Chemistry of Art 1

Dipole Forces

(Like trying to break the connection between interlocked hands: Medium difficulty) Present in polar molecules Polar Molecules have permanent dipoles the result in the strong attractions between neighboring molecules Permanent dipoles align so that the positive end of one dipole interacts with the negative end of another Consequently, polar molecules have higher boiling points than nonpolar ones even with similar molecular weight Polar molecules rise from the difference in electronegativity Electrons are unevenly shared when atoms of different electronegativities form a bond This results in a partial positive charge on one of the bonding atoms and a partial negative charge on the other In polyatomic molecules, the polar bonds may cancel and result in a nonpolar molecule Polar molecules are not strongly attracted to nonpolar molecules A polar substance will not mix with a nonpolar substance Polar water and nonpolar vegetable oil always separate into two layers

Atomic Number

(Z) represents the numbers of PROTONS in the nucleus of an atom A neutral atom has as many electrons outside its nucleus as protons within its nucleus Opposing charges of protons and electrons hold electrons within a spherical region around the nucleus

Hydrogen Bonding

(like trying to break the connection between linked arms: Most difficult of the three) Polar molecules containing H atoms bonded to either F, O, or N atoms contain an intermolecular force known as hydrogen bond Hydrogen bond is a cohesive attraction between molecules Substances composed of molecules with hydrogen bonding have high boiling points, much higher than expected from their molar mass

Nanometers

(nm) 1 nm = 10-9m

Speed of Light

3.0✖️108m/s

Pigments

A pigment is a material that changes the color of transmitted light as a result of wavelength-selective absorption Colored powders that do not dissolve in a liquid with which they are mixed. They have to be mixed and ground in the liquefied binder Different from dyes that DO dissolve in a liquid Pigments can be natural or synthetic Pigments can be inorganic or organic

Saturated Solution

A solution in which no more solute can be dissolved

Unsaturated Solution

A solution in which the solute concentration is lower than its equilibrium solubility (below saturation point) can still dissolve more solute in solvent

Supersaturated Solution

A solution that contains more of the dissolved solute could be dissolved under normal circumstances (past saturation point) Takes a small incentive to start crystalizing out (form a solid) of solution

Varnish

A thin protective layer between the paint film and the atmosphere Requirements Transparent Colorless Forms a good bond with the dried paint film Removable without affecting the paint in anyway Protects the paint film from dirt and abrasion Cannot be too soft Varnishes can protect from the damaging effects of: Oxygen Moisture You need the varnish to be somewhat elastic so as to Prevent Cracking as the canvas expands and contracts Traditionally, composed of: Drying oil Resin Solvent Can harden in the following ways: Directly after the solvent has evaporated Harden through a curing process after solvent evaporation Curing - chemical reactions between oils and oxygen in the air and reactions between components of the varnish

Ground State

All electrons and in the lowest-energy orbits possible

Ionic Compounds

Also called inorganic compounds Typically made up of metal and non-metal components These components are held together by the attraction of positive and negative charges Metals and nonmetals are a good chemical match Metals lose electrons while Nonmetals gain electrons

Concentration

Amount of solute relative to the amount of solvent Important property of solution

RGB Color Model - Combining Lights

An additive model where red, green, and blue lights (additive primary colors) can be added to produce a wide variety of colors It is primarily used for images in electronic systems

Electron Configuration

Atoms with full outer orbits are extremely stable Atoms with outer orbits that are not full are less stable and undergo chemical reactions attempting to fill the outer orbits

Functionalized Hydrocarbons

Basic hydrocarbon structures from the foundation of a major grouping of organic compounds known Contain additional atoms or groups of atoms called functional groups incorporated into their structure Insertion of functional groups into a hydrocarbon alters its properties All compounds containing the same functional group form a family Have characteristic properties associated with that functional group Representing Functionality Generic symbolism is R-FG, where R is the hydrocarbon part of the molecule and FG is the functional group

Watercolors

Binder: Gum Arabic Made up of polysaccharides (complex sugars) and glycoproteins (amino acids and sugars) Soluble in water Diluent: water Gum arabic needs to be dissolved in water (comes in a powder) Warm water helps the dissolution Heat increases the kinetic energy (energy associated with movement) Helps break apart the solute molecules' (in this case gum arabic) intermolecular forces Increased motion also causes more solvent molecules to contact the solute molecules, pulling on them with more force Result = increased dissolving Note: using boiling water gives an undesired consistency, probably due to undesired chemical reaction Gum arabic slows evaporation in water, allows for a longer time to work on painting (flexibility)

