When gastric hydrochloric acid reaches the nerves in the gastrointestinal mucosa, they signal pain to the central nervous system.

When the partial pressure of is reduced, for example when a can of soda is opened, the equilibrium for each of the forms of carbonate ( carbonate, bicarbonate, carbon dioxide, and carbonic acid ) shifts until the concentration of in the solution is equal to the solubility of CO < sub > 2 </ sub > at that temperature and pressure.

When LABs compete for nutrients, their metabolites often include active antimicrobials such as lactic and acetic acid, hydrogen peroxide, and peptide bacteriocins.

When jewelry containing diamonds is heated ( for repairs ) the diamond should be protected with boracic acid ; otherwise the diamond ( which is pure carbon ) could be burned on the surface or even burned completely up.

When jewelry containing sapphires or rubies is heated, it should not be coated with boracic acid or any other substance, as this can etch the surface ; they do not have to be " protected " like a diamond.

When ionized hydrogen is written as " H < sup >+</ sup >" as in the solvation of classical acids such as hydrochloric acid, the hydronium ion, H < sub > 3 </ sub > O < sup >+</ sup >, is meant, not a literal ionized single hydrogen atom.

When later adapted by Carl Auer von Welsbach for the splitting of didymium, nitric acid was used as a solvent to lower the solubility of the system.

When dissolved in hydrochloric acid, a water-soluble yellow salt, PmCl < sub > 3 </ sub >, is produced ; similarly, when dissolved in nitric acid, a nitrate results, Pm ( NO < sub > 3 </ sub >)< sub > 3 </ sub >.

When the tRNA has an amino acid linked to it, it is termed " charged ".

When treated with potassium fluoride and hydrofluoric acid, Th < sup > 4 +</ sup > forms the complex anion, which precipitates as an insoluble salt,.

When baking soda and vinegar are combined, the bicarbonate ion of the baking soda is turned into carbonic acid, which decomposes into carbon dioxide and water.

When it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide from its muscles directly to its stomach ; the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone.

When standardized, it is done so as a percentage of valerenic acid or valeric acid.

When the biological significance of nicotinic acid was realized, it was thought appropriate to choose a name to dissociate it from nicotine, to avoid the perception that vitamins or niacin-rich food contains nicotine, or that cigarettes contain vitamins.

When a lead – acid battery is charged or discharged, this initially affects only the reacting chemicals, which are at the interface between the electrodes and the electrolyte.

When that mixture has dried, the metal stylus is used on the plate and thereby removes some of the grit particles, so that minuscule areas of copper are exposed to the acid and etched ; they will eventually hold the ink for the printing process.

When jewelry containing rubies is heated ( for repairs ) it should not be coated with boracic acid or any other substance, as this can etch the surface ; it does not have to be " protected " like a diamond.

When he was eight years old his father gave him a large chemistry set which was enhanced over the next few years with extra chemicals including a bottle of concentrated sulphuric acid, bought from a pharmacy, at a time when pharmacists were less regulated than now.

When these cytokine factors bind, the arachidonic acid pathway is then activated.

When some strong acid is added to an equilibrium mixture of the weak acid and its conjugate base, the equilibrium is shifted to the left, in accordance with Le Chatelier's principle.

When carbon dioxide dissolves in water it exists in chemical equilibrium producing carbonic acid:

A 2007 USDA comparison between steaming and boiling vegetables shows the most affected nutrients are folic acid and vitamin C. When compared to raw consumption, steaming reduces folic acid by 15 %, and boiling reduces it by 35 %.

When covalent bonds link long chains of atoms in large molecules, however ( as in polymers such as nylon ), or when covalent bonds extend in networks though solids that are not composed of discrete molecules ( such as diamond or quartz or the silicate minerals in many types of rock ) then the structures that result may be both strong and tough, at least in the direction oriented correctly with networks of covalent bonds.

When the molecules collide, they transfer energy to each other in varying degrees, based on how they collide.

When only a small proportion of the molecules meet these criteria, the rate of evaporation is low.

When they are not attached to other molecules, they are known as " free " fatty acids.

When the electric current is applied, the larger molecules move more slowly through the gel while the smaller molecules move faster.

When exposed to the atmosphere, zinc reacts with oxygen to form zinc oxide, which further reacts with water molecules in the air to form zinc hydroxide.

When the brown solution of iodine in strong donor solvents were heated, a color transition from brown to violet is observed as the weakly-bonded charge-transfer complex dissociates into to free solvent and iodine molecules.

When EMR interacts with single atoms and molecules, its behaviour depends on the amount of energy per quantum it carries.

When dissolving a lipophilic or amphiphilic substance in a polar environment, the polar molecules ( i. e., water in an aqueous solution ) become more ordered around the dissolved lipophilic substance, since the polar molecules cannot form hydrogen bonds to the lipophilic areas of the amphiphile.

When an external electric field is applied to the liquid crystal, the dipole molecules tend to orient themselves along the direction of the field.

When a magnetic field is applied, the molecules will tend to align with or against the field.

Effect of a magnet on the domains. When a domain contains too many molecules, it becomes unstable and divides into two domains aligned in opposite directions so that they stick together more stably as shown at the right.

When a magnetized ferromagnetic material is heated to the Curie point temperature, the molecules are agitated to the point that the magnetic domains lose the organization and the magnetic properties they cause cease.

When the Ag < sup >+</ sup > ion forms a complex with these molecules, they are rendered unusable by the bacteria, depriving them of necessary compounds and eventually leading to their death.

When activated, toll-like receptors ( TLRs ) take adapter molecules within the cytoplasm of cells in order to propagate a signal.

When a signal comes down an axon, the synaptic vesicles fuse with the cell membrane releasing the neurotransmitter so that it can be detected by receptor molecules on the next nerve cell.

When a small sub-molecular imperfection was introduced into Captain America's shield, each impact over the years spread to neighboring molecules.

When air molecules collide, they also bounce away from each other ( a restoring force ).

When relatively dry dough is worked by kneading, or wet dough is allowed to rise for a long time ( see no-knead bread ), the glutenin forms strands of long, thin, chainlike molecules, while the shorter gliadin forms bridges between the strands of glutenin.

When something is dissolved, molecules of the solvent arrange themselves around molecules of the solute.

When heat radiates from the surface of the earth, it is released as long-wave radiation, which can move freely through gases composed of diatomic molecules ( such as the atmosphere's oxygen and nitrogen ), but is readily absorbed by triatomic molecules, such as carbon dioxide and water vapor.