Chemistry (Unit 2 Quiz 2)

Matter Classification, Chemical and Physical Changes, Chemical and Physical Properties, States of Matter, Phase Changes, Heating Curve

Atom

The basic building blocks of matter

Element

Cannot be broken down through chemical reactions (ex. Ne, Cu, Pb, Sn)

Monoatomic: Single atom

Diatomic: 7 elements exist in nature as 2 atoms chemically bonded together (H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂)

Molecule

Pure substance with atoms of 2 or more same or different nonmetal elements chemically combined

Compounds

Pure substance made of 2 or more elements chemically combined (ex. H₂O, FeS₂)

Properties change when you chemically combine elements

Homogeneous Mixtures

Mixtures that contain pure substances that appear uniform and evenly mixed (ex. air, brass, steel, bronze)

Also known as Solution

Heterogeneous Mixtures

Mixture combining pure substances having non-uniform distribution or unevenly mixed

Parts of the mixture can be easily seen and separated

Also known as colloids or suspension

• Suspension: you have to stir something to be evenly mixed

Chemistry

The study of the composition, structure, transformation of matter

Physical change

• No change in chemical composition

• Same substance

• Tend to be reversible

ex. blending, mixing, bending, sculpting, shredding, tearing boiling, evaporating, melting, sublimation, deposition

Solid

• Not easily compressed → particles have limited free space

• Rigid structure → does not flow easily

• Fixed shape and volume

• Tightly packed together

• Vibrating in a fixed position

• Least kinetic energy

Liquid

• Not easily compressed → particles have limited free space

• Flows easily → particles can move past one another

• Assumes shape of the part of the container it occupies

• Fixed volume, no define shape

Gas

• Compressible → lots of free space between particles

• Flows easily → moving rapidly and freely

• Assumes the shape and volume of the container

• Most kinetic energy

Close Circuit

Matter can not move freely

Energy can move freely

Isolated Circuit

Matter can not move freely

Energy can not move freely

Open Circuit

Matter can move freely

Energy can move freely

Endothermic

Requires energy (heat)

Heat is being added

Object will feel hotter than surrounding environment

Exothermic

Heat is being removed/released

Object will feel colder than surrounding environment

Heating/Cooling Curve

Shows what is happening to the Kinetic Energy of molecules

• As temperature increases, kinetic energy increases

• As temperature decreases, kinetic energy decreases

Energy added during a phase change is being used to overcome intermolecular forces of attraction

Chemical change

• Chemical composition changes

• New substance is formed

• Tend to be “one-way” (irreversible)

ex. 2H₂ + O₂ → 2H₂O₂

Burning, cooking, rusting, corrosion, oxidation, tarnishing, decomposition, spoiling, rotting, decaying

Indicators of chemical change/reaction

• Energy change → loss/gain of heat

• Light produced

• New gas (bubbles form)

• Solid precipitate is produced

• New substance is formed

• Color change

Exothermic changes/reactions

Releases energy (can be in the form of heat or light)

ex. fireworks, glow sticks, fireflies

Endothermic changes/reactions

Environment or surrounding feels colder

Take in heat for reaction

ex. photosynthesis

Extensive physical property

Depends on the amount of substance (will change depending on the amount of the substance)

ex. mass, volume, shape, length

Intensive physical property

Will not change depending on the amount of the substance

ex. color, boiling point, melting point, density, conductivity, specific heat, malleability, ductility, luster, opacity, viscosity, attraction to magnets

Melting/Fusion

Phase change from solid to liquid

Gains kinetic energy

Vaporization/Evaporation

Phase change from liquid to gas

Gains kinetic energy

Condensation

Phase change from gas to liquid

Loses kinetic energy

Freezing

Phase change from liquid to solid

Loses kinetic energy

Sublimation

Phase change from solid to gas

Gains kinetic energy

Deposition

Phase change from gas to solid

Loses kinetic energy

STP

Standard Temperature and Pressure