Original Compounds

Came from living organisms and were chemically fragile Easily decomposed with heat Carbon The world contains millions of known compounds, 95% of them have carbon in common Smallest member and only nonmetal of group 4A Forms 4 covalent bonds Forms single, double, and triple bonds Bonds to itself, forming chains , rings, and branched structures Organic Chemistry: Study of carbon - containing compounds and their chemistry

Inorganic Compounds

Came from the Earth and were chemically durable Successfully synthesized by 19th century chemists

Polarity of Hydrocarbons

Carbon and Hydrogen that compose methane have only slightly different electronegativities, making the bonds between them mostly nonpolar Every other hydrocarbon is also nonpolar Hydrocarbons are unable to mix with polar substances such as water Oil and Water DON'T mix Condensed structural formulas are compactly written structural formulas

Electronic transition

Caused by light The energy of this light determines which transition will occur Some molecules absorb many different wavelengths of light Some absorb one, and some absorb none Depends on the electrons and the energy differences between their orbits

Ions

Charged species Results from the removal or addition of electrons Atoms gain electrons to form Anions (Negatively Charged) Atoms lose electrons to form Cations (Positively Charged)

Solution

Defined as a homogeneous mixture of two or more substances (Water and sugar) or (water and salt) are solutions

Radio waves

Discovered by Hertz; wavelengths as long as football fields Used to transmit communication signals

X-Rays

Discovered by Roentgen More energy than UV light

Electron Orbit and Bohr Model

Each orbit is specified with an integer, n, called the orbit's quantum number In the Bohr model, electrons occupy orbits that are at fixed energies and fixed radii Number of Electrons in Shells n = 1, maximum of 2 electrons n = 2, maximum of 8 electrons n = 3, maximum of 8 electrons (Not including transition elements)

Microwave radiation

Efficiently absorbed by water molecules Used in cooking

The Electromagnetic Spectrum

Electromagnetic radiation is the general term for all forms of light Visible spectrum extends from 400 nm to 780 nm

Energy State

Electron configuration of molecule or atom with electrons in particular orbits

Pure Substance

Elements cannot be decomposed into simpler forms by any amount of chemical transformation

Ultraviolet (UV) light

Energetic; can break chemical bonds

Molar Mass

Formula mass of a compound in amu is numerically equivalent to its molar mass in grams per mole (g/mol) Molar mass of an element is the conversion factor between grams and moles of the element Similarly, the molar mass of a compound serves as the conversion factor between grams of the compound and moles of the molecule

Formula Mass

Formula mass of a compound is analogous to the atomic mass of an element It is computed by summing the atomic masses of all the atoms in its formula

Gouache

Gouache paints are made like watercolors Still soluble in water Binder is either gum arabic or dextrin (Made up of several sugar molecules/Soluble in water) Paint film needs to be thicker and more flexible than watercolor Extra glycerine (a three carbon molecule with three alcohol groups) is used in gouache paints so they are more soluble than watercolors Biggest aspect of gouache paints is its opacity (not transparent) easy to cover of mistakes Best paints have a higher proportion of pigment Pigment particles in gouaches are larger With transparent colors, an opaque extender like barium sulfate (insoluble in water) or chalk (cheaper version) are added for more coverage More matte-looking

Important Vertical Columns

Group number based on valence electrons Alkali metals (group 1A) Alkaline Earth Metals (group 2A) Chalcogens (group 6A) Halogens (group 7A) Noble Gases (group 8A)

Light

Has no mass Nothing is known to travel faster than light Light has both wave and particle properties

Infrared (IR)

Heat; used in commercial night vision equipment Used to see chemical bonds

Alkanes

Hydrocarbon. All carbon atoms connected by a single bond One line between one atom and another General molecular formula: CnH2n+2 Ex) if in n level n = 2, there would be 2C and, therefore, 6H making the formula: C2H6 Simplest alkane: Methane, CH4 Carbon forms four single covalent bonds with four hydrogen atoms Straight-chain alkanes are named with the base name, reflecting the number of carbon atoms in the longest continuous chain and using the suffix - ane

Spectroscopy

Identification of unknown substances using their interaction of light with matter. The specific wavelengths of light absorbed or emitted by a molecule of atom are unique to that molecule or atom and can be used to identify it.

