Colegio San Agustin - Makati
CHEMISTRY LABORATORY ACTIVITY SHEET
SY: 2012 – 2013 / CSA SCIENCE PROMOTES
THE CULTURE OF EXCELLENCE
ACTIVITY # / 2 / Measurements in Chemistry
REMARKS
PURPOSE
To solve problems by making accurate measurements and allying mathematics.
To determine the mass of several chemical compound samples and use the data to count atoms.
Organize the lab report in such a way that the different parts of this activity will presented properly.
MATERIALS
Part 1: Now What do I do?
Pencil
Paper
Meter stick
Balances (triple beam, platform, top-loading)
Pair of dice
Aluminum can
Calculator
Small-scale pipet
Water
Plastic cup / Part 2: WEIGHING AS A MEANS OF COUNTING
Pencil
Paper
Balance
Plastic spoon
Balance
Ruler
Chemicals
H2O
NaCl
CaCO3
SAFETY
Wear your goggles and laboratory gown at all times during the investigation.
PROCEDURE
Part 1
  1. Determine the mass, in grams, of one drop of water using a top-loading electronic balance. To do this, measure the mass of any empty cup. Add 50 drops of water from a dropper to the cup and measure its mass again. Subtract the mass of the empty cup from the mass of the cup with water in it. To determine the average mass in grams of a single drop, divide the mass of the water by the number of drops (50). Repeat three (3) times this experiment until your results are consistent.
  1. Repeat Step 1 using the triple beam balance and the platform balance.
  1. The following small-scale activities allow you to develop your own procedures and analyze the results. Include the procedures of the “Design it”in your lab report and the necessary analysis and answers to questions.
  2. Design it: Design an experiment to determine if the size of drops varies with the angle at which they are delivered from the dropper. Try vertical (90o), horizontal (0o), and halfway between (45o). Repeat until your results are consistent.
Analyze it:What is the best angle to hold a dropper for ease of use and consistency of measurement? Explain. Why is it important to expel the air bubbles before you begin the experiment?
  1. Design it: Make the necessary measurements to determine the volume of aluminum used to make an aluminum soda can. Hint: Look at the density of aluminum (2.6989 g/cm3).
  1. Design it: Measure a room and calculate the volume of air it contains. Estimate the percent error associated with not taking into account the furniture and people in the room.
  1. Design it: Make the necessary calculations to determine the volume of a pair of dice. First ignore the volume of the dots on each face, and then account for the volume of the dots. What is your error and percent error when you ignore the holes?
  1. Design it: Design an experiment to determine the volume of your body. Write down what measurements you would need to make and what calculations you would do. What additional information might be helpful?
Part 2
  1. Measure the mass of one level teaspoon of (NaCl), (H2O), and (CaCO3). Make a table similar to Figure A.to record your measured and calculated data.
  2. Design an experiment that will determine the number of atoms of calcium, carbon, and oxygen it takes to write your name on the chalkboard with a piece of chalk. Assume chalk is 100% calcium carbonate.

OBSERVATION
Data Table
H2O (l) / NaCl (s) / CaCO3(I)
Mass (grams)
Molar Mass (g/mol)
Moles of each compound
Moles of each element
Atoms of each element
Figure A
QUESTIONS
Analysis
Part 1: Using your experiment data, record the answers to the following questions.
  1. What is the average mass of a single drop of water in milligrams? (1 g = 1000 mg)
  2. The density of water is 1.00 g/cm3. Calculate the volume of a single drop in cm3 and mL. (1 mL = 1 cm3) What is the volume of a drop in microliters (um)? (1um = 1mL)
  3. What is the density of water in units of mg/cm3 and mg/mL? (1 g = 1000 mg)
Part 2: Using your data, record the answers to the following questions in or below your data table.
  1. Calculate the moles of NaCl contained in one level teaspoon and record the result in your table.
  2. Repeat Step 1 for the other compounds in Figure A. Use the periodic table if necessary to calculate the molar mass of water and calculate the molar mass of water and calcium carbonate.
  3. Calculate the moles of each element present in the teaspoon-sized sample of H2O. Repeat for all the other compounds in your table.
  4. Calculate the number of atoms of each element present in the teaspoon-sized sample of H2O. Repeat for all the other compounds in your table.
  5. Which of the three teaspoon-sized samples contains the greatest number of moles?
  6. Which of the three compounds contains the most atoms.

REFERENCE
Wilbraham, et al. Chemistry 5th Ed. pp.96 and 187