Have you ever thought about how accurate your volumetric measuring tools are? How do you know your measuring cup is calibrated? Is it good science to use your kitchen tools for science? Today’s discussion is Comparing the Accuracy of Liquid Measuring Tools.
Are All Volumetric Measuring Tools the Same?
The gold standard in measuring volume is the Volumetric Flask. It’s a laboratory flask which is calibrated precisely to a certain volume at a particular temperature. They come in various sizes from 1-10,000 mL of liquid. But, they are also expensive and they are typically not found in classroom labs or homes because neither work with extremely precise volumes of liquid.
So, what do we use instead? The rule of thumb is to use the graduated cylinder. With all the markings on the cylinder, it is considered more accurate than other volume measuring tools. But, is there a big difference? We decided to test them to see.
Tools for Measuring Volume
What are some tools available for measuring volume?
- Beakers- Are containers primarily used for mixing and heating. There are markings on them for measuring, but they are meant to be approximate.
- Measuring Cups- The liquid measuring kitchen variety. We use Pyrex brand.
- Erlenmeyer Flasks- These are wide bottomed but not circular with a neck that can use a stopper (with or without holes). It makes a good reaction vessel and allows a larger area for smaller volumes.
- Florence Flask- This is a round bottomed flask used for boiling solutions.
- Field Collecting Tubes- These are screw top collecting tubes which come in 15 mL or 50 mL and they are terrific for collecting aquatic specimens in the field. We use them during our entomology excursions.
- Pipettes- Used for moving small volumes of water or removing liquid in small increments. I like the disposable kind because the cleaning is much easier!
- Graduated Cylinder- Are used for measuring volumetric quantities. They range in size from 10- 1000 mL. If you are going to choose only one, the 100 mL size is a good one.
So, if you want to use something other than what’s found in your kitchen, where do you get them? We use Home Science Tools. We order some specialty items, like collecting tubes, from BioQuip. Just for fun, we also visited our local university’s chemistry supply room. Armed with gift money, our then 8 year old, took a trip with Dad to pick out his own glassware.
Testing the Accuracy of Volume Measuring Tools
Since we used the graduated cylinder as our gold standard, we chose to determine the final volume in a graduated cylinder. Our procedure:
- Choose a beaker, flask, or collecting tube and fill it with water to the highest marked volume in mL.
- Record that volume in your data chart which will be labeled with the containers you are using.
- Pour the contents of the first container into the appropriately (closest) sized graduated cylinder available.
- Measure the volume of water in the graduated cylinder
- Record the volume.
- Repeat using various sized measurement tools.
How to Record Data When Doing a Science Exploration
The data chart for recording volume was designed by each student separately based on what we needed to write down. Here are a few things to remember about data charts and recording data.
- Have each student design her own based on ability- parents can step in when columns are missing.
- Give hints or general categories students need to remember when constructing their own chart. It’s ok if the charts turn out differently from others as long as they record everything.
- Creating their own data chart is a great way to learn the skill of organizing information. I think we underestimate the importance of our homeschooled students being able to organize information on their own- without the help of a printable!
- Remember printables are fun, but they aren’t necessary and sometimes they slow you down- like when you are spending all your time looking for ones you’ve already printed or when you can’t find just the perfect one.
- Scientists in the field must create their own data charts since they often design their own experiments. Step boldly!
Our Findings- How Accurate are the Volumetric Tools?
What were the results?
- All volumetric containers are not the same!
- The graduated cylinder has more markings and measures more accurately – it was certainly easier to determine an accurate volume with more gradations.
- The readings on the graduated cylinder were higher than the same volume measurement in the other tools.
- The larger the container, the larger the discrepancy. The largest beaker was off my 20 mL or more!
What does it all mean? Well, it means if you want accurate volume without using a volumetric flask, use the graduated cylinder for the best results. Always use the container that will reasonably hold your liquids. If you use the extreme opposite, your readings will be less accurate.
Does My Homeschool Need Volumetric Measuring Tools?
Some of you might be asking whether or not it’s a good idea to invest in some volumetric containers for your homeschool. Is it a good idea? Here are a few things to think on:
- Using containers meant for science frees up your kitchen tools- I prefer to use science tools for science and kitchen tools for the kitchen. That might be the science teacher talking, but it’s more than that!
- Some chemicals don’t belong in vessels we eat from- Perhaps your wet labs aren’t dangerous, but some of them might be.
- Using science tools reinforces safety measures- We don’t eat in the lab! Nor should we really eat from vessels used in the lab.
- Ensures your students know how to measure volume accurately using appropriate tools
- Your students will be versed in labware and how to use it
- It helps our science to be more accurate- rather than guessing at volume when your liquid falls somewhere between 50 mL marks!
It’s easy to start out with a few beakers and graduated cylinders. We have a mixture of plastic and glass, but plastic lets me relax a little more. I would recommend a 100 mL graduated cylinder, 250 & 500 mL beakers at a minimum to start. If you work in small volumes, a 10 mL graduated cylinder is a good size.
Even the simplest of labs can introduce a great deal of concepts and provide plenty of practice at homeschool science. It’s important to use scientific volumetric tools as much as possible. Your measurements will be more accurate!by