Polyatomic Ions

Ionic compound containing anions with more than one atom. Take polyatomic ion as a unit

Concentrated solution

Large amounts of solute mixed with small amounts of solvent

Newton's law of color and light

Light can be separated into the visible spectrum through a prism and it can be combined back into white light

Solvent

Majority component (Does the dissolving) of a solution

Additives

Make it last longer

Electronegativity

Measure of an atom's ability to attract electrons in a covalent bond Electronegativity decreases as one moves down a column and to the left

Colored Lights on Colored Surfaces

Michel-Eugene Chevreul (1786-1889) French Chemist Harmony of dominant colored light - discussed the effect of colored rays of light on colors of material objects (using colors seen through colored glass) Using this theory, colors can be manipulated to create unique art. Colored light can emphasize certain images and mute others

Solute

Minority component (Is dissolved) of a solution

Subtractive Color Model - CYMK

Mixing of pigments and resulting in color is due to what parts of the visible spectrum and NOT absorbed. Mix complementary colors to get black. Cyan-red Magenta-green Yellow-blue

Evaporations

Molecules within a liquid are attracted to their neighbors via intermolecular forces, but thermal energy keeps the molecules moving in a random path At each point in the molecule's path, the molecule is attracted to other neighboring molecules but not strongly enough to hold the molecule in one place At the surface, there are fewer other molecules with which to interact If the molecule were moving particularly fast when it reached the surface, it could overcome the relatively fewer attractions at the surface and shoot off into the air

Gamma (Γ) rays

Most energetic Most do not reach Earth

Naming Ionic Compounds

Names begin with the Cation (metal) Followed by the name of the anion (nonmetal) + ide Ex) NaCl is Sodium Chloride Names for ionic compounds DO NOT contain prefixes to indicate the number of each type of atom Fe2O3 = Iron (III) Oxide

Oil Paintings vs Acrylic Paintings

Oil paintings dry slower - allow for adjustments and blending Acrylic Paintings dry pretty quickly - discourages blending Oil Paint has higher pigment load Linseed oil contains smaller molecules than acrylics, so oil paint can absorb significantly more pigment Need to use "fat over lean" rule for oil to minimize cracking Bottom layers should contain less oil than the top layers since the more oil contained in a layer, the longer it takes to dry It the top layer is dry before the bottom layer does, then the paint cracks You want the upper layer to be flexible (more oil) Since acrylics dry so quickly, cracking is not as much of an issue

Dissolving

One compound disrupts the intermolecular force of the other and then forms intermolecular forces of its own Imagine 2 molecules interact (dispersion, dipole, hydrogen bond) like molecules and another molecule cuts in, breaks the bond between molecules and replaces one with itself For example, water breaks the intermolecular forces between sugar molecules, inserts itself in between the sugar molecules Now, intermolecular forces form between water and the sugar molecule - it dissolves!

Inorganic vs. Organic Pigments

Organic pigments are brighter than Inorganic pigments The particle size of the organic pigments are smaller, which means higher surface area, which means higher color strength. More light can be absorbed per gram of pigment Inorganic pigments are more opaque than Organic pigments Inorganic pigments are generally more fade resistant and chemically resistant that organic pigments Using Organic pigments risks fading Typically Ionic bonds (Inorganic pigments) are shorter than covalent bonds (organic pigment) More energy is needed to break ionic bonds Shorter wavelength of light, risks breaking organic covalent bonds

Pigment Volume Concentration (PVC)

PVC = Pigment volume/(pigment volume + binder volume) x 100% Represents the percentage of pigment in the paint layer after everything is dried

Oil Painting

Paint is opaque. Unable to see what lies behind Binder: Linseed Oil (Most common oil paint binder) A triglyceride (Fat content) Mostly hydrocarbon chain Nonpolar Has dispersion forces To thin Linseed Oil use something Nonpolar Ex: Turpentine Linseed is a drying oil Hardens to a solid film after a period of exposure to the air The double bonds undergo oxidation and the oil polymerizes (forms bonds with another molecule)

Complementary Colors in Art

Pairs of colors (LIGHT), when combined, cancel each other out (look WHITE) Red-Cyan Blue-Yellow Green-Magenta P.S. When combining PIGMENTS, when combined, would cancel each other out and make BLACK The pair of colors create a striking contrast

The Benzene Ring

Particularly stable and is found in many organic molecules When the ring contains substituents, it is called a Phenyl Ring Also called Aromatic Ring because of the notable aroma of many compounds containing such a ring Two or more such rings fused together make polycyclic aromatic hydrocarbons (mothballs)

Four main components of PainT

Pigment Binder Liquid Additives Paint is a Mixture!

