Chemistry's Role in Engineering Disciplines

The Role of Chemistry in Engineering

• Engineering uses science by designing structures, machines, apparatus, or processes.
• Engineering needs material properties knowledge and science and math understanding.
• Engineers balance science with economics, safety, efficiency, reliability, and constructability.
• A material best in design might not be economically practical.
• The Accreditation Board for Engineering and Technology (ABET) lists 28 engineering areas.
• Chemical, Biochemical, and Bio-molecular Engineering use chemistry daily.
• Systems Engineering is not directly involved with chemical principles.
• Disciplines need chemistry, materials science, or environmental expertise to solve problems.
• Engineering indirectly involves chemical principles because they determine materials' properties, electrical systems, electronic devices, energy production, and environmental effects.
• Engineers use macroscopic material properties like hardness, strength, malleability, or conductivity.
• Chemistry studies matter properties and behavior on microscopic and atomic/molecular scales.
• Matter description on a small scale supports reasons for macroscopic behavior.
• Atomic/molecular forces explain material qualities and reactions to external stresses.

Scratch Hardness Case Study

• Scratch hardness measures a material's resistance to being scratched or abraded.
• Hardness is key for mechanical tools where friction matters.
• The Mohs scale, made in 1812 by German geologist Friedrick Mohs, is a measure of hardness
• The Mohs scale ranged from diamond (10 - hardest) to talc (1 - softest).
• Other minerals got intermediate values based on scratch ability.
• Diamond and graphite, made of carbon, differ in Mohs hardness by nearly 10 points.
• Mohs scale is relative, not linear.
• Absolute hardness uses a sclerometer to measure scratch width from a moving diamond stylus under a constant, calculated as applied force divided by scratch width times a geometrical device constant.
• Different carbon forms' scratch hardness is due to different structure and bonding at the microscopic level.
• Diamonds have hardness, and are used in high precision auto parts.
• Graphite is soft, used in pencils, and is a good lubricant.
• Carbon nanotubes possess excellent mechanical characteristics, chemical stability, along with high electrical and thermal conductivities.
• Nano-crystalline diamond has a Mohs scale scratch hardness greater than 10.
• A material property that limits usability is its ability to react, like metal corrosion in the air due to oxygen reactions, which Chapter 10 explains.
• Chemical principles cause corrosion.
• Knowing these helps anticipate corrosion probability and choose materials in different conditions.

Green Engineering

• Scientists and engineers are aware of Earth's resource limits and stress from population and technology.
• Rapid tech progress disregarding health/environmental impacts brings future disaster.
• This led to "Green Chemistry" and "Green Engineering" projects.
• Green Chemistry reduces hazardous substance use/creation, while Green Engineering has a broader focus.
• Green Engineering designs, develops, and uses cost-effective products, processes, and systems while reducing health/environmental risk.
• It focuses on minimizing effects on the planet's sustainability using green science and tech
• Goals exceed product/process impacts, including material/energy lifecycle design that starts from raw material acquisition, like mining, drilling, or harvesting.
• Life cycle assessments continue through use, distribution, disposal, or recycle.
• Green Engineering wants processes, materials, energy, final products to be nonhazardous, lowering energy/material use, and stopping waste.
• Materials/energy should be renewable, and products/systems must be designed for disposal or recycle.
• The American Chemical Society & EPA have outlined Green Engineering.
• The major points are: Use nonhazardous materials and energy; prevent waste; minimize energy/material use; use renewable resources; reduce material types; use local materials; design for recycle; maximize efficiency and durability without environmental immortality; choose simplicity; meet needs while minimizing excess.
• Green Engineering prevents negative environmental impacts at design start rather than cleanup later and there is no totally zero-impact energy/resource.
• Mitigation and adaptation to climate change coupled with clean energy rank as top millennium "Grand Challenges for Engineering”, which require carbon capture and sequestration.
• Emissions of greenhouse gases need to be reduced in addition to infrastructure for severe weather, and require efficient, economical, safe carbon-free energy processes by engineers and chemists.

