Is My Procedure for Calculating Water Density in a Chemistry Lab Correct?

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Discussion Overview

The discussion revolves around the procedure for calculating the density of water in a chemistry lab. Participants explore the methodology for measuring mass and volume, the concept of density, and the implications of using graduated glassware. The conversation includes both procedural verification and conceptual understanding.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant seeks confirmation on whether their procedure for calculating the mass of water across three trials is correct and expresses uncertainty about verifying the proportionality of mass to volume.
  • Another participant explains that density is a constant property of a substance at a given temperature and pressure, asserting that for water at 25°C and 1 atm, the density is approximately 1.0 g/mL.
  • A method for calculating density is proposed, involving measuring the mass of water in a graduated cylinder at different volumes and comparing the results to check for consistency.
  • A participant confirms their understanding of the procedure after consulting with their teacher, indicating that they feel validated in their approach.
  • Questions arise regarding the definition of "graduated" glassware, with participants discussing the precision of measuring marks on such equipment.
  • Another participant questions the rationale behind dividing by 10 mL in the density calculation and mentions taking temperature in Fahrenheit, suggesting a potential misunderstanding of the procedure.

Areas of Agreement / Disagreement

Participants generally agree on the concept of density and the basic procedure for measuring it, but there are uncertainties regarding specific procedural details and definitions, indicating that the discussion remains unresolved in some aspects.

Contextual Notes

Some participants express confusion about the relationship between mass and volume and the use of graduated glassware, highlighting potential gaps in understanding the experimental setup and calculations.

Who May Find This Useful

Students and educators in chemistry, particularly those interested in laboratory procedures for measuring physical properties of substances.

lolzwhut?
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I'm curious if I'm doing this chemistry lab correctly or not. If you open the link below, you can see the lab. Basically, my job right now is to write a well formulated procedure on how to perform this lab.

So, for this lab, am I supposed to be calculating the mass of the substance (h2o in this case) in the provided methods for 3 trials? What I don't quite get is how to verify that the mass is directional proportional to its volume. I feel very unsure about my procedures I wrote. So if anyone can, would they mind checking the lab and steer me in the right direction or atleast verify if what I'm doing is right?

Thanks in advance.

https://viewer.zoho.com/docs/uaBiK"
 
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This is just a study of density, which is a property of a substance. The density is how much mass for a given volume, thus having units of grams per milliliter (g/mL = g/cm^3). At the same temperature and pressure this property is always constant provided the substance is chemically the same every time (i.e. no other chemicals were added during trials 2 and 3).

For water at 1 atm and 25 C the density is approximately 1.0 g/mL.

Verifying that the mass is always proportional to the volume is easy. You are just measuring the density at different volumes and if they are the same then you've succeeded.

For example, first get the mass of a graduated cylinder and then pour 10 mL water into it and take the mass again. Now you have [(Mass water & cylinder) - (Mass Cylinder)]/10 mL = Density of water g/mL.
Next repeat this using 7 mL of water and then 9 mL. You will get the approximately the same number!

Maybe you will get
trial 1 = 0.995 g/mL
trial 2 = 0.990 g/mL
trial 3 = 0.998 g/mL
Which is correct! You should be somewhere in this range!
 
Thanks, I was right :) I even asked the teacher, he confirmed it. Also, there's this odd question...

"What does it mean when you a piece of glassware that is "graduated" or has "graduations" on it?" Couldn't we describe graduations as precise measuring marks?
 
lolzwhut? said:
"What does it mean when you a piece of glassware that is "graduated" or has "graduations" on it?" Couldn't we describe graduations as precise measuring marks?

We can, just note that you can have a single volume or multiple volumes calibrated glass.

Compare http://www.titrations.info/pipette-burette for more details about calibrated glass.
 
mrmiller1 said:
Now you have [(Mass water & cylinder) - (Mass Cylinder)]/10 mL = Density of water g/mL.

Just curious, but why are we dividing by 10? FYI, I'm taking the temperature in Fahrenheit.
 
Last edited:

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