CHARLOTTE, N.C. â We're all about making this Science Sunday fun and Halloween-themed, so I give you... making witches brew!
What you'll need:
- Jar or cup
- Cooking oil
- Water
- Food coloring
- Alka seltzer tablets
We did something similar for Science Sunday last winter when we made a snowstorm. But today we're focusing on differences in density and how that applies to the weather.
What you'll do:
- Fill your jar about three-quarters of the way with cooking oil. For this experiment, we used vegetable oil.
- Fill the rest of the jar with water. *Note: to avoid spillage in the studio or our clothes, I chose jars with lids.
- Add a few drops of food coloring in any color of your choice. Notice that the oil and water never mix, even when you add the food coloring, which is another liquid.
- Add Alka Seltzer tablets and see what happens!
What's the science?
Liquids all have differences in density and viscosity, which refers to the thickness and resistance to flow. Density refers to how tightly packed atoms and molecules are within a substance. The more tightly packed, the higher the density.
When liquids have different densities and you put them together, they will not mix. That's why the water stays on the bottom of the jar while the oil stays on top. Even when you add the food coloring, the substances stay separate while the color of the water changes and it mixes with the color.
This is similar to how weather happens.
Different air masses (cold, and warm) are always present across the country, with cold air masses being denser than warm air masses. Warmer air masses have less density because warm molecules move and bounce around faster than cold, allowing them to be less tightly packed.
This is important to understand when things like cold fronts move through the Carolinas. The cold air replaces the warm air mass by moving it essentially up and away. Additionally, replacing air masses allows for big swings in temperature, humidity, and pressure, which can impact how people feel when they're outside, especially during fall and winter.
The second thing we explore here is the chemical reaction between Alka Seltzer and water. This creates carbon dioxide bubbles, which causes the mixture to rise. Colored bubbles of carbon dioxide attach themselves to water, rising to the top of the glass before settling again.
Contact Brittany Van Voorhees at bvanvoorhe@wcnc.com and follow her on Facebook, X and Instagram.