Chemistry Lecture: Chemical Changes, Bonding, and Reactions

VOCABULARY flashcards covering phase transitions, signs of chemical reactions, acids/bases/salts, pH indicators, periodic table trends, ionic and covalent bonding, chemical reaction types, and their environmental impacts.

Phase Transitions

Changes of state in matter, categorized into endothermic and exothermic processes.

Endothermic Changes

Phase changes where energy is added, allowing particles to overcome intermolecular forces and move further apart.

Melting

The endothermic process in which a solid turns into a liquid ($Solid \rightarrow Liquid$).

Vaporization/Evaporation

The transition from liquid to gas; vaporization occurs throughout the liquid at a specific temperature, while evaporation occurs only at the surface.

Sublimation

A direct endothermic transition from solid to gas ($Solid \rightarrow Gas$) without becoming a liquid.

Exothermic Changes

Phase changes where energy is removed, causing particles to lose kinetic energy and be pulled closer together.

Freezing

The exothermic transition from liquid to solid ($Liquid \rightarrow Solid$).

Condensation

The exothermic transition from gas to liquid ($Gas \rightarrow Liquid$).

Deposition

A direct exothermic transition from gas to solid ($Gas \rightarrow Solid$) without becoming a liquid.

Chemical Reaction

A process occurring when original substances transform into entirely new ones through an irreversible rearrangement of atoms.

Gas Production

An observable sign of a chemical reaction marked by bubbling, fizzing, or foaming.

Exothermic Reaction

A chemical reaction that releases heat, making the surroundings feel hotter.

Endothermic Reaction

A chemical reaction that absorbs heat, making the surroundings feel colder.

Precipitate

A solid powder or clump that forms and sinks to the bottom when two clear liquids are mixed.

Acids

Chemical substances that release Hydrogen ions ($H^+$) in solution, have a pH less than $7$, and taste sour.

Bases (Alkalis)

Substances that release Hydroxide ions ($OH^-$), accept hydrogen ions ($H^+$), feel slippery, and have a pH greater than $7$.

Salts

Ionic compounds formed through a neutralization reaction between an acid and a base.

pH Indicators

Substances that show visible modifications in color or smell when added to an acid or base due to reactions with $H^+$ or $OH^-$ ions.

Natural Indicators

pH indicators sourced from plants containing pigments sensitive to pH, such as turmeric or red cabbage juice.

Synthetic Indicators

Laboratory-formulated tools for pH testing, including Litmus Paper and Phenolphthalein.

Phenolphthalein

A synthetic indicator that remains colorless in acidic solutions but turns vibrant pink/purple in basic solutions.

Universal Indicator

A pH indicator that displays a full array of colors matched against a chart to reveal exact pH levels.

Olfactory Indicators

Substances that alter or lose their characteristic smell in acidic or basic environments, such as onion or clove oil.

Periods

The seven horizontal rows across the periodic table.

Groups

The vertical columns in the periodic table of elements.

Ionic Bonding

A bond formed by the complete transfer of electrons from a metal to a non-metal, held together by electrostatic attraction.

Covalent Bonding

A bond formed strictly between non-metals when atoms share electrons to achieve stability.

Diatomic Elements

Seven elements ($H_2$, $N_2$, $F_2$, $O_2$, $I_2$, $Cl_2$, $Br_2$) that naturally exist as pairs when pure gases.

Synthesis Reaction (Combination)

A reaction where two or more simple substances combine to form one complex structure ($A + B \rightarrow AB$).

Decomposition Reaction

A reaction where a single compound breaks down into two or more simpler substances ($AB \rightarrow A + B$).

Single Displacement Reaction

A reaction where a more reactive element replaces a less reactive element in a compound ($A + BC \rightarrow AC + B$).

Double Displacement Reaction

A reaction where two compounds exchange ions to form two new compounds ($AB + CD \rightarrow AD + CB$).

Combustion Reaction

A rapid reaction with oxygen producing heat, light, carbon dioxide ($CO_2$), and water vapor ($H_2O$).

Acid-Base Reaction

A reaction between an acid and a base that produces salt and water ($Acid + Base \rightarrow Salt + H_2O$).

Photosynthesis

A synthesis reaction where plants use light energy to convert carbon dioxide ($CO_2$) and water into glucose and oxygen ($O_2$).

Ocean Acidification

The process where oceans absorb excess atmospheric $CO_2$, making water more acidic and dissolving marine shells made of calcium carbonate ($CaCO_3$).

Leachate

A toxic liquid produced by decomposition in landfills that can contaminate groundwater.