Nitya Jain, PhD, is a Mass General researcher from the Mucosal Immunology and Biology Research Center. Her lab focuses on understanding how the immune system develops and operates in newborns to help develop new approaches to improve the health of infants around the world.
When the COVID-10 pandemic began, Dr. Jain started working from home with her two young children, and she decided to both challenge herself and promote STEM learning by conducting a new science experiment every day with her children.
Fast forward 11 weeks and four days later and she is still going strong!
Follow her on Twitter to see her daily “STEM in the time of COVID” updates and be sure to check out parts one and two of her experiments in our previous posts!
Density Column
What you need:
- 1 cup of each of the following liquids:
- Honey
- Dish Soap
- Water
- Sugar water (1 cup warm tap water + ¼ cup sugar- stir well to dissolve the sugar)
- Vegetable oil
- Rubbing alcohol
- Food coloring
- Tall, clear (preferably narrow) glass to make your column in (we used a white wine glass)
Activity:
- Measure a cup (~10oz) of each liquid into plastic cups.
- Add a few drops of food coloring to the water, sugar water and rubbing alcohol.
- Start your column by pouring the honey into the glass. Pour it very slowly into the center of the glass without letting the liquid touch the sides. Allow layer to ‘settle’ before adding the next one.
- Next pour any one of the other liquids in — this time pour slowly allowing the liquid to touch the sides of the glass. Be careful with the dish soap- you want to go slow and not make bubbles. Again, allow each layer to ‘settle’ before adding the next one.
- You’ll note that a liquid may settle between two layers — for example, if you have poured oil onto your column and are now pouring the water, you will see that the water slides underneath the oil and forms a layer below it.
- Pour each liquid and observe your beautiful column of stacked liquids.
How does it work?
Each liquid used here has a unique density. Density is a measure of how much mass is contained in a given unit volume (density = mass divided by volume).
If mass is a measure of how much “stuff” there is in an object or liquid, density is a measure of how tightly that “stuff” is packed together.
Lighter liquids (like water or rubbing alcohol) are less dense or have less “stuff” packed into them than heavier liquids (like honey or sugar water) and will settle above the denser liquids.
To take this activity one step further, select a few items from around the house (small Lego or ball, raisin, staple, safety pin, etc.). Drop each item one at a time onto your column and note where they float. Some will stay on or near the top of stacked liquids, some will sink part or all the way down depending on their own density.
Lava Lamp
What you need:
- 1 empty 500ml plastic water bottle
- Water
- Oil
- Food coloring
- Alka-Seltzer tablets
Activity:
- Fill the bottle about a quarter of the way with water.
- Pour vegetable oil into the bottle until its almost full.
- Add several drops of food coloring (we used red) — watch as the color sinks through the oil into the water layer.
- Wait a few minutes for the oil and water to separate fully.
- Break an Alka-Seltzer tablet into a few pieces and drop them into the bottle one at a time.
- Watch the lava lamp get activated!
How does it work?
Oil and water do not mix (water is a polar solvent while oil is non-polar). Oil also has a lower density than water and always floats above the water. The Alka-Seltzer reacts with water to make tiny bubbles filled with the gas, carbon dioxide.
The bubbles attach to blobs of colored water and cause them to rise through the oil to the surface. When the bubbles pop, the color blob sinks back to the bottom of the bottle. This process keeps going until all the Alka-Seltzer is used up.
Color changing milk
What you need:
- 1 cup of whole milk
- A bowl or saucer
- Food coloring
- Cotton swab/Q-tip
- Liquid dish soap
Activity:
- Pour milk into the bowl to a depth of about half an inch. Allow milk to settle.
- Add drops of food coloring to the milk. Keep the drops close together in the center of the bowl of milk.
- Wet a cotton swab in liquid dish soap. Touch the soapy end of the swab to the surface of the milk in the middle of the bowl. Hold it there for about 10-15 seconds. Watch the colors spread out from the center!
How does it work?
