Fire foam

• 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.

• 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.

• 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.

A reaction of zinc with acids is a common method for obtaining hydrogen in a laboratory. There is even a special instrument for conducting such chemical reactions – Kipp’s apparatus, which has been invented in the middle of 19th century.

Generally speaking, Kipp’s apparatus is an “advanced” version of a system we use in our experiment. When hydrogen is being synthesized in a Kipp’s apparatus, granulated zinc in the middle reservoir reacts with concentrated hydrochloric acid (HCl) or diluted sulfuric acid (H₂SO₄). This process produces hydrogen gas. Next, hydrogen is released via a lateral outlet with a valve on it, to the outside where it can be collected and routed for further use.

An advantage of a Kipp’s apparatus, compared with our hydrogen production setup, is that we could close the valve to stop the reaction: released hydrogen pushes acid out of the middle reservoir, and the reaction cannot proceed. When the valve is opened, the process starts over again.

Interestingly, a principle of Kipp’s apparatus is based on a design of Döbereiner’s lamp, the first real lighter. In a Döbereiner’s lamp, a zinc plate reacts with sulfuric acid yielding hydrogen that accumulates in an airtight vessel. When a valve is open, the gas is rushed to the outside where it passes through a porous platinized asbestos plate. The latter initiates ignition of hydrogen in air: metallic platinum Pt dissolves hydrogen and promotes its reaction with oxygen. Finally, when the valve is closed, the gas accumulates in the vessel and pushes the acid away from zinc, thus, ceasing the reaction.

Kipp’s apparatus can also be used for obtaining other gases, for example, carbon dioxide CO₂. In this case calcium carbonate CaCO₃ reacts with diluted acid (for example, hydrochloric acid HCl), giving carbon dioxide CO₂ and calcium chloride CaCl₂.

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑

You can see how this reaction is performed with the help of Kipp’s apparatus in the video below.

A hydrogen bond is called so because of hydrogen that participates in this kind of interaction. Importantly, a participating hydrogen atom must already have a polar bond with another element, such as oxygen (“O–H” bond) or nitrogen (“N–H” bond). A polar bond is a bond formed by two different elements, one of which withdraws electrons towards itself stronger than the other. Here, “O–H” and “N–H” bonds are a classic example, where oxygen and nitrogen “pull” the electrons. So, the second participant of a hydrogen bond is usually a nitrogen or oxygen atom (and sometimes fluorine). Moreover, these atoms must also be a part of a molecule where they already participate in a polar bond. Finally, when all of the criteria are met, these potential participants form hydrogen bonds between each other.

These hydrogen bonds are about twice longer than bonds interconnecting atoms within a molecule. Subsequently, it takes roughly 10 times less energy to break a hydrogen bond than to break, for instance, an “O–H” bond in a water molecule.

Hydrogen bonds are formed not only between adjacent molecules. Indeed, thanks to this type of interaction, life on Earth is possible as it is today. It isn’t just about keeping water in a liquid state that prevents oceans from evaporating. In all living organisms, any protein can only work when its molecule, which consists of long chains of atoms, is folded into its correct geometrical shape. And it is hydrogen bonds that form between the sections of this chain to help them “roll” into proper configurations. Moreover, hydrogen bonds play a key role in formation of a DNA structure, the main carrier of information in a living organism.

In our experiment, glycerin is needed to form three (!) hydrogen bonds to make liquid more viscous. Thanks to increased viscosity, bubble walls become less “runny,” which in turn makes bubbles last longer.

Using glycerin, we can make a composition for blowing big and quite stable soap bubbles. To do so, simply mix dishwashing liquid or liquid soap with water and glycerin. Keep experimenting with ingredients ratio to create huge bubbles! Keep in mind, though, that moderation is more satisfying than excess: amount of glycerin added should not exceed 10% by volume. When too much glycerin is added, the resulting liquid will be too thick and viscous, making it hard to work with, and the bubbles will be heavy and fragile.

Perhaps, you’ve heard about oxyhydrogen or “knallgas,” which means “bang-gas.” It’s a mixture of 2:1 mixture of hydrogen and oxygen. When mixed at this exact ratio and then ignited, these gases react instantly with explosion due to release of enormous amount of heat. Because of this heat, which is swiftly transferred to the gas, the latter promptly expands in a reaction zone forming an explosion wave.

Due to a high risk of detonation, any work with air-hydrogen and oxygen-hydrogen mixtures requires wearing safety glasses and a presence of a second person to provide help if needed. In our case, however, the volumes are too small to worry about. There is no danger to an experimenter. Nevertheless, do observe common safety rules: put away flammable materials and work with open fire carefully.

However, if you still want to know what will happen in case of explosion of higher volumes of hydrogen, for example, a hydrogen filled balloon, watch the video below! But remember: never repeat it at home!