How do you make cheese?

Last week in Sisters4Science at Reavis, we learned about food science with our guest scientist Daina!

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First, the Sisters shared what they knew about cow milk–Aaliyah remembered that it had proteins and vitamins in it, and we also discovered that milk has lactose, which makes milk sweet.
Each Sister tasted two different types of Greek yogurt, a piece of mozzarella cheese, and a piece of parmesan from Wisconsin. We found that one type of yogurt was more sour than the other; the mozzarella didn’t have a very strong taste; but the parmesan was harder than the rest, and sort of tangy or nutty. Even though all of these foods were made from cow milk, they were all made in different ways, which is why they look and taste so different!
With some styrofoam models, we discovered that milk molecules have structures called “casein micelles,” which keep the molecules far apart and the milk liquid. By using acid or an enzyme called rennet, we can break these up and allow the molecules to come closer together to make something solid (like cheese!).
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So, we tried it out! Each Sister added acidic lemon juice to milk, and then filtered it to get the whey out. We also tried adding rennet to milk, and it become much more solid. To test the acidity of each mixture, we used red cabbage, which changes color based on pH. We saw that the whey we made was more acidic than the milk, which was more acidic than water. We learned a lot, and had the opportunity to try some new foods too! Great job, Sisters!
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Animals!

Last week in Sisters4Science at Reavis, we welcomed Ms. Brianna from the Anti-Cruelty Society and learned all about careers with animals!

First, Ms. Brianna asked us all if we had any pets; Aaliyah has a dog, and Mahogany and Kemonte both have cats. Ms. Brianna works in the Anti-Cruelty Society, which is an animal shelter that takes care of pets that don’t have homes. We learned about cool jobs you can get in an animal shelter, like a veterinarian, a vet tech, and an animal trainer. The Sisters got to try using a clicker, which animal trainers use–it makes a sound that signals to animals that they did something good, and then the animal is more likely to repeat that action (like sitting, for example). Kemonte wants to get a clicker so that she can train her cat to do tricks!
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The Sisters were very curious about animals, so they asked Ms. Brianna A LOT of really great questions, like Where do dogs and cats come from? We learned that dogs evolved from wolves over a very long time, because humans started using wolves to help take care of livestock or to hunt. Some types of dogs come from different places–chihuahuas come from Mexico! Mahogany was very interested to hear that cats came from ancient Egypt (where people used to worship them!)
The Sisters also asked about various biological things related to animals. Aaliyah knew about procedures called neutering (for males) and spaying (for females), which prevents pets from reproducing. This is very important, as Mahogany said, because cats can have up to 12 kittens at a time! We also learned that when cats like you, they rub against your leg because that spreads their pheromones on you, which marks you as “theirs.”
It was a fun and engaging session, made much better by the great questions and excitement brought by the Sisters. Awesome job, ladies!

Strawberry DNA

Last week in Sisters4Science at Reavis, we welcomed Ms. Joyce, and she taught us how to extract DNA from strawberries!

First, the Sisters shared with everyone what they already knew about DNA–Aaliyah remembered that it was in human cells, and Kemonte recognized DNA because it was used on the Jerry Springer Show to see if two people were related. Ms. Joyce and the Sisters agreed that DNA can be found in any living thing: humans, animals, plants, and even bacteria! Then we found out an easy way to see DNA (without a microscope).
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Each of the girls took a strawberry in a ziploc bag and smashed it all up to break the cells. Then, we added “DNA extraction buffer” (soap, salt, and water) to the mashed strawberry. We poured our strawberry/buffer mixture through a coffee filter so that strawberry juice with DNA in it would drip down into a plastic cup, separate from proteins and cells and other strawberry bits. After a little bit, each Sister added the strawberry juice to a tube of alcohol, and when we swirled it around, we could see DNA in the tube! The Sisters observed that the DNA was whitish and gooey; Mahogany said it looked like saliva.
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We closed the session by talking about contributions that women have made in DNA research: Rosalind Franklin was a scientist who was very important in discovering the structure of DNA, the double helix. Because the Sisters were able to take the small-scale model of strawberry DNA extraction and apply it to a larger concept or idea (like extracting DNA from human cells to test them and see if people are related), they earned the Discover Building Models badge. That’s the last badge; good job, Sisters!
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Mae Jemison and the Solar System

Last week in Sisters4Science at Reavis, we learned about Dr. Mae Jemison.

First, we talked about what role models are (“Someone you look up to,” according to Kemonte). The girls shared their role models with everyone; both Alita and Tayla look up to their older sisters as role models!
Then, we learned about the life of Dr. Mae Jemison. Mae Jemison was the first African American woman to go into space. Each of the girls got a book–The 100 Year Starship–and we read about Jemison’s plans to create a starship that can travel outside of our solar system!
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We discussed how Jemison may be considered a role model for us, and looked to some quotes of hers for inspiration. Mahogany explained that you shouldn’t let other people bring you down after reading this quote from Jemison: “Never be limited by other people’s limited imaginations…You can hear other people’s wisdom, but you’ve got to re-evaluate the world for yourself.” When we talked about the meaning of this quote by Mae Jemison–“The best way to make dreams come true is to wake up”–Tayla explained that you have to work to make your dreams come true, and you can’t just expect them to happen on their own. Then, Tayla brought up another quote she had heard before–“Hard work beats talent when talent fails to work hard”–because she thought they both had the same message. This was a very impressive analysis of Mae Jemison’s ideas!
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The girls wanted to talk a little more about the solar system, so they each went to the board and drew out a model of the solar system, wrote the names of the planets, and discussed how big the universe might actually be and whether aliens might exist. Since different planets take a different amount of time to orbit the sun, a “year” is a different number of days, so we all calculated our “age” on other planets. On Mercury, our Sisters are 54 years old!
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Proteins and Pineapples

This week in Sisters4Science at Reavis, we learned about proteins and proteases with our guest scientist, Erin!

