Disappearing powder

Ammonium carbonate disappears when heated!

Difficulty:
Danger:
Duration:
5 minutes
Experiment's video preview
Chemical formula

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Keep a bowl of water nearby during the experiment.
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

During the experiment, it smells unpleasant. This is not dangerous?

Ammonia carbonate decomposes into carbon dioxide, water and ammonia. And ammonia is exactly what we can smell! It is released in small amounts in this experiment, such concentration is quite safe. By the way, aqueous ammonia is a known medicament, it's often used to revive fainting people.

Step-by-step instructions

Step-by-step instructions
  1. Set the candle onto the fuel tablet stove as shown. Light the candle.
  2. Set the flame divider onto the stove and place the foil on top of it.
  3. Pour out 1 big spoon of ammonium carbonate (NH4)2CO3 onto the center of the foil sheet.
  4. Watch how the powder gradually disappears. It will take 2 – 3 minutes for ammonium carbonate to disappear completely.

Graphical step-by-step instruction

Expected result

When heated, ammonium carbonate decomposes into three gaseous products: ammonia, carbon dioxide, and water vapor. All three substances blend with the surrounding air, so the powder disappears!

Disposal

Dispose of the experiment residues along with regular household trash.

Scientific description

What happens with ammonium carbonate?

At elevated temperatures, ammonium carbonate (NH4)2CO3 decomposes into its subcomponent substances: ammonia NH3, carbon dioxide CO2, and water H2O:

(NH4)2CO3 → 2NH3(gas) + CO2(gas) + H2O(gas)

NH3 and CO2 are both gases. Water (even though liquid at room temperature) rapidly evaporates when heated. That is why in just a few minutes ammonium carbonate powder disappears leaving nothing but memories.

Learn more

Ammonium carbonate is an unstable compound. When stored it gradually releases ammonia and transforms into ammonium bicarbonate NH4HCO3:

(NH4)2CO3 → NH4HCO3 + NH3(gas)

During thermal decomposition, ammonium bicarbonate behaves the same way as carbonate. The only difference is that it releases less gas:

(NH4)HCO3 → NH3(gas) + CO2(gas) + H2O(gas)

What other solid substances behave similarly?

Many compounds can "disappear" when heated, but not all of them undergo decomposition.

Learn more

Numerous substances undergo thermal decomposition, but only few of them decompose without leaving a solid residue. One of examples would be oxalic acid C2O4H2 that decomposes into gaseous compounds, similarly to ammonium carbonate:

C2O4H2 → CO2(gas) + CO(gas) + H2O(gas)

When heated, most substances melt and only then evaporate. However, some compounds can skip the melting step. Direct conversion of solids into gas without their decomposition is called sublimation. Easily sublimated substances include, for example, crystalline iodine (I2) and benzoic acid (C6H5COOH).

disappearing_powder_phase_eng_1

Keep in mind that oxygen of the ambient air is not involved in sublimation and thermal decomposition processes. However, if a substance being heated "evaporates" due to its interaction with atmospheric oxygen, it is a usual reaction of oxidation.

An interesting process occurs when ammonium chloride NH4Cl is heated. At elevated temperatures, it easily decomposes into ammonia NH3 and hydrogen chloride HCl. However, as soon as these gases cool down, they immediately react with each other forming their precursor:

NH4Cl <=> NH3 + HCl

Hence, in this case, a thermal decomposition process may very well be mistaken for a sublimation process.

Taking copper salts as an example, consider the following thermal decomposition reactions. Not all of their products are gaseous:

Copper formate: Cu(HCOO)2 → Cu + H2O(gas) + CO(gas) + CO2(gas)

Copper nitrate: 2Cu(NO3)2 → 2CuO + 4NO2(gas) + O2(gas)

Now it is clear that ammonium carbonate is just one of many substances that may be used in a thermal decomposition experiment. The choice of this particular material is determined by its safety for home experiments.

Follow up

Hunt for water

You can conduct an interesting experiment using ammonium carbonate powder. As you may already know from the scientific description of the experiment, (NH4)2CO3 undergoes thermal decomposition yielding ammonia, carbon dioxide, and water:

(NH4)2CO3 –> 2NH3(gas) + CO2(gas) + H2O

Moreover, when heated on an aluminum foil, water “disappears,” too. But it can be caught! Before you carry out the experiment, prepare the beaker from the starter kit. Make sure it is clean and dry. Follow the first three steps of the instructions. As soon as you pour out all the ammonium carbonate on the foil, carefully cover it with the beaker turned upside down, so that all the (NH4)2CO3 powder is trapped inside the glass. Observe the bottom of the beaker closely. Soon, there will accumulate small droplets of liquid—water!

The trick is that water evaporates when heated. It rushes up and bumps into the cold bottom of the beaker. There, it has no choice but to condense, forming droplets. Therefore, the beaker acts as a trap for water.

That's interesting!

Where is ammonium carbonate used?

Thanks to its property to completely decompose into gaseous products when heated, ammonium carbonate (NH4)2CO3 found its wide application in food industry. Within nutritional supplements classification, it is referred to as E503 and is permitted for use nearly worldwide. We usually call it a baking powder. For centuries, bakeries used yeast to achieve porous structure of bread and buns. Further, chefs used a cream of tartar (tartaric acid salts mixture). Our mothers and grandmothers use a regular baking soda Na2CO3. Most modern recipes for cookies, cakes, and pies call for ammonium carbonate. The main advantage of ammonium carbonate over other baking powders is that it fully decomposes during baking process without affecting the taste of a final product.

Food industry is not the only field of application for ammonium carbonate. Most of it is used as a feedstock for production of ammonium sulphate (NH4)2SO4 from gypsum CaSO4:

(NH4)2CO3 + CaSO4 → (NH4)2SO4 + CaCO3

Resulting ammonium sulfate is used as a nitrogen-sulfur fertilizer that accelerates plants growing without saturating the soil with hazardous nitrates.

How is ammonium carbonate produced?

The process observed in the experiment is a reverse of an industrial ammonium carbonate synthesis process. To synthesize this salt, a mixture of ammonia, carbon dioxide, and water vapor is prepared. These components are heated, and the reaction products are rapidly cooled down. The main product of this reaction is ammonium carbonate:

2NH3 + CO2 + H2O → (NH4)2CO3(solid)