LUMINOR Q&A - Water Chemistry
A. The chemical description of water is H2O, which means that water is formed by the combination of two hydrogen atoms and one oxygen atom. Hydrogen atom weighs one-sixteenth of an oxygen atom, thus in water molecule, 88.8% of weight is from oxygen, while 11.2% belongs to hydrogen.A. Water has the capacity to dissolve more substances than any other liquid, thus, is called universal solvent. The universal solvent quality enables water to take other valuable minerals, nutrients or chemicals with them wherever they go. The polar bonds in water molecule make it a universal solvent.A. Substances dissolving readily in water are called hydrophilic compounds. They consist of ions or polar molecules that use electrical charge effects to attract water molecules. The water molecules surround these polar molecules and carry them into the solution, thereby dissolving them. For example, ionic substances like sodium chloride dissolve in water, as the positive sodium ions and negative chlorine ions of sodium chloride get attracted to the polar water molecules.A. Molecules with prevailing non-polar bonds are the ones that are mostly insoluble in water and are called hydrophobic compounds. Hydrocarbons containing C-H bonds are examples of hydrophobic compounds. This is because the intensity with which water molecules are attracted to C-H bonds, is far lesser than the intensity towards other water molecules. Hence, water molecules do not carry these hydrocarbons into the solution.A. The pH scale runs from 1 to 14, wherein ph 1-6 refers to acidic pH, while pH 8-14 refers to basic pH. At pH 7, a chemical is known to be neutral. The pH of a chemical substance is determined by the amount of hydrogen atoms in it. Thus, a chemical compound with high pH has higher number of hydrogen atoms in its chemical composition and are called acids. Whereas compounds with lower pH contains lower number of hydrogen atoms and are called bases. The pH of water is neutral. Read more on how to make alkaline water.A. Physical properties of a substance are properties that have everything to do with the substance's appearance. Chemical properties are properties that are often used in chemistry, to address the state of a substance. Physical and chemical properties can tell us something about the behaviour of a substance in certain circumstances.A. When substances freeze, usually the molecules come closer together. Water has an abnormality there; it freezes below 0°C, but when temperatures go below 4°C, water starts to expand again and as a result the density becomes lower. Density of a substance means the weight in kilograms of a cubic metre of a substance. When two substances are mixed but do not dissolve in one another, the substance with the lowest density floats on the other substance. In this case that substance is ice, due to the decreased density of water.A. Polarity determines if a substance is water-soluble. A polar substance is a substance that has two kinds of "poles", as in a magnet. When another substance is also polar the poles of the substances attract each other and as a result the substances mix. A substance then dissolves in water.
Substances that contain no 'poles' are called apolar substances. Oil for instance is an apolar substance, which is why oil does not dissolve in water. In fact it floats on water, just like ice, due to its smaller density.A. The answer is, "That depends?". Salt water freezes at a different temperature than fresh or pure water. The freezing temperature for salt water depends on how much salt is present in the water. The more salt there is in water, the lower the freezing temperature will be. Typical ocean water that is not close to a glacier, rivers or any kind of inlet contains about 35 g of salt per 1,000 units of water. This means that ocean salt water will freeze at about -1.91°C.A. Salt water (NaCl) freezes at a lower temperature than pure water (H20) because of its chemical properties. Normally for water to freeze, the H and O have to bond. However, the presence of salt in the water makes it harder for the H and O to bond together. The salt does not naturally bond with the ice and because the salt particles replace the water particles, the rate of freezing drops.A. The weight of a molecule is determined by the atomic masses of the atoms that it is built of. The atomic mass of an atom is determined by the addition of the number of protons and neutrons in the nucleus, because the electrons hardly weigh anything. When the atomic masses of the separate atoms are known, one simply has to add them up to find the total atomic mass of a molecule, expressed in grams per mol. Hydrogen has a relative atomic mass of 1 g/ mol and oxygen has a relative atomic mass of 16 g/ mol. Water consists of one oxygen atom and two hydrogen atoms. This means that the mass of a water molecule is 1g + 1g + 16g = 18 g/ mol.A. The weight of 1 US gallon of water is approximately 8.35 lbs (3.79 kg), while the weight of 1 Imperial gallon is approximately 4.5 kg (10.0 lbs). As a reference, the average weight of 1 US gallon of seawater is approximately 8.56 lbs (3.88 kg), while the weight of 1 Imperial gallon is approximately 4.61 kg (10.2 lbs).