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Erin brought water, jello mix, canned pineapples, and fresh pineapples. Each girl got three test tubes–one to put fresh pineapples in, one to put canned pineapples in, and one to leave empty. Then, we each used a pipette (something that measures liquid) to transfer the water and jello mix to our test tubes.
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We learned that jello is made of gelatin, which is a protein. Some types of proteins, especially the ones in pineapples, are called proteases–which are proteins that cut up other proteins. With this information, we made a hypothesis: Kemonte and Jasaande thought that the canned pineapple had more protease, and Alita and Aaliyah thought the fresh pineapple had more protease. We agreed that if the pineapple has protease, then the proteins in the jello will be cut up, so it won’t set properly and it’ll still be a liquid instead of a solid.
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Erin taught us all about animal cells, and where proteins fit into the structure of life (from community to organism to tissue to cells to organelles to proteins!). Aaliyah asked some really great questions about the structure of a cell, and Jasaande shared with us what she knew about the difference between plant and animal cells. Then, Alita informed us all about her knowledge of sickle cell anemia and how it affects red blood cells, and Erin explained to us how it works, while Kemonte kept the timer to make sure we would take out our experiment and see the results at the right time.
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In the end, we saw that the test tubes with no pineapple and with canned pineapple had solid jello, but the one with fresh pineapple was still a liquid! Erin explained to us that, when pineapples are canned, they get heated to kill bacteria, and the heat ruins the proteases so they won’t be able to work. That’s why canned pineapple reacted like no pineapple–but fresh pineapple still had proteases, so the gelatin was all cut up and couldn’t turn into a solid!
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Because of their great contributions in the session, asking relevant questions, and sharing their information, all of the girls earned their Communication Badges. Great job, Sisters!

Slime at Reavis

Last week in Reavis, we made SLIME!

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After having a ton of fun last week with oobleck, the Sisters at Reavis requested that we make slime this session.
How do you make slime? First, you add Borax powder to water, then add glue to water (with food dye), and then you mix them together! The result: sticky, gooey, BLUE slime!
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After we made the slime and played with it for a while, the Sisters took charge and were very creative about the types of experiments they wanted to do with it. Kemonte put her slime over the heater and Alita put her slime near the window to see how heat and cold would affect the solidity of the slime. Jasaande added some more Borax to her slime (which made it less gooey and more solid), and Aaliyah added some more food dye to make it a deep, darker blue.
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Then, the Sisters wanted to see if we could combine our knowledge from last week with what we learned this week. We took out the extra cornstarch that we used to make the oobleck, and some of the girls tried to add cornstarch to their slime to make a slime/oobleck combination. The slime turned white from the powder, and according to Aaliyah, it also got a little bit harder!
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I’m so proud of my Sisters for thinking of creative experiments like these, and for using the scientific method (without even realizing it!) to explore their creations! Great job, ladies!

OOBLECK

This week, the Sisters at Reavis made oobleck!

First, the girls talked about whether they thought there were essentially two different kinds of people in the world (like cat people vs. dog people). The consensus they came up with was: No! People are essentially the same, and there’s no need to divide them up.
Great! Now, on to our lesson: As it turns out, there are two different kinds of fluids in the world. There are Newtonian fluids, which have a single density and can’t be compressed. Most fluids that we think of, like water, are Newtonian–if you put your finger in a cup of water to push it down, the water doesn’t push back; it just moves out of the way. On the other hand, oobleck is a non-Newtonian fluid–its density can change, and it can be compressed like a solid. Let’s see it in action!
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Oobleck is made by mixing cornstarch and water (adding just a few drops of food dye for color). We mixed it up in a large bowl and tried to get the proportions just right. The Sisters got messy–cornstarch and water everywhere! But finally, we got it!
Experiment time: What happens when you hold oobleck in your hands? Now, what happens if you roll it up, or if you push on it?
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The answer is very surprising! When you hold oobleck without putting force on it, it flows through your hands like a liquid; but when you push on it or roll it between your hands, it hardens and acts like a solid!
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Each Sister scooped some oobleck into a ziploc bag and began experimenting in various ways: Alita added some more cornstarch to see what would happen, and Aaliyah started throwing it against the ceiling to see if it would harden on impact. Then, they each took their oobleck home to do further experiments–Kemonte wanted to put the bag in her freezer to see if the water and cornstarch would separate and freeze. We’ll catch up with the results next week in Sisters4Science at Reavis!
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