The Physical States of Matter

• Matter is anything with mass (m) and volume (V).
• Matter is general by chemists/physicists, while "material" is more specific to engineers.
• Density is mass/volume (m/V), symbolized by Greek letter ρ.
• SI density units are kilograms/cubic meter (kg/m3) or grams/cubic centimeter (g/cm3).
• Density is also measured as grams/milliliter (g/mL) in non-SI units.
• 1 mL equals 1 cm3 since a liter equals 0.001 m3.
• Density varies with temperature and pressure.
• Compressible material density rises with pressure since volume reduces while mass stays constant.
• Material volume increases with temperature, reducing its density, and may drop rapidly, meaning a change in phase or state.
• Water density rises from below 0°C to 100°C, implying a volume decrease, and can only be explained with a thorough under- standing of the forces and properties that control the behavior of water on a molecular level. Water's anomalous behavior comes from properties setting it apart from other materials
• Observable matter properties include physical state, of which there are 5: superfluids, solids, liquids, gases, and plasmas.
• Daily observable matter includes solid, liquid, gas, and plasma increasing temperature and decreasing densities, while a fifth state relevant to engineers is superfluidity, only at low temps.
• Classical matter states include solid, liquid, and gas that differ in properties as temperature rises.
• Solids have a fixed shape/volume, are non-compressible, and maintain constant density, changing shape only with applied force.
• Liquids have fixed volume, variable shape, flow, and take shape of the container with one free surface, with limited compression and density change.
• Gases lack fixed shape/volume, expand to fill containers, are highly compressible, and strongly change with pressure/temp.
• Plasmas and super-fluids are more extreme states of matter.
• Plasmas exist at high temperature, formed by superheating gas, similar to gases, but being highly conductive and are in display screens, lighting, and welding.
• Super-fluids are at low temperatures, formed from rapidly cooling gas, liquid, or solid.
• Super-fluids, like liquid helium, exhibit frictionless flow, have high thermal conductivity and are effective in superconductors.
• Fluids (liquids, gases, plasmas, and super-fluids) flow under shear stress.
• Democritus, a Greek philosopher, suggested matter comprises atomos, meaning "not to be cut.” These microscopic particles explain macroscopic properties, and make the material.
• Views on matter's nature point all matter is made of tiny indivisible particles and pure things have their own particle and there are large spaces between the particles.
• The particles are in constant motion, and particles that are higher in temperature move faster than ones with lower temperature.
• These views explain classical states of matter, shown as solids being fixed in positions with minimal space and movement, which explains their fixed, rigid shapes.
• Liquids have more space and motion, and move freely, while gases have wider spread, rapid movement, and greater spaces. Therefore, gases quickly grow to take up the container's volume; Gases are more easily compressed because of there large space.
• Increasing gas temperature increases particle motion, causing energetic collisions and charged particles that make plasmas conductive.
• Conversely, rapidly lowering temperature slows particles.
• At very low temperatures, individual particle stops and moves, acting in sync as a single one
• Super-fluids have zero resistance to its motion, causing them to defy gravity and surface tension.
• Super-fluid liquid helium climbs a container wall as a film and falls to the liquid below, showing zero resistance to motion.

Classification of Matter

• Democritus introduced his particulate theory in 400 BC, but John Dalton is credited with creating the modern atomic theory of the 1800's.
• Democritus' theory was philosophical whereas Dalton's was based on observations and measurements.
• Dalton's theory states all matter consists of atoms that cannot be subdivided, created, or destroyed and atoms of the same items are the same in size, weight, and properties.
• Different elements' atoms can combine in whole number ratios to make chemical compounds and atoms combine, separate, or rearrange in chemical reactions.
• Dalton added the concept of elements having specific weights and atoms combining in whole number ratios for chemical reactions
• Joseph Proust's "definite proportions" states compounds always hold the same element proportions by mass.
• Compound mass equals component masses, smallest molecules have tightly bonded elements.

Separation of Mixtures

• Most elements or compounds occur naturally in mixtures, while laboratory/industrial processes make impure compounds.
• Mixtures should be separated into pure components for utilization.
• Separation is vital in industrial processes from energy to building materials.
• Some processes need total separation, others need partial, where the pure materials keeps its identities, and differences separate the mixture.
• Separation methods are based on differing pure element properties; harsher conditions can alter pure elements.
• Mixture separations can be based on physical or chemical properties that include sedimentation, filtration, distillation, fractional distillation, sublimation and effusion.