Perform the steps of the lab. Then write up the lab with a clearly marked procedure paragraph, observation paragraph, and conclusion paragraph.
In the procedure paragraph write what you did in the lab. Include the materials you used and the steps you took.
In the observation paragraph write what you saw in the lab, include your numerical data.
In the conclusion, give your conclusions and your opinions on the lab.
(You simply write up a procedure paragraph, just write what you did in a way that someone else could repeat it. Like you are explaining it to a friend. Great detail is not required.
Then in your observations you put your numerical data and any tables.
Finally, in your Conclusion write what you can conclude and your opinion on the lab.)
NOTE! I don’t know how many pages I need you to write just case I don’t know how much info you can give to get the point across. If you could please let me know how many pages you can do to get me an “A” that would be great! I do know that she only want 3 paragraphs.
EXPERIMENT 1:
Measuring Length & Mass
Objective
Chemistry is an experimental science that is dependent on gathering and reporting accurate information. This activity will teach you about measurements, their accuracy, precision, and uncertainty. You will learn techniques for measuring solids and liquids and you will learn how to evaluate the quality of the measuring device.
Introduction
Many experiments involve the measurement of mass, length, or volume. No matter how carefully you may carry out a measurement, no matter how carefully you read the measuring instruments, there will always be some uncertainty in every measured value. The uncertainty can be minimized but never completely eliminated. Even with good equipment and careful techniques, your measurement still depends on human limitations such as visual acuity when reading thermometers, analytical balances, burets, and so on. These errors are random in the sense that your reading is equally likely to be slightly more or slightly less than the true value. Instruments cannot be used to measure an infinite number of figures. The last figure recorded is a significant but doubtful one. Such instrument errors result in random errors.
If you know the actual (accepted, true) value of a measurement, you may choose to report the percent error.
Experimental value – accepted value
Percent Error = ———————————————————- X 100
Accepted value
The quality of a set of measurements is stated in terms of accuracy and precision.
Precision is a measure of how closely individual measurements agree with one another.
Accuracy refers to how closely individual measurements agree with the correct, or “true” value.
Percent error is a measure of accuracy of results, not of the precision of the measurement.
A. MEASURING LENGTH
Materials Needed
Metric ruler or meter stick
Dollar bill
A penny
Procedure
1. Observe the marked lines on a metric ruler. Identify the lines that represent centimeters and millimeters.
2. Use a ruler and measure the length of the longest edge of this lab book in centimeters. Record this length on the REPORT FORM (1). Next, measure the length of a dollar bill in centimeters. Record this length on the REPORT FORM (2). Then, measure the diameter of a penny. Record this length on the REPORT FORM (3). Finally, have two persons measure your height, A and B. Record these measurements on the REPORT FORM (4, 5).
3. Identify the estimated digit in each measurement (the doubtful digit). And identify the number of significant figures in each measurement.
B. MEASURING MASS
Materials Needed
Kitchen scale
Digital scale
100 mL beaker
Procedure
4. The first thing you must do in this experiment is zero your balances. Read the instructions on the use and care of your digital scale and your kitchen scale. Your kitchen scale should read zero when empty.
5. Weigh a clean dry 100 mL beaker on your kitchen scale. Record the weight in ounces on the REPORT FORM (6) using the proper number of significant figures in recording the estimated digit.
6. Using Dimensional Analysis (Factor-Label Method) convert the weight of the beaker into grams (1 ounce = 28.4 g). Record this value on the REPORT FORM (7).
7. With the digital scale turned on, press the “tare” to obtain a zero reading. Carefully place the 100 mL beaker on the balance pan and read its mass from the display. Record this mass on the REPORT FORM (8)
C. WEIGHING A SUBSTANCE
Materials Needed
Digital scale to 0.1 g
100 mL beaker
Table salt
Teaspoon
25 mL Graduated cylinder
Procedure
8. Determine the mass of a dry 100 mL beaker, as in B, using the digital scale. Record this value on the REPORT FORM (9).
9. Place one teaspoonful of table salt (NaCl) in the beaker. Place the beaker on the scale and record the mass on the REPORT FORM (10).
10. Calculate the mass of table salt by difference on the REPORT FORM (11).
11. Express the mass of table salt in kilograms (1 Kg = 1000 g). Record this value on the REPORT FORM (12).
12. Express the mass of table salt in milligrams (1 g = 1000 mg). Record this value on the REPORT FORM (13).
13. Express the mass of table salt in micrograms (1 ug = 10-6 g). Record this value on the REPORT FORM (14).
14. Using a graduated measuring cylinder, measure out 25 mL of water. Add the 25 mL of water to the beaker containing the table salt. Swirl to dissolve the table salt. Weigh the container and salt solution on the digital scale and record the mass of the REPORT FORM (15).
15. Calculate the mass of water added. Report this value on the REPORT FORM (16).
16. Finally, calculate the percent concentration of table salt in the salt solution. Report this value on the REPORT FORM (17).
Mass of salt
Percent salt = —————————- X 100
Mass of solution
EXPERIMENT 1: Measuring Length & Mass
REPORT FORM: Name ________________________
Date _________________________
A. Measuring Length
Item Length Estimated Digit Significant Figures
1. Edge of lab book ______ cm _____________ __________
2. Length of dollar bill ______ cm _____________ __________
3. Diameter of penny ______ cm _____________ __________
4. Your height A ______ cm _____________ __________
5. Your height B ______ cm _____________ __________
Questions and Problems
Did each person get a different value for your height? If so, why did they?
Using either value, calculate your height in inches (1 in. = 2.54 cm)
B. Measuring Mass
Weight of beaker
6. Kitchen scale ______________oz
7. Calculated weight ______________g
8. Digital scale ______________g
Questions and Problems
Compare and contrast accuracy and precision of your kitchen scale to the digital scale.
Weighing a substance
9. Mass of beaker ______________ g
10. Mass of beaker and salt ______________ g
11. Mass of table salt ______________ g
12. Mass of table salt in kilograms ______________ Kg
13. Mass of table salt in milligrams ______________ mg
14. Mass of table salt in micrograms ______________ ug
15. Mass of beaker and salt solution ______________ g
16. Mass of water added ______________ g
17. Concentration of salt solution ______________ % salt
