Chemistry – a Sequence of Experiments

In our class, we did four weekly sessions on chemistry: States of Matter, Mixtures & Solutions; Reactions; More Reactions.

Another way to approach chemistry would be as a sequence of experiments, either done all in a row in a single session, or one experiment per day for several days running, or whatever. These start with a basic concept, then build on it.

Oil and Water (Immiscible Substances)

  • Concept 1: Water will combine with water. Oil will combine with oil.
    • Take two containers. Put water in each. Then pour the two containers together. They mix – water likes water. (To make this more interesting: Color one container yellow with food coloring or liquid watercolors. Color the other blue. Then mix them together – they immediately intermingle, and make green.)
    • Take two containers. Put vegetable oil in each. Use a food coloring that will combine with oil, such as Americolor Candy Oil. Color one container one color, and the other a different color. Mix the two container together – they immediately intermingle.
  • Concept 2: Oil and water don’t combine. Pour water in a jar or clear container. Gently pour in some oil.  (Can re-use water and oil from experiment above.) Do they mix? No. Explain why. (For a 3 or 4 year old, you just say some substances don’t like each other, and won’t mix together. For older children, you can get into more of the scientific detail about positively and negatively charged molecules)
    • You can point out that the oil always floats to the top, because it’s “lighter weight” or less dense. (Again, the older the child you’re working with, the more sophisticated your description of density can be.)
    • Put a lid on the container, and gently pour it back and forth, making “waves.”
    • Shake the container really hard – can you mix the oil and water? At first, it might look like you have…
    • Then set the container down and watch what happens. The small bubbles of water find each other, and grab hold of each other and sink toward the bottom. The small bubbles of oil grab each other and float to the top. Pretty soon, you have your two layers back again.
  • Concept 3: Oil and water-based things don’t mix
    • In one container, pour a small amount of oil. Then drip in either food coloring or liquid watercolor. Explain that these are colors mixed with water. Will they mix with the oil? No. Take a fork or whisk and beat them together (or seal the container, and shake it lots.) Did they mix? Nope – just made lots of little bubbles of colored water in the oil. Kids can use toothpicks to push the little bubbles together – they grab hold of each other and make bigger bubbles in the oil
  • Experiment 4: “Fireworks in a Jar”
    • Put some water in a see-through container. In another container, mix together oil and water-based coloring (you can re-use your mixture from concept 3 experiment. Then gently pour the oil on top of the water. The food color bubbles gradually sink through the oil. When they hit the water, the color will disperse through the water. To see pictures of this in action, just search for “fireworks in a jar.”
  • Experiment 5: “Lava Lamps”
    • You can use your “fireworks in a jar” mixture for this (or make a new container of colored water and oil.) Then add an Alka-Seltzer tablet (or some table salt). It will create bubbles, which carry the colored water up through the oil, then it pops and they sink back down, etc. To see pictures of this experiment, just search for “lava lamps kid science”.
  • Experiment 6: At some point, you’ll be cleaning up. If your child got oil on their hands, you can have them wash their hands with just cold water. When they’re done washing, show them that their hands are still oily. Now wash again with soap. Now the oil is gone. Why? The soap helps the oil and water combine, and the water rinses away the oil. (Science of this described here.)
  • Experiment 7: Take a container with oil and water in it. Shake it to show they won’t mix. Now add some liquid hand soap or detergent. Shake it. They’ve combined. (Learn about the science here.)  Soap is an emulsifier. It helps oil and water stay combined.
  • Experiment 8: Vinegar and oil don’t mix either.
    • Do an experiment like concept 2, except with vinegar and oil.
  • Experiment 9: A Jar of Bubbling Goo. (See more details here.)
    • Make baking soda ice cubes. Fill a container with an inch of vinegar and an inch or two of oil. (You can re-use your mixture from experiment 8.) Drop in a baking soda ice cube, and watch it bubble and ooze.
  • Experiment 10: An emulsifier can connect vinegar and oil
    • Beat together oil and vinegar – they won’t stay combined. Add an egg yolk. Beat with an electric mixer… for a while, nothing happens, then suddenly, it will turn into a mayonnaise like substance – the egg yolk is the emulsifier which holds the oil and vinegar together.
    • You can also make real home-made mayo (find recipes online).

Acids and Bases

Introductory Experiments:

  • Taste: give your child a spoonful of lemon juice or lemonade. Ask them to describe the taste – is it sour? Then give a spoonful of milk? Is that sour? No. Acidic things taste sour, base things do not.
  • Smell: Have them smell lemon juice and vinegar – strong smell wrinkles up their nose. Have them smell milk, and soapy water or bleach water – milder smell.
  • Feel: make small dishes full of vinegar, lemon juice, soapy water, and bleach water. Have them try rubbing the fingers of their left hand in the vinegar and lemon juice, and the fingers of their right hand in the soapy water or the bleach water. The base items (soap and bleach) make their fingers slippery.

Reactions:

  • Baking soda and vinegar react. Mix some together in a dish. Observe the reaction. What do you notice? (Fizzy sound and foam.)
    • you can also cover a shallow tray with baking soda, then mix vinegar and food color or liquid watercolor and let them drip the vinegar on the baking soda with pipettes
  • When baking soda and vinegar react, they create a gas. Do the self-inflating balloon experiment described here. Explain that the reaction is creating a gas which is filling the balloon.
  • When gasses expand they can fill a space. You could put vinegar and baking soda inside a test tube with a stopper or a bottle with a cork. As the gas expands, the container will blow its top.
  • Make Ziploc time bombs: www.geeksraisinggeeks.com/quick-science-experiments/
  • Make baking soda ice cubes (make a paste of baking soda and water, freeze it.) Then drop one in a container of vinegar for a “time release” reaction
    • Then put oil and vinegar in a jar with some food coloring. Add a baking soda ice cube for a jar of bubbling goo (see video here.)
  • It’s not just baking soda and vinegar that react – most acids and bases will react
    • Do erupting lemons experiment described here
    • Curdle milk (a base) with lemon juice (an acid). Then make milk plastic with it, as described here

Testing for Base vs. Acid

  • There are multiple ways to test whether a substance is acid or base. You could, of course, use litmus paper or ph paper.
  • You can also make an indicator using red cabbage. Learn more here or here.
  • Or you can make an indicator with turmeric
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