Chemical Reactions, Systems, and Conservation of Mass

Vocabulary flashcards covering chemical reactions, open and closed thermodynamic systems, reaction types, the Law of Conservation of Mass, chemical versus physical changes, and photosynthesis.

Combustion

A chemical process in which a substance reacts with oxygen to produce heat, such as a hydrocarbon ($CH_4$) reacting with oxygen ($2O_2$) to produce carbon dioxide ($CO_2$), water ($2H_2O$), and heat.

Chemical Reaction

A process in which elements or compounds interact and rearrange to change into new substances.

Reactants

One or more chemical compounds or substances present before a reaction occurs that undergo the chemical change.

Products

New chemical compounds or substances formed as a result of a chemical reaction.

Open System

A system that allows the exchange of both energy (heat energy in/out) and matter (e.g., gas, liquid in/out) with its surroundings or environment.

Closed System

A system that allows only the exchange of energy (heat energy in/out) with its surroundings, while matter is contained and not exchanged.

Chemical Equation Arrow ($\rightarrow$)

A symbol in a chemical equation that shows the direction the reaction is proceeding, pointing from reactants to products.

Synthesis (Combination) Reaction

A type of chemical reaction where two or more substances combine to form a new substance, modeled as $A + B \rightarrow AB$ (for example, $2H_2 + O_2 \rightarrow 2H_2O$).

Decomposition Reaction

A type of chemical reaction where one compound breaks down into two or more substances, modeled as $AB \rightarrow A + B$ (for example, $2H_2O_2 \rightarrow 2H_2O + O_2$).

Single Replacement Reaction

A type of chemical reaction where one element replaces another in a compound, modeled as $A + BC \rightarrow AC + B$ (for example, $Zn + 2HCl \rightarrow ZnCl_2 + H_2$).

Law of Conservation of Mass

A scientific law stating that mass is neither created nor destroyed during a reaction, meaning total mass remains constant ($\text{Mass of Reactants} = \text{Mass of Products}$ or $\text{Mass In} = \text{Mass Out}$).

Chemical Change

A change in which a chemical reaction occurs and forms new products, exemplified by processes such as combustion, rotting, rusting, and digestion.

Physical Change

A change in which matter changes its form but does not change its chemical identity, exemplified by processes such as melting, shredding, boiling, and chopping.

Photosynthesis

A chemical reaction where carbon dioxide, water, and light energy act as reactants to produce sugar and oxygen ($6CO_2 + 6H_2O + \text{Light Energy} \rightarrow C_6H_{12}O_6 + 6O_2$).