Science Buddies: "Ask an Expert"

WHAT IS THE DIFFERENCE BETWEEN ELECTRONIC BALANCE AND AN ELECTRONIC SCALE. MY DAUGHTER'S SCHOOL HAS AN ELECTRONIC SCALE SHE CAN BORROW FOR HER PROJECT BUT NOT A BALANCE. HER PROJECT SAYS REQUIRES A BALANCE. CAN I USE THE SCALE? ANTIMICROBIAL PROJECT

Hi there,

Both a scale and a balance measure weight, and it may be that the scale available at her school will suffice. The most likely difference (if any) is the sensitivity, or the units of measure. In general, a balance is very sensitive and can detect very small differnces in weight (less than a gram). A scale usually refers to something that measures larger units, like pounds or kilograms. However, it may be that what your daughter's school calls a scale actually does measure small units of mass. When it comes to very small organisms - like microbes - you'll need a balance that measures very small units of mass.

Does that answer your question?

Heather

Yes! Thank you! That makes sense. This is my first time doing a project with the kids and I think I may have bitten off more than I can chew! I appreciate your help. I believe she will need to measure any organisms that may have grown from her samples taken each day from the solutions containing the different amounts of preservatives to check which amount works the best to preserve the product completely. whew! Hope that makes sense! Let me know what you think? If a scale may do the job? Thanks so much!
Cyndee

If I understand the project correctly, you would probably need a fairly sensitive balance in order to detect the growth of microorganisms by weight. Have you considered growing the microorganisms in petri dishes and comparing the coverage of the plates?

Here are some Science Buddies resources about growing microorganisms.
All About Agar: https://www.sciencebuddies.org/science- ... Agar.shtml
Inoculating the agar plates: https://www.sciencebuddies.org/science- ... tion.shtml
Interpreting the plates: https://www.sciencebuddies.org/science- ... ates.shtml

Please let me know if this is helpful, or if I am off base here. And let me know if you have any more questions!

Heather

Thanks for your replies! Yes- that is exactly what she is doing. She is doing the microorganism preservative project on the "Science Buddies" web site. We have made the dishes and ready to start but not sure how to measure the microorganisms... (It is to my understanding that is what the project entails). I appreciate your help. I will check out the resources you have sent! Thanks!
Cyndee

Hi Cyndee,

Typically, when you grow organisms on agar plates, you will count the number of colonies (if the number is small), or measure the percentage of the plate that is covered by growth (if the colonies are numerous and have grown together). That is sufficient to measure the amount of bacteria. If the plates are completely covered, you can also try diluting the sample before you plate it out, which will give you fewere colonies, but is still comparable if you dilute all the samples the same way. For all of these methods, you do not need to measure the weight of your samples. A good strategy is to also take pictures of the growth, for presentation purposes.

I hope that helps. Feel free to post again (in this same thread) if you have more questions.

Good luck!
Heather

AWESOME! THANKS SO MUCH FOR ALL OF YOUR HELP! YOU DONT KNOW HOW MUCH THAT HELPS ME! I THOUGHT I NEEDED THE BALANCE TO MEASURE THE COLONIES! LOL = SO THANKFUL! NOW WE CAN GET THIS DONE AND I LOVE THE PICTURE IDEA! THANKS SO SO MUCH!
CYNDEE

Glad to help. Please let me know how it goes!

Best wishes,
Heather

Heather - I sure will. We will start tomorrow and thanks to you I am sure it will be great! Thanks again!
Cyndee

Heather? Do you have an Email address?
Cyndee

Hi Cyndee,

Yes, I have an e-mail address, but we are not allowed to post personal information (including e-mail addresses) on this forum. Since others can benefit from your questions and the results you post, it's best to keep our communication on the forum.

Heather

Okee Dokee - well dern! - Just wanted to say thanks for the help and send u a pict... not sure how to do that on here - haha .... But all went great! Just wanted to say thanks again and let ya know it went well. Thanks!
Cyndee