Chapter 10 Vocabulary Definitions

Chemical Reaction

• Definition: A process that involves the rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction.

Chemical Equation

• Definition: A symbolic representation of a chemical reaction, showing the reactants and products involved, along with their respective quantities and states.
• Example: $2H<em>2 + O</em>2 \rightarrow 2H_2O$

Product

• Definition: The substances that result from the chemical reactions, appearing on the right side of a chemical equation.

Yield

• Definition: The amount of product produced in a chemical reaction, usually expressed as a percentage of the theoretical maximum.
• Equation: $\text{Yield} = \left(\frac{\text{actual yield}}{\text{theoretical yield}}\right) \times 100\%$

Coefficients

• Definition: Numbers placed before the formulas in a chemical equation to indicate the number of units of each substance involved in the reaction.
• Example: In $2H<em>2 + O</em>2 \rightarrow 2H_2O$, the coefficient "2" indicates two molecules of hydrogen and two molecules of water.

Subscripts

• Definition: Small numbers written at the lower right of chemical symbols in a formula to indicate the number of atoms of an element in a molecule.
• Example: In $H_2O$, the subscript "2" indicates there are two hydrogen atoms.

Conservation of Mass

• Definition: A principle stating that mass is neither created nor destroyed in a chemical reaction; the mass of reactants equals the mass of products.
• Importance: This principle is used to balance chemical equations.

Endothermic

• Definition: A type of chemical reaction that absorbs heat from its surroundings, usually resulting in a drop in temperature of the environment.
• Example: Melting ice is an endothermic process as it absorbs heat.

Exothermic

• Definition: A type of chemical reaction that releases heat to its surroundings, typically causing an increase in temperature of the environment.
• Example: Combustion reactions are typically exothermic, such as burning wood.

Activation Energy

• Definition: The minimum amount of energy required for reactants to undergo a chemical reaction; it must be overcome for a reaction to occur.

Surface Area

• Definition: The measure of how much exposed area a substance has; increased surface area allows more particles to collide, which can speed up a reaction.

Catalyst

• Definition: A substance that increases the rate of a chemical reaction without being consumed in the process, often used to lower activation energy.

Inhibitor

• Definition: A substance that decreases the rate of a chemical reaction, often by increasing the activation energy or by blocking the action of a catalyst.