Amorphous:
A term that refers to a solid lacking a crystalline structure. Although there may be some local arrangement of atoms or molecules within an amorphous solid, there is an absence of long-range order.
Examples include window glass and polystyrene.
Atomic mass unit:
An atomic mass unit, abbreviated as amu, is defined as one twelfth of the mass of an unbound carbon-12 atom. This unit of mass is utilized to represent atomic and molecular masses. It is also referred to as the unified atomic mass unit (u), Dalton (Da), or universal mass unit.
Boiling Point:
The boiling point refers to the temperature at which the vapor pressure of a liquid matches the external pressure acting on the liquid. Consequently, the boiling point of a liquid is influenced by atmospheric pressure. As the external pressure decreases, the boiling point also decreases.
Buffer:
A buffer is a solution that consists of either a weak acid along with its salt or a weak base together with its salt, which exhibits resistance to variations in pH.
Examples include blood, TRIS buffer, and phosphate buffer.
Calibration:
The procedure for establishing the connection between the output or response of a measuring device and the corresponding input value. Calibration generally requires the application of a measuring standard.
Concentration:
The amount of a substance per defined space. Concentration usually is expressed in terms of mass per unit volume.
Examples: g/cm3, kg/l
Colloid:
A type of homogenous mixture in which the dispersed particles do not settle out.
Examples: Butter, milk, smoke, fog, ink, paint
Density:
Mass per unit volume. Examples: The density of pure water is defined to be 1 gram per milliliter.
Element:
A chemical element is a substance that cannot be broken down by chemical means. Elements are defined by the number of protons they possess.
Proton:
A component of an atomic nucleus with a mass defined as 1 and a charge of +1. The nucleus of a hydrogen atom. The H+ ion.
Neutron:
The neutron is the particle in the atomic nucleus with a mass =1 and charge = 0.
Electron:
An electron is a negatively charged particle within an atom. Electrons are found outside and encircling the nucleus of the atom. Each electron possesses a single unit of negative charge and has a significantly smaller mass in comparison to that of a neutron or proton.
Freezing point depression:
The occurrence in which the freezing point of a liquid (specifically a solvent) is diminished by the introduction of an additional compound, resulting in a solution that possesses a freezing point lower than that of the pure solvent. For instance, the freezing point of seawater or typical saltwater is reduced compared to the freezing point of pure water.
Glass:
An amorphous solid. The term is typically used for inorganic solids rather than plastics or other organic materials. Glasses lack a crystalline internal structure. Generally, they are hard and brittle solids. Examples include borosilicate glass, soda lime glass, and isinglass.
Gram:
A metric system unit of mass that corresponds to the mass of one cubic centimeter of water at 4°C.
Gram molecular mass:
The mass, measured in grams, of a single molecule of a molecular substance. For instance: The molecular mass of N2 is 28, which means the gram molecular mass of N2 is 28 g.
Litmus paper:
Filter paper that has been processed with a natural water-soluble dye derived from lichens. The resulting product, known as ‘litmus paper’, serves as a pH indicator. Blue litmus paper changes to red in acidic environments (pH below 4.5), whereas red litmus paper shifts to blue in basic environments (pH above 8.3). Neutral litmus paper exhibits a purplish color.
Mass:
Mass is the property which reflects the quantity of matter within a sample. Examples: 10 grams, 55.4 kg
Measurement:
Measurement is collection of quantitative data. A measurement is made by comparing a quantity with a standard unit. Since this comparison cannot be perfect, measurements inherently include error.
Mole:
A chemical mass unit, defined to be 6.022×1023 molecules, atoms, or some other unit. The mass of a mole is the gram formula mass of a substance. Examples: 1 mole of NH3 has 6.022 × 1023 molecules and weighs about 17 grams. 1 mole of copper has 6.022 × 1023 atoms and weighs about 63.54 grams.
Molecule:
A molecule refers to two or more atoms which have chemically combined to form a single species. Examples: Examples of molecules include water H2O, oxygen, gas, O2.
Molecular weight:
Molecular weight is a measure of the sum of the atomic weights of the atoms in a molecule. Molecular weight is often used interchangeably with molecular mass in chemistry, but there is a difference between the two. Molecular mass is a measure of mass and molecular weight is a measure of force acting on the molecular mass.
Mixture:
Two or more substances which have been combined such that each substance retains its own chemical identity.
Molarity:
A concentration unit, defined to be the number of moles of solute divided by the number of liters of solution. Examples: There are 6 moles of HCl in 6 molar HCl or 6M HCl
PPM:
PPM stands for parts per million. It is commonly used to express concentration and temperature coefficients. Also Known As: parts per million Examples: 100 ppm is identical to 0.01%.
Reference standards:
USP’s official Reference standards are highly characterized specimens of drug substances, excipients, impurities, degradation products, dietary supplements, compendial reagents, and performance calibrators. They are specified for use in conducting official USP-NF tests and Assays.
Solution:
A solution is a homogenous mixture of two or more substances. A solution may exist in any phase. Solution Examples: An example of a solid solution is brass. An example of a liquid solution is aqueous hydrochloric acid (HCl in water).
Solvent:
The component of a solution that is present in the greatest amount. It is the substance in which the solute is dissolved. Examples: the solvent for seawater is water. The solvent for air is nitrogen.
Specific weight:
Weight per unit volume of a material. Also Known As: unit weight
Solubility:
The maximum quantity of a substance that may be dissolved in another. The maximum amount of solute that may be dissolved in solvent.
Standard Solution:
Any solution which has a precisely known concentration. Similarly, a solution of known concentration has been standardized.
Stock Solution:
A stock solution is a concentrated solution that will be diluted to some lower concentrated for actual use. Stock solutions are used to save preparation time, conserve materials, reduce storage space, and improve the accuracy with which working solutions are prepared.
Working solution:
Working solution is a name given to a chemical solution made for actual use in the lab, usually made from diluting or combining stock or standard solutions.
Viscosity:
Viscosity quantifies the resistance of a fluid when subjected to deformation from shear stress or tensile stress. In simpler terms, particularly for fluids, viscosity can be described as “thickness” or “internal friction”. For instance, water is considered “thin” due to its lower viscosity, whereas honey is regarded as “thick” because of its higher viscosity. The cgs unit for dynamic viscosity is the poise (P), named in honor of Jean Louis Marie Poiseuille. However, it is more frequently represented, especially in ASTM standards, as centipoise (cP). At a temperature of 20 °C, water exhibits a viscosity of 1.0020 cP. 1 P = 0.1 Pa·s, 1 cP = 1 mPa·s = 0.001 Pa·s.
Freezing Point:
The temperature at which a liquid of specified composition solidifies under a specified pressure.
Flash Point:
The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source. At the flash point, the vapor may cease to burn when the source of ignition is removed.
Hygroscopic:
Hygroscopy refers to a substance’s capacity to draw in and retain water molecules from its environment. This process occurs through either absorption or adsorption, resulting in a physical alteration of the absorbing or adsorbing material, which may manifest as an increase in volume, stickiness, or other physical properties. During this process, water molecules become ‘suspended’ among the molecules of the material.
Accuracy:
The closeness of agreement between the value which is accepted either as a conventional true value or an accepted reference value and the value found.
Precision:
The closeness of agreement (degree of scatter) between a series of measurements obtained from multiple sampling of the same homogeneous sample under the prescribed conditions.