Introduction to Matter and Chemistry

Learning Objectives

• Substances consist of smaller particles.
• Pure substances and mixtures are different.
• Elements and compounds are different.
• Homogenous and heterogenous mixtures can be distinguished.
• Physical and chemical properties can be distinguished, and examples can be given.
• Extensive and intensive properties can be distinguished, and examples can be given.

Definition of Matter

• Matter is anything with mass that occupies space.

Chemistry Defined

• Chemistry studies matter, its composition, structure, and properties.
• Chemistry also examines the processes matter undergoes.
• The field studies energy changes related to these processes.
• Chemistry is also a branch of physical science and studies change.

Matter - Basic Units

• Atom: Smallest amount of matter.
• Element: Contains atoms with the same number of protons and atomic number; different types are called elements.
• Elements cannot be broken down by non-nuclear chemical reactions.
• Molecule: Formed when atoms combine.
• Consists of two or more atoms held by chemical force.
• Compound: A molecule containing at least two different elements.
• Particle: A minute portion of matter.
• Composite Particle: Subatomic particle composed of smaller elementary particles like quarks. Ex. Quarks
• Elementary Particles: Protons, neutrons, and electrons are examples of elementary particles.

Phases of Matter

• Matter exists in solid, liquid, and gas phases.

Solid Phase

• Definite shape and volume.
• Does not conform to the container shape.
• Particles are tightly packed and organized.
• Rigidity or hardness is not the determining factor.

Liquid Phase

• Varying shape but definite volume.
• Conforms to the container shape.
• Particles are close together but less tightly packed than solids, not rigidly placed.

Gas Phase

• Varying shape that conforms to the container's shape.
• Does not have a definite shape or volume.
• Particles are placed apart and disorganized.

True or False statements on phases of matter

• Solids have a definite shape and volume.
• Liquids have an indefinite shape but a definite volume.
• Gases have an indefinite shape and volume.

Pure Substance

• Pure substances possess definite and constant composition along with distinct chemical properties.
• It always has the exact same chemical and physical properties under the same conditions.
• Water is always 11.2% Hydrogen and 88.8% Oxygen by mass.

Element

• Elements contain only one type of atom.
• That atom has definite and unique properties.
• A pure substances can only be made by that atom
• Pure copper wire is an example.

Compounds

• Compounds consist of two or more elements joined by chemical force.
• They have definite and constant composition.
• Water is 11.2% hydrogen and 88.8% oxygen by mass and that it has the same chemical and physical properties under the same conditions.
• Water, although composed of hydrogen, has different properties from its elements.

Molecules

• Molecules are formed when two or more atoms are held together by chemical force.
• There is no such thing as a molecule of an ionic compound.

Mixtures

• Mixtures are two or more pure substances physically combined in variable proportions.
• Each substance in a mixture retains its own set of chemical and physical properties.

Homogeneous Mixture

• Homogeneous mixtures have the same proportions of components throughout.
• Components are evenly mixed
• It has one phase, with components not visually distinguishable.
• Components retain their own chemical and physical properties.

Solution

• Solutions are homogeneous mixtures with a consistent solvent-to-solute ratio.
• They have one phase where the solute is not easily differentiated from the solvent.
• Solutions are stable and do not settle over time.
• The components of a solution each have different properties.
• They do not scatter a beam of light (no Tyndall effect).

Examples of Solutions

• Type of solution: Gas in Gas, Example: Air, Solvent: Nitrogen, Solute: Oxygen
• Type of solution: Gas in Liquid, Example: Carbonated water, Solvent: Water, Solute: Carbon dioxide
• Type of solution: Liquid in Liquid, Example: Antifreeze, Solvent: Water, Solute: Ethylene glycol
• Type of solution: Liquid in Liquid, Example: Vinegar, Solvent: Water, Solute: Acetic acid
• Type of solution: Liquid in Solid, Example: Dental Amalgam, Solvent: Silver, Solute: Mercury
• Type of solution: Solid in Solid, Example: Steel, Solvent: Iron, Solute: Carbon

Heterogeneous Mixture

• Heterogeneous mixtures have a non-uniform composition where component distribution varies.
• The distribution of components are uneven.
• They have two or more phases

Suspension Mixture

• Suspensions are heterogeneous mixtures.
• They contains solid particles large enough to settle at the bottom.
• Solute particles do not dissolve but are suspended throughout the medium.
• Light scattering is variable.

Colloid Mixture

• Consist of mixed substances
• A phase is dispersed throughout another.
• The dispersed phase size falls between solutions and suspensions.
• It exhibits the Tyndall effect by scattering light.

