These are demonstrations that were curated by the Chemistry Graduate Student Association for National Chemistry Week.
Green Plants, Red Glow Photosynthesis is a chemical process through which plants make their food. They use a pigment in the leaves called chlorophyll to trap sunlight and together with carbon dioxide make their food. Chlorophyll is known to fluoresce when exposed to light. In the green plant-red glow experiment, chlorophyll is extracted from fresh spinach and the red fluorescence of the chlorophyll solution is observed. This activity introduces students to the concepts of chlorophyll and fluorescence as related to photosynthesis.
You’re Glowing! You just can’t see it. Our eyes are designed to detect visible light. Anything that radiates heat also radiates infrared light. (The reason for this is based on quantum chemistry.) So we’re glowing in a color we can’t see all the time, as are all the things around us! But, do you know what can see Infrared Radiation (IR)? A thermal camera! How does it work? Use the thermal camera to explore your surroundings. Thermal cameras are used every day to see things we can’t see with our eyes. Firefighters can find victims through smoke, animal lovers can see critters in the dark, electricians can find bad wiring through walls, all using the power of IR detection!
Tie-Dye Bandanas Take home your very own custom-dyed bandana! When dye touches cotton or other fabrics, a chemical reaction occurs, attaching the color to the fibers. This bond is very strong -so strong in fact, that they can permanently change the fabric’s color. Tie-dye has been used for years to create cool patterns. If you want to make specific designs, you can use rubber bands to protect the fabrics and control what areas the dyes will bind to.
Chromatography Butterflies Let’s make some beautiful butterflies! Chromatography is the process of separating a mixture of components into their parts. This is best illustrated by markers, which use a combination of many pigments to create smooth colors. Dipping a filter marked with the ink in water will spread the colors into wondrous patterns. Chromatography is used in many labs to find out what mystery substances are. Use this technique to make some unique patterns in your butterfly wings!
Slime Time Glue is made up of long flexible molecules (that we can’t see) called polymers. These polymer molecules slide past each other when glue is in its liquid state. When borax is dissolved in water, an ion called the borate ion is formed. When the borax + water solution is added to the glue + water solution, these borate ions help link the long polymer molecules to each other so they cannot move and flow as easily as they do in the liquid state. When enough polymer molecules get linked together in the right way, the glue solution changes from being very liquidy to a rubbery kind of stuff that we call slime!
Sun Prints Light plays an important part in our ability to see the world around us but can also start chemical reactions! Before digital cameras, analog cameras used light sensitive compounds inside of film to create “negatives,” processed in dark rooms to avoid more exposure. Some of the first photographs created were formed using a “cyanotype,” also known as a blueprint. UV light is a part of light from the sun with an extra amount of energy. When the chemical inside of the paper touches UV light, it breaks down and the resulting chemical turns dark blue. With just a rinse of water, the image is created! What can you create using stencils or leaves before the paper turns completely blue?
Lava Lamps Oil and water have different densities. Water is denser, so it sinks below the oil. Oils’ long chain molecules don’t like to mix with water’s tiny, polar molecules. When Alka Seltzer tablets dissolve in water, it reacts to make bubbles of carbon dioxide gas. The gas bubbles rise up because it is the lightest of all the parts. Along the way, it captures some of the colored water to bring to the surface of the oil. Without the light air, the water falls again. When all the gas has escaped, the water and oil separate into two layers again.
Magic Balloons Have you ever seen something fizz up when it touches something else? This is a type of reaction where two things come together, react and produce a gas. Vinegar is a dilute solution of acetic acid and baking soda is sodium bicarbonate, a base. Acids and bases commonly react together, and when these two mix, they form carbon dioxide gas. When you keep the gas from escaping, pressure builds up just like when you blow into the balloon, inflating it. This reaction is also an endothermic reaction, or an energy absorbing reaction, which makes the bottle cooler.
Why Does Water Rise? Make the water rise just using a candle and a bowl! The flame heats the inside of the container and the hot air inside the container expands quickly. When the flame goes out, the air in the container cools. The cooler air takes up less space and this creates a weak vacuum inside the container. The higher pressure is outside the container pressing down on the water in the dish. The outside air pushes water into the container until pressure is equalized.
Giant Bubbles What makes a bubble? You may know that soap is important to form one, but did you know that there is also a tiny layer of water that is vital to keeping the bubble unpopped? The bubble “pops” when that layer of water is broken. When you add glycerin to the bubble mixture, it holds onto the water and keeps it together. This added force allows the skin of the bubble to stretch even further than normal. The glycerin helps with the surface tension of your bubbles, making them “thicker” and giving them more structure so they last longer!
Goldenrod Paper Color changes can be an indication that a reaction has occurred. It also can give some hints about the type of chemicals that are causing the reaction. pH is a special property that can measure how acidic or basic a material is. The reaction between an acid pigment in the goldenrod paper and a base has been used for decades to measure this property based on colors. We will use baking soda as a base to write on the acidic paper and see your message in red.
How Does a Camera Work? At the most basic level, digital cameras today and the cameras of the past share the same basic structure - they are dark containers with a hole in one side to let in light. Can you identify where the hole/lens on a contemporary or smartphone camera is? Today, we have created our own very basic cameras out of materials you can find around your house! They are called pinhole cameras because the hole to let in the light will be the size of the tip of a pin. This activity has been adapted from Houston Center for Photography.
Disappearing Glass Rods You can make glass objects disappear completely! You see glass in air because it bends light as it passes through it. This is because when light passes from air into the glass, it actually changes speed. It’s this change in speed that causes the light to reflect and refract, allowing you to see the glass object! However, when you place the glass in something that isn’t air – something that light travels through at a similar speed – it doesn’t bend the light anymore – so you can’t see it anymore!
Long Light Exposure Tent Flood a camera with light and create fun pictures! You’re probably used to your phone camera which takes pictures really fast! In other words, it has a very fast or short “shutter speed.” Shutter speed refers to how long the camera allows light into its lens. Longexposure photography, also known as time-exposure or slow-shutter photography, involves using a long duration shutter speed. This leads to very interesting photos where any kind of motion is captured - leading to a blurry picture. We can use this to our advantage to create fun pictures!