Paint

Pigment powder is mixed with a binder The solid particles never dissolve The particles are dispersed and suspended in their resin The mixing is a physical process - there is no chemical change This heterogeneous mixture (suspension) is called a colloid Dilute (liquid) is used to adjust viscosity (how easily the paint flows) Additives - optional for added characteristics (Ex: biocides to fight bacterial growth)

Photodegradation

Properties for Pigments The process of light being able to alter of break chemical bonds of a pigment which results in bleaching

Lightfastness

Properties for Pigments the ability of a material/pigment to resist fading/bleaching when exposed to electromagnetic radiation

Permanence

Properties for Pigments the resistance of a color/color mixture to change when exposed to light and atmosphere

Chemical Properties of Matter

Properties that a substance displays only when changing its composition When matter undergoes a chemical change, it changes its composition The formation of the precipitate seen in class was a chemical change

Physical Properties of Matter

Properties that a substance displays without changing its composition When matter undergoes a physical change, it changes its appearance but NOT its composition The evaporation of alcohol is a physical change, so it melting ice The grinding of the Lake pigment is physical

Tinting Strength

Property of Pigments Ability to conserve its color when mixed with white Determined by: Type of pigment Amount of pigment Fineness of grinding The finer the grind of the pigment, the higher the tinting strength

Granulation

Remember the paints are colloids (suspensions) - coarsely ground pigments could settle on low spots of roughly textured paper Watercolor paper is absorbent. Has grooves, holds water, acts like a paper towel, pulls Chromatography - technique of separation

Frequency

Represented by the Greek letter nu (v) The number of cycles (crests or troughs) that pass through a stationary point in one second Unit is 1/s and is called hertz (Hz) Has an inverse relationship with wavelength v = c/λ Where v is the frequency in units of 1/s, c is the speed of light (3.0✖️108m/s), and λ is the wavelength, usually in meters

Visible Light

Seen by human eyes

Relationship between wavelength, frequency and energy of Light

Shorter wavelengths = greater energy High frequency = High energy Energy needs to break bonds in order for a chemical reaction to occur

Dilute solution

Small amounts of solute mixed with large amounts of solvent The smaller the number for concentration, the more dilute the solution is Less solute = more solvent

The States of Matter

Solid - Incompressible, Fixed Volume, Fixed Shape Liquid - Incompressible, Fixed Volume, Variable Shape Gas - Compressible, Variable Volume, Variable Shape

Excited State

State in which an atom or molecule is said to be in, when an electron has moved to a higher-energy orbit UNSTABLE Energy of the absorbed photon will dissipate in several ways Photodecomposition Electronic relaxation Phosphorescence Fluorescence

Compound

Substance composed of two or more elements combined in a specific ratio and held together by chemical bonds A compound acts and looks very different from its component elements. Salts are compounds Inorganic and organic pigments are compounds

Insoluble dyestuffs

Synthetic Organic Pigments, Don't mix with water

Toners

Synthetic Organic Pigments, Metal salts of organic dyestuffs

Lakes

Synthetic Organic Pigments, Pigments made by precipitating or fixing a soluble dye upon an inert pigment or substance, usually a metallic salt

What does the color of an object depend on?

The color of an object depends on how the molecules or the atom that compose the object interact with the white light. White object reflects all colors. Black object absorbs all colors. Colored object absorbs some colors and reflects others.

Dispersion (London) forces

The weakest intermolecular forces present among all atoms and molecules (like trying to break the connection between fingertips: easy) Result of small fluctuations in the electron cloud or atoms and molecules Small fluctuations result in instances where electrons are not evenly distributed in the molecule or atom IMPORTANT: For chemically similar elements or compounds, the magnitude of dispersion forces is generally proportional to the molar mass of the molecule or atom Two compounds identical in every way other than molar mass. The heavier one will have a larger dispersion force

Binder

To glue pigment particles to one another and to make them stick to the surface being painted

Critical Pigment Volume Concentration

Typically around 30-60% range At or below CPVC: Smoother, glossier, allows more light to be absorbed by the pigment The color is more saturated and deeper Above CPVC: Textured, more matte, scatters more light color appears chalky and more washed out Gets to a point where it is just too much

Alkenes

Unsaturated Hydrocarbons Contain at least one double bond Have fewer hydrogen atoms per carbon atoms than alkanes Flammable (gasoline) and nonpolar like alkanes Double bond makes them susceptible to addition of other atoms Used in many cleaning solvents The name of the alkene is derived from the corresponding alkane by changing the -ane ending to -ene

Alkynes

Unsaturated Hydrocarbons Contain at least one triple bond Have fewer hydrogen atoms per carbon atoms than alkanes Can be derived from alkenes by removing two additional hydrogen atoms from the two carbon atoms on either side of the double bond and placing a triple bond between them The name of the alkyne is derived from the corresponding alkane by changing the -ane ending to -yne Ethyne (acetylene) is used in welding torches

