Chemical Equations and Conservation of Mass

Vocabulary flashcards covering the basics of chemical equations, endothermic and exothermic reactions, open vs. closed systems, and the Law of Conservation of Mass.

Chemical Reaction

A process that occurs when chemical bonds are formed or broken, resulting in a change in chemical composition and producing molecules different from those originally present.

Endothermic Reaction

A reaction that absorbs energy as bonds break, taking in heat from its surroundings and causing the reaction mixture to become cold.

Exothermic Reaction

A reaction that releases energy as bonds form, causing heat to exit and making the reaction mixture hot.

Chemical Equation

A written expression similar to a mathematical equation that depicts the types of reactants and products as well as their relative amounts in a chemical reaction.

Coefficient

A whole number placed directly in front of a chemical formula to show the quantity or number of molecules involved in the reaction.

Subscript

A small number written behind a chemical symbol indicating how many atoms of that specific element are present in a molecule or compound.

Law of Conservation of Matter

A fundamental scientific law stating that matter cannot be created or destroyed in a chemical reaction; the total mass and number of atoms remain identical before and after the reaction.

Antoine Lavoisier

The scientist who first stated in $1788$ that mass remains constant during chemical reactions.

Reactants

The starting substances present before a chemical reaction occurs, written on the left side of a chemical equation.

Products

The substances formed after a chemical reaction takes place, written on the right side of a chemical equation.

Open System

An experimental environment or setup where matter is able to freely enter or escape.

Closed System

A sealed experimental setup (such as a flask with a stopper) where matter cannot enter or escape, allowing mass to be conserved visibly.

Yields Arrow ($\rightarrow$)

The arrow in a chemical equation separating reactants from products, functioning like an equals sign and read as 'yields' or 'produces'.

Aqueous Solution ($(aq)$)

A state symbol indicating that a substance is dissolved in a solution where the solvent is water.

Catalyst

A substance or energy source (such as $H_2SO_4$, $Pt$, or light) represented above or below the reaction arrow that assists a chemical reaction.

Diatomic Elements

Elements that naturally exist in pairs of bonded atoms ($H_2$, $N_2$, $F_2$, $O_2$, $I_2$, $Cl_2$, $Br_2$), remembered by the mnemonic 'Have No Fear Of Ice Clad Brews'.