Category Archives: Messy

Expand on the Activity:

• What color changes did you see? Did you notice any patterns?

• If you use vinegar or lemon juice, what do you think will happen to the color of the DIY pH indicator if you add baking soda or an antacid tablet

• For another hands-on chemistry experiment, try making your own STEM slime activity! 

The Science: pH and pH indicators

• pH is a measurement of how acidic or basic something is. It is measured on a scale of 0-14.
• A substance with a pH of 7 (like distilled water) is neutral. A substance with a pH of less than 7 is an acid. The closer the number gets to zero, the stronger the acid is. A substance with a pH of more than 7 is a base. The closer the number is to 14, the stronger the base is.
• Strong acids and bases can be very dangerous, while weaker acids and bases (those with a pH close to 7) are safer to use.
• We find acids in many of the foods we eat, as well as in our stomachs. Acids found in foods give them a sour taste.
• Bases are commonly found in cleaning products and antacid medications. Bases feel slippery and are rare in food because they taste bitter. For reference, think about the taste of soap!
• pH indicators are compounds that change color in the presence of an acid or a base.
• Different pH indicators have different ranges. Some may only be able to show whether something is acidic or basic, while others may have a wide range of colors that can show different strengths of acids and bases. Some may be better for showing the pH of acids, while others may be better at showing the pH of bases. In a lab, the best indicator to use depends on the pH range you want to see.

Learn More: Chemistry

• There are several different definitions of acids and bases in chemistry.
• A simple chemical definition of an acid is a substance that releases hydrogen ions (H+) when dissolved in water. A simple chemical definition of a base is a substance that makes hydroxide ions (OH-) when dissolved in water or a substance that takes hydrogen ions from an acid.
• Ions are positively (+) or negatively (-) charged particles of an element.
• Many red, purple, and blue plants contain chemicals called anthocyanins, which are weak acids that dissolve in water and change color in response to changes in pH. Because of this, plants with anthocyanins like red cabbage and blueberries can easily be made into pH indicators.

Did you make and test your own indicator? We’d love to see how it turned out! Snap a photo of you making or experimenting with your indicator and submit it to our Science Showcase here or use #OSCatHome on social media!

Experiments:

Once you’ve made your oobleck, it’s time to do some experiments! Before you perform you start this STEM slime activity, make some predictions. Is the oobleck a solid, a liquid, or a gas? What will happen if you poke it? What will happen if you let it sit in your hand?

TRY:

• Poking the oobleck with your craft stick. How does it feel?
• Gently stepping your craft stick on top of the oobleck. What happens?
• Holding the oobleck in your hand. What happens when you squeeze it? What happens when you let go?

Expand on the Activity:

• What happens if you pour oobleck through a container with holes in it, like a colander or a strainer?

• What happens if you put plastic or LEGO figures in the oobleck? What stories can you tell? Use your imagination!

• Use highlighter water to make oobleck that glows under a blacklight!

• Make more! This recipe gives you a small amount of oobleck, but as long as you add twice as much cornstarch as water, you’ll have oobleck!

The Science Behind this STEM Slime Activity: Why Does Oobleck Act Like This?

• Oobleck is made up of molecules called polymers, which are arranged in long chains. A great example of a polymer is a rubber band. The molecules can be stretched out or bundled up and stuck together like wet spaghetti.
• When you put pressure on the oobleck, the molecule chains bundle up and stick together, making the oobleck act like a solid.
• When there is no force on the oobleck, the polymers stretch out, and the oobleck acts like a liquid.
• Since oobleck can be a solid or a liquid depending on whether you apply force to it, it is called a non-Newtonian fluid.

Learn More: Physics

• In a solid, the molecules are tightly packed and vibrate in place. In a liquid, the molecules slip past each other, allowing liquids to flow. But have you ever noticed some liquids flow faster than others? Think about water versus honey. What makes them flow differently?
• You can find out by rubbing your hands together quickly. What do you feel? That heat is from friction, or force that holds back the movement of a sliding object. As the molecules in a liquid slide past each other, they generate friction, too. The more friction they generate, the slower they move. Why is that? The force of the friction is holding back their movement, effectively slowing them down.
• The friction between molecules in a liquid is called viscosity. The more viscous a liquid, the more energy it takes for it to flow. High visocity liquids, like honey or corn syrup, also tend to be thicker.
• So what about oobleck? Oobleck is called a non-Newtonian fluid because it breaks the rules of Newtonian viscosity. On Earth, they’ll always be subject to the laws of gravity and the laws of motion Newton described. But the viscosity of oobleck, or the interactions and friction between the molecules, changes based on force you apply to applied to it.

Did you make your own oobleck and perform any experiments with it? We’d love to see how it turned out! Snap a photo of you making, testing, or playing with your oobleck and submit it to our Science Showcase here or tag Orlando Science Center and use #OSCatHome on social media! You might be featured on our channels.