Liquid

Used in thinning paint (different solutions) Solvent used to thin the paint IMPORTANT: once evaporated (Don't want the liquid to stick around) the remaining paint is fixed to the surface So, we want the liquid to have intermolecular forces that can be easily broken in order to evaporate

Egg Tempera

Very old technique, fell out of favor when oil painting became established Binder is egg yolk (mixed with water) Very important to exclude the egg white because the albumen in the egg white will prevent the paint from adhering to the surface being painted Dries very quickly so blending is not possible Egg yolk contains protein and fat When the water from the egg yolk evaporates, it allows for the protein molecule to unravel and crosslink forming a solid film Painting technique needs to be adjusted when using egg tempera Relies on cross-hatching and overlays of glazing to achieve a 3-D image

Acrylic Paint

Very versatile Can be watered down to mimic watercolors Can be applied thickly to mimic oil paints Binder: an Acrylic polymer emulsion (small things coming together) Water is the diluent Polymethacrylate and polyvinylacetate (lower quality) - typical base of binder Lower quality acrylic binders are susceptible to ultraviolet degradation - causes chalking tendencies (pigments powder off) The repetition of the ester groups as you increase this gives enough polarity that acrylic paint is water soluble when wet (because of the oxygens) It forms a waterproof, non-yellowing film when dry Yellowing masks and dulls original colors You can have iridescent acrylic paint where flakes of mica (aluminum silicate) or powdered bronze are mixed with pigment and then prepared with the binder Have a glistening luster in the right light Mistake: DO NOT add more that 30% of water to thin acrylic paint Gives it a wishy washy consistency Unstable Will eventually peel off Molecule are stretched to capacity Next layer will not stick to the first

Wavelength (λ)

Wave properties are embodied in an oscillating wave of electric and magnetic fields Distance between wave crests OR Distance between wave troughs Determines the color of light Determines how much energy one of its photons carries Has an inverse relationship with energy The longer the wavelength, the lower the energy Ephoton∝1/λ Where Ephoton is the energy carried by the photon, λ (Greek letter lambda) is the wavelength of the light, and∝ means "proportional to".

Excited Electrons

When a molecule or atom absorbs light, Electrons are excited from lower-energy orbits to higher-energy ones They required energy (photon) must match the energy required to move an electron from one orbit to the next (cannot stop in between)

Mixtures

combinations of two or more pure substances in variable proportions Classified as homogeneous or heterogeneous Homogeneous: Has the same composition throughout Heterogeneous: Separated into two or more regions with different compositions

Electronic relaxation

electrons return to their original orbitals resulting in an omission of heat or light Excited electron returns to its original orbit This movement produces either heat or light People experience the production of heat due to relaxation when they wear dark-colored shirts on a sunny day

Suspensions and Colloids

heterogeneous mixtures Particles are dispersed but not uniformly Particles do not disappear into the liquid, they suspend themselves in the binder Paint is a colloid, so is milk Particles in a suspension are large enough to settle or be filtered through physical process Colloidal suspensions - particles are small enough to remain suspended in the medium Colloidal particles are large enough to scatter visible light (Tyndall Effect) Light hits particles and goes in different directions Mist and dust particles also disperse light

Phosphorescence

light emitted by a substance without combustion or perceptible heat. occurs in glow-in-the-dark toys (lasts a while)

Capillary Action

liquid filling spaces between solid particles (many times in opposition to gravity) won't work on regular paper Another way to bleed a wash is to have a uniform tone wash and have it meet an area of paper that has been wet with clear water This can actually separate out colors of a pigment

Molarity (M)

moles per liter

Photons

particles of light Considered as tiny packets of energy traveling at the speed of light

Photodecomposition

the breaking down of molecules by radiant energy Process of absorption of a photon with enough energy that can break chemical bonds in molecules Responsible for the dangers of UV light, X-Rays, and gamma rays Reason for fabric colors fading with exposure to sunlight Cells absorb lights, get excited and break apart

Optimum Particle Diameter

the larger size of the inorganic pigments are closer to optimum particle diameter needed to achieve light scattering (about ½ wavelength of the light) Scattering changes the direction of light Light Wavelength = 690 nm (red) → Optimum Particle Diameter =340 nm

Atoms

the smallest identifiable unit of an element

Fluorescence

the visible or invisible radiation emitted by certain substances as a result of incident radiation of a shorter wavelength such as X-rays or ultraviolet light. Black lights emit UV light, which is capable of exciting electrons in a white T-shirt When excited electrons relax, they emit visible light

Converting between Wavelength and Frequency Formula

v = c/λ