by how much did the ultimate determination of mass (mass of unknown cube, mass of unknown cylinder) differ from balance to balance?

question: does your experience suggest that using the "differences method" has greater reliability?

 

 

 

 

 

© 2004 by Keith Kuykendall. All rights reserved.