Chemical omelette

Turn an egg white yellow!

Difficulty:
Danger:
Duration:
20 minutes
Chemical omelette

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

I still have the egg white from the last experiment. Can I use it?

Sure! One egg white may well be enough for all three experiments in this set.

How should I separate the egg white from the yolk?

There are several ways to separate the egg white from the yolk. Choose the one you like best!

First, you may already have a special tool for this at home. Ask your supervising adult about it, and use it if you do in fact have it!

If you don't have such a device, don't worry! Ask your supervising adult to use a sharp knife to break the egg over the plastic cup. Let the egg white drain, shifting the yolk from one half of the shell to the other.

You can also ask your supervising adult to hold the egg vertically and bore a small hole in the top using a needle or the tip of a sharp knife. Hold the egg upside down over a plastic cup and make an even smaller hole at the other end. Wait until all the egg white leaks out, then crack the egg normally over another container to deposit the yolk.

Also, if you have a clean, empty plastic bottle close by, you can use it to separate the egg white from the yolk. First, crack the egg into a plastic cup. Then, squeeze the bottle to force most of the air out of it. Third, bring the neck of the bottle to the yolk and stop squeezing the bottle. The yolk should be sucked into the bottle.

The contents of the test tube aren’t turning yellow. What should I do?

This experiment requires boiling water, so it’s a good idea to first try replacing your water with hotter water. Leave the test tube for 10 minutes.

If this doesn't work, try mixing the contents of the test tube with a wooden stick and leaving the test tube in the boiling water for 10 more minutes.

If the contents still don’t turn yellow, try repeating the experiment.

Can I use one spoon to measure all of the reagents?

The experiment might not turn out quite right if you measure all of the reagents using one spoon. We recommend either using different spoons, or washing and drying your spoon before each new reagent.

Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with an excess of water.

Scientific description

Proteins are extremely diverse—there are millions of different kinds of them. All proteins, however, are made of only 22 different building blocks known as amino acids. Four of these amino acids are "aromatic,” meaning that they contain special "rings" of atoms . These react with the nitric acid you obtained in your experiment to produce yellow compounds.

When a reaction produces a clearly-visible result, such as the yellow color in the reaction between nitric acid and a protein, it can be used as a qualitative test. In other words, it can help determine if a sample contains the compound in question. The egg white in your vial turned yellow—and in addition to simply being cool, this lets you conclude that it did indeed contain proteins with aromatic amino acids.

What happens to the egg white?

Chemically, an egg white is made out of protein molecules. Proteins are very large molecules with a complex structure. Proteins are made of many individual amino acids. The individual amino acids are linked together to form chains. These chains are twisted together into a complex spiral or knot. However, as soon as a molecule of protein meets with a molecule of nitric acid HNO3 – this complex structure starts to unwind and forms a yellow-colored yolk-like mass. This is how an egg white “turns into a yolk”. This experiment is very practical. Chemists use this reaction to determine the presence of protein in different samples. It is called the xanthoproteic test.

How is nitric acid produced in this experiment?

Nitric acid forms when we mix sodium hydrogen sulfate with calcium nitrate, according to the following reaction:

NaHSO4 + Ca(NO3)2 → CaSO4 + NaNO3 + HNO3