thermochem quiz flashcards

What is energy?

The capacity to do work or move matter

What is radiant energy?

Energy from the sun; Earth’s primary energy source

What is thermal energy?

Energy due to random motion of atoms and molecules

What is chemical energy?

Energy stored within chemical bonds

What is nuclear energy?

Energy stored in the nucleus (neutrons and protons)

What is potential energy?

Energy due to an object's position

What is kinetic energy?

Energy of motion: Ek = ½mv²

What is heat?

Thermal energy transferred due to temperature difference

What is temperature?

A measure of thermal energy

What is the difference between temperature and thermal energy?

TEMP ≠ thermal energy; temperature is not the total energy

In what direction does heat flow?

From warmer to cooler objects

What is the formula for work?

w = F × d (force × distance)

What are the units of energy?

SI unit is joule (J); 1 J = 1 kg·m²/s²

What is the calorie (cal)?

Non-SI energy unit; 1 cal = 4.184 J

What is the system in thermochemistry?

The substances under study (e.g., H₂ and O₂)

What are the surroundings in thermochemistry?

Everything outside the system (e.g., cylinder, piston)

What is an exothermic process?

Heat is released from the system to the surroundings (ΔH < 0)

What is an endothermic process?

Heat is absorbed by the system from the surroundings (ΔH > 0)

What is the First Law of Thermodynamics?

Energy is neither created nor destroyed; total energy is constant

What is enthalpy (H)?

The heat content of a system

What is the formula for enthalpy change (ΔH)?

ΔH = H(products) − H(reactants)

What does ΔH represent at constant pressure?

ΔH = q_p (heat at constant pressure)

What is a thermochemical equation?

A chemical equation that includes enthalpy change (ΔH)

What are the rules for thermochemical equations?

Multiply equation → multiply ΔH; Reverse equation → reverse sign of ΔH

What must be included in a thermochemical equation?

Correct physical states and correct ΔH with sign

What is the equation for potential energy?

Ep = mgh (mass × gravity × height)

What is the Law of Conservation of Energy?

Energy changes form but total energy remains constant

What is the formula for calorimetry using specific heat?

q = s × m × ΔT

What is the formula using heat capacity?

q = C × ΔT

What is a coffee-cup calorimeter?

Measures heat at constant pressure (for solution reactions)

What is a bomb calorimeter?

Measures heat at constant volume (for combustion reactions)

What is q in thermochemistry?

Heat transferred during a reaction

When is q positive?

Endothermic process (heat absorbed)

When is q negative?

Exothermic process (heat released)

What is thermal equilibrium?

Heat flows until temperatures equalize

How do you use stoichiometry with ΔH?

Convert grams → moles → use ΔH as a conversion factor

Example: If 10.0 g CH₄ = 0.625 mol and ΔH = -890.3 kJ/mol, what is q?

q = 0.625 mol × (-890.3 kJ/mol) = -556 kJ