Matter, Atoms, Molecules and States of Matter

• Matter possesses mass and occupies space within the Universe
• Atoms constitute matter's fundamental building blocks
• An atom represents the smallest element particle retaining its chemical characteristics
• Atoms consist of protons, neutrons, and electrons
• Protons possess a positive charge, electrons a negative charge, and neutrons no charge
• The element is determined by its number of protons
• The atom's interactions with other atoms rely on its electrons

Molecules

• A molecule forms when two or more atoms join
• Chemical bonds hold together two or more atoms in a molecule
• Molecules may consist of identical or different elements
• A compound describes a molecule with differing atoms
• Substance properties depend on the type and organization of its molecules
• Water (H2O), for instance, consists of two hydrogen atoms and one oxygen atom

States of Matter

• Solid, liquid, gas, and plasma represent the four matter states
• Each state has unique physical attributes
• Matter can shift between these states through temperature and pressure changes
• A solid maintains a defined shape and volume because of its tightly packed, immobile molecules
• A liquid keeps a consistent volume but adapts its shape because its molecules remain close yet mobile
• A gas lacks definite shape or volume due to its widely spaced, freely moving molecules
• Plasma describes a super-heated, electrically charged, ionized gas

Mass

• Mass defines matter's inherent resistance to acceleration
• Mass is the measure of matter within an object
• Greater mass implies greater inertia, which resists changes in motion
• Mass is typically quantified in kilograms (kg) or grams (g)
• As a scalar quantity, mass exhibits magnitude but lacks direction

Weight

• Weight represents the force exerted on an object by gravity
• Weight depends on the object's mass and gravitational field
• Weight is commonly measured in Newtons (N)
• Weight, a vector quantity, possesses both magnitude and direction, pointing downward towards the gravitational center

Mass vs. Weight

• Mass measures an object's matter content, while weight quantifies gravitational force
• Mass remains constant regardless of location, whereas weight changes with gravitational field strength
• An object's mass stays consistent on Earth and the Moon, but its weight differs due to varying gravity levels
• Mass and weight are often used synonymously in everyday language, but they hold distinct scientific meanings

Material Properties

• Material properties dictate behavior under various conditions
• Material properties dictate behavior under various conditions
• Material properties are crucial in engineering for selecting materials for specific uses.
• Physical, chemical, mechanical, thermal, electrical, or magnetic properties are all types of material properties

Physical Properties

• Physical properties can be measured without altering the material's composition
• Examples are density, color, melting point, boiling point, and thermal conductivity
• Density is mass per volume unit
• Color is the visual perception of reflected light
• Melting point is the temperature at which a solid becomes liquid
• Boiling point is the temperature at which a liquid becomes gas
• Thermal conductivity describes the material's ability to conduct heat

Chemical Properties

• Chemical properties relate to a material's reactions with other substances
• Flammability, reactivity, and corrosivity serve as examples
• Flammability defines a material's ability to burn
• Reactivity indicates the ease of chemical reactions
• Corrosivity defines a material's ability to corrode or dissolve

Mechanical Properties

• Mechanical properties reflect a material's response to applied forces or stresses
• Strength, hardness, elasticity, and ductility exemplify mechanical properties
• Strength denotes the capacity to endure stress without fracturing
• Hardness quantifies resistance to indentation or scratching
• Elasticity means the capability to return to its original shape after deformation
• Ductility is the ability to be stretched into a wire

Thermal Properties

• Thermal properties describe how temperature changes affect a material
• Thermal expansion, heat capacity, and thermal conductivity are examples of thermal properties
• Thermal expansion measures size change relative to temperature change
• Heat capacity measures heat needed to increase a material's temperature

Electrical Properties

• Electrical properties define a material's electrical conduction
• Conductivity, resistivity, and dielectric strength are electrical properties
• Conductivity measures electrical conduction ability
• Resistivity measures opposition to electric flow
• Dielectric strength measures the ability to withstand an electric field without breakdown

Magnetic Properties

• Magnetic properties describe how magnetic fields interact with a material
• Ferromagnetism, paramagnetism, and diamagnetism are types of magnetic properties
• Ferromagnetism describes a material strongly drawn to magnetic fields, capable of magnetization
• Paramagnetism defines a material weakly drawn to magnetic fields
• Diamagnetism means that a material is weakly repelled by magnetic fields

Molecular Bonding

• Molecular bonding defines the attractions binding atoms into molecules
• Ionic, covalent, and metallic bonds exist
• The type of bonding determines the substance's properties

Ionic Bonds

• Ionic bonds result from electron transfer between atoms
• This commonly occurs between a metal and a nonmetal
• One atom sheds electrons (becoming a positive cation), while the other gains electrons (becoming a negative anion)
• Electrostatic attraction between these ions forms the ionic bond
• Ionic compounds show high melting/boiling points and water solubility

Covalent Bonds

• Covalent bonds arise from atoms sharing electrons
• This bonding usually involves two nonmetals
• Atoms share electrons for stable electron configurations
• Covalent compounds exist as solids, liquids, or gases, with lower melting/boiling points than ionic compounds

Metallic Bonds

• Metallic bonds come from electron delocalization in metals
• Metal atoms donate valence electrons, creating a sea of mobile electrons
• This electron sea holds metal atoms together
• Electron mobility enables electrical and thermal conductivity in metals
• Metallic bonds give metals properties like malleability and ductility