Types of Colloid

• Solid sol: Solid particles in solid medium
• Example: Colored gems
• Sol: Solid particles in liquid medium
  • Example: Blood
• Solid emulsion: Liquid particles in liquid medium
  • Example: Butter
• Emulsion: Liquid particles in liquid medium
  • Example: Milk
• Solid foam: Gas particles in solid medium
  • Example: Marshmallow
• Foam: Gas particles in liquid medium
  • Example: Whipped cream
• Aerosol: Solid particles in gas medium
  • Example: Smoke
• Aerosol: Liquid particles in gas medium
  • Example: Clouds

Properties of Matter

• Properties of matter serve as a basis for identification and differentiation.
• Divided into physical and chemical properties.

Physical properties

• Physical properties can be observed or measured without changing the identity and composition.
• Physical properties include color, odor, shape, melting point, boiling point, density, hardness, volume, mass, and length.

Extensive Properties

• Physical properties that depend on the amount of mass or matter present.
• Volume, length, shape and mass are examples.

Intensive Properties

• Physical properties that do not depend on the amount of matter present.
• Color is the quality of an object as reflected with transmitted light.
• Malleability is a substances ability to be beaten into thin sheets.
• Ductility is a substances ability to be drawn into thin wires.
• Conductivity is a substances ability to allow the flow of energy or electricity.
• Hardness is how easily a substance can be scratched.
• The temperature at which the solid and liquid phases are in equilibrium at atmospheric pressure is the Melting/Freezing Point.
• Boiling Point is the temperature at which the vapor pressure of a liquid is equal to the pressure on the liquid.

Density - Intensive Property

• Density is the amount of matter in a given volume, independent of substance quantity.
• Density = Mass / Volume
• Unit is measured in g/cm³

Chemical Properties

• Chemical properties can only be observed when the substance's identity changes.
• These are involved in transforming substances into materials with different structures and compositions.
• Reactivity is the ability of matter to combine chemically with other substances. – Potassium, very reactive with water, forms potassium hydroxide solution and hydrogen gas.
• Toxicity is the degree to which a substance can harm an organism.
• Lead is toxic which damages various parts of the human body including bones, the heart, kidneys, intestines, etc.
• Flammability is a compound's ability to burn when exposed to a flame.
• Oxygen causes wood to carbonize when it burns.

Physical Change

• Physical changes do not alter the substance's identity.
• It affects physical properties like shape, phase, size, or state
• You may or may not be able to undo this change.

Phase Transition

• Is a physical change.
• A substance undergoes changes without its chemical composition changing.

Types of Phase Change

• Evaporation: Conversion of liquid to gas, useful in sorting mixtures like salt solutions.
• Sublimation: Conversion of solid to gas without passing through the liquid state like napthalene.

Physical Changes Examples

• Freezing water for ice cubes.
• Sanding a piece of wood.
• Cutting hair.
• Crushing an aluminum can.
• Bending a paper clip.
• Mixing oil and vinegar.

Chemical Changes

• Chemical changes alter the identity of a substance.
• A chemical reaction is where something changes into an entirely different substance.
• Iron rusting and forming iron oxide is a chemical change.

Deciding Whether Processes Are Primarily a Physical or a Chemical Change

• Frost forming on a cold winter night: Physical
• A match igniting to form ash and a mixture of gases: Chemical
• Perspiration evaporating after jogging: Physical
• A silver fork tarnishing slowly in air: Chemical
• Gasoline fumes igniting in an engine's cylinder: Chemical
• Freezing water: Physical
• Sanding a piece of paper: Physical
• Cutting your hair: Physical
• Crushing an aluminum can: Physical
• Bending a paper clip: Physical
• Mixing oil and vinegar: Physical
• Soured milk: Chemical
• Breaking a piece of chalk in two: Physical
• Melting of ice: Physical
• Hot gas produced when oxygen and hydrogen mix to make water: Chemical
• Sugar dissolving in water: Physical
• Butter melting: Physical
• Copper reacts with carbon dioxide to form copper carbonate: Chemical
• Effervescent tablets bubble when the citric acid and baking soda react with water: Chemical
• Melted butter hardening: Physical
• Mixing an acid and a base: Chemical
• Digesting sugar with the amylase in saliva: Chemical
• A lump of clay into a figure: Physical
• Mixing baking soda and vinegar to produce carbon dioxide gas: Chemical

Key Points to Remember

• A physical change caused by heating may be reversed by cooling.
• Heating causes a chemical change can only be reversed only by other chemical changes.