Exam 4 — In-Depth Study Guide (Conceptual Version)

These flashcards cover essential concepts from the lecture notes on energy, chemical reactions, gas laws, and related theories in chemistry.

What is energy defined as in the context of chemical reactions?

The ability to cause change, move something, heat something, or make a reaction happen.

What is heat?

A type of energy that moves from something hot to something cold.

What units measure energy?

Joule (J) and calorie (cal).

How many Joules are equivalent to one calorie?

1 cal = 4.184 J.

What is kinetic energy?

The energy of motion; the faster something moves, the more kinetic energy it has.

Give an example of kinetic energy.

Boiling water molecules move faster than cold ones.

What is potential energy?

Stored energy due to position or bonds.

Give an example of potential energy.

A stretched rubber band or chemical bonds in gasoline.

What happens during heating and cooling curves?

When a substance is heated, energy may go into state changes instead of increasing temperature.

What do the sloped parts of heating curves represent?

Temperature rises and kinetic energy increases.

What do the flat parts of heating curves signify?

Phase changes where energy breaks or forms bonds without changing temperature.

What happens during melting?

Energy breaks bonds holding solid particles together.

What happens during boiling?

Energy helps liquid particles escape into gas.

What characterizes an endothermic phase change?

It absorbs heat.

What characterizes an exothermic phase change?

It releases heat.

What is bond dissociation energy?

The energy required to break a chemical bond.

How does bond strength relate to dissociation energy?

Stronger bonds have higher dissociation energy.

What is ΔH in terms of chemical reactions?

The total energy absorbed or released in a chemical reaction.

What does a negative ΔH indicate?

An exothermic reaction where heat is released.

What does a positive ΔH indicate?

An endothermic reaction where heat is absorbed.

What are the characteristics of exothermic reactions?

They release heat and products have less energy than reactants.

What are the characteristics of endothermic reactions?

They absorb heat and products have more energy than reactants.

What is required for any reaction to occur?

Particles must collide, have correct orientation, and enough energy (activation energy).

What is activation energy?

The minimum energy required for particles to collide and react.

Name one factor that can help a reaction happen.

Increasing temperature, concentration, or using a catalyst.

What do energy diagrams visualize?

Reactions and the activation energy required for them.

What indicates an exothermic reaction in an energy diagram?

Products are lower than reactants, indicating energy release.

What represents an endothermic reaction in an energy diagram?

Products are higher than reactants, indicating energy absorption.

What is equilibrium in reversible reactions?

A state where forward and reverse reactions happen at the same rate, and concentrations are constant.

What is the equilibrium constant (K)?

K is a ratio of products to reactants, calculated with coefficients.

What does K > 1 indicate?

More products are favored in the reaction.

What does K < 1 indicate?

More reactants are favored in the reaction.

What does K = 1 indicate?

The system is balanced between products and reactants.

How are solids, liquids, and gases differentiated?

By the strength of particle attraction and their kinetic energy.

What are the characteristics of solid particles?

Low energy, strong attraction, vibrate only, fixed shape and volume.

What are the characteristics of liquid particles?

Medium energy, moderate attraction, slide past each other, takes container shape.

What are the characteristics of gas particles?

High energy, weak attraction, move freely, no fixed shape or volume.

What does the Kinetic Molecular Theory of Gases explain?

It describes the behavior of gas particles.

What is gas pressure caused by?

Gas particles colliding with the walls of their container.

What happens when gas volume decreases?

Pressure increases as particles hit the walls more frequently.

What does Boyle's Law state?

Pressure and volume are inversely related at constant temperature.

What does Charles's Law state?

Volume and temperature are directly related at constant pressure.

What must temperature be measured in for gas laws?

Kelvin.

What is Gay-Lussac’s Law?

Pressure increases with temperature at constant volume.

What does the Combined Gas Law express?

It combines pressure, volume, and temperature in one formula.

What does Avogadro’s Law state?

Volume is directly proportional to the number of gas particles at constant temperature and pressure.

What is STP?

Standard Temperature and Pressure; 1 atm and 273 K.

At STP, what is the volume of 1 mole of any gas?

22.4 L.

What is the Ideal Gas Law?

A formula that combines all gas laws: PV = nRT.

What does Dalton’s Law of Partial Pressures state?

Total pressure in a gas mixture is the sum of individual gas pressures.

What can gas stoichiometry connect?

It connects gases to reactions using mole ratios and gas laws.