Milk is made up of mostly water but also contains vitamins, minerals, proteins and tiny droplets of fat. The milk fat is non-polar, meaning these molecules do not mix in water.
When dish soap is added to the surface of milk, the detergent in the soap forms a structure called micelles with the water molecules in milk. Micelles are spherical structures containing water-loving (hydrophilic) portions on the outside and water-repelling (hydrophobic) portions on the inside (in the core of the sphere).
The hydrophilic part of the soap molecule sticks to the water in milk trapping hydrophobic non-polar milk fat molecules in the middle. As the soap molecules race around to join up with more fat molecules, the food coloring gets bumped and shoved everywhere, which is what you observe.
Try the same activity with low-fat or 2% milk and see how it compares with whole milk. Remember, it is the fat content in the milk that gives the dramatic ‘burst’ of color!
Elephant’s toothpaste
What you need:
- 40-volume hydrogen peroxide (can be found in salon stores)
- A tall bottle (1-litre soda bottle will work)
- 1 dry active yeast packet (e.g. Fleischmann’s)
- Dish soap
- Food coloring
Activity:
- Add ~120ml of 40-volume hydrogen peroxide to the 1-litre soda bottle.
- Add a couple of squirts of dish soap and swirl the solution to mix the contents.
- Add food coloring into the bottle by allowing drops to slide down the sides of the bottle (this will make stripes on the wall of the bottle).
- Activate the yeast by mixing an entire package of dry yeast with 4 tablespoons of very warm water in a cup. If the mixture is too thick, add some more water to thin it out.
- Pour the entire yeast mixture into the bottle and watch!
How does it work?
The yeast contains an enzyme called catalase that breaks down the hydrogen peroxide into water (H2O) and oxygen (O2). The oxygen (which is a gas) forms millions of tiny bubbles in the dish soap which rise up the bottle to come out as foam. The bottle also feels warm to the touch because this enzyme reaction is exothermic- that is, energy in the form of heat is given off.
Rising water
What you need:
- Shallow dish (1/2 inch depth)
- Water
- Food coloring
- A glass milk bottle or other comparable glass bottle
- Candle
Activity:
- Add a few drops of food coloring to a glass of water.
- Pour colored water into the shallow dish.
- Place the candle straight up in the center of the plate. Test if your glass milk bottle will fit over the candle. Also, make sure the base of the bottle is well above the candle wick and its top edge is submerged under water. If necessary, add more water. If the setup looks good, remove the bottle.
- Make sure the candle is stable, and the water still. Light the candle and allow to burn brightly.
- Turn the milk bottle over and lower it slowly over the burning candle. Place the bottle upside down in the dish with water. Keep a close eye on the water level inside the bottle.
- The candle remains burning for a short bit and the water level rises slowly. As soon as the candle goes out, the water level rises quickly.
How does it work?
The consumption of oxygen by the flame in the bottle is not the reason the water rises! At first, the burning flame heats up the air inside the bottle causing the air to expand quickly. Some of this air escapes from under the bottle (you may have noticed bubbles coming out initially when you placed the bottle in water).
When the flame goes out, the air inside the bottle cools and cooler air contracts. This creates a weak vacuum or low pressure inside the bottle. As the air pressure is higher outside the bottle, the water from outside is pushed into the bottle. The water level inside the bottle keeps rising until the pressure is equalized inside and outside the bottle.
Color changing flowers
What you need:
- Flowers: White tulips or carnations
- Flower vase
- Food coloring
- A lot of patience!
Activity:
- Trim down the stem (about 1 inch) of a white tulip or carnation (we used tulips)
- In a flower vase, pour water and add several drops of food coloring
- Place the flower in the vase and observe the petals over 24-48 hours.
How does it work?
The water travels up the stems of flowers in ‘elevators’ called the xylem. The colored water allows us to observe the capillary action that pulls water up against gravity into the petals and leaves.
COVID-19 Research at Mass General
Researchers and clinicians at Massachusetts General Hospital Research Institute are mobilizing to develop new strategies to diagnose, treat and prevent COVID-19. Learn more.
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