CHEM 121- Chp 5- Thermochemistry

What is the study of heat absorbed during chemical and physical changes?

Thermochemistry

What is the capacity to transfer heat or do work?

Energy

What is energy associated with motion?

Kinetic energy

What is energy associated with position relative to a force?

Potential energy

What is the law of conservation of energy?

Energy cannot be created or destroyed, only transferred or transformed.

What is energy associated with the random motion of particles?

Thermal energy

What does temperature measure?

The average kinetic energy of particles

What is the transfer of thermal energy between objects at different temperatures?

heat (q)

Which direction does heat naturally flow?

From a higher-temperature object to a lower-temperature object.

When does heat flow stop?

When both objects reach the same temperature (thermal equilibrium).

What happens to particles when temperature increases?

Their average kinetic energy increases.

What is a process that releases heat?

Exothermic

What is a process that absorbs heat?

Endothermic

What is the sign of a for an exothermic process?

Negative (q<0) for the system

What is the sign of q for an endothermic process?

Positive (q > 0) for the system.

How can you represent an exothermic reaction?

Reactants → Products + heat.

How can you represent an endothermic reaction?

Reactants + heat → Products.

What happens to the surroundings during an exothermic reaction?

The surroundings absorb heat and warm up.

What happens to the surroundings during an endothermic reaction?

The surroundings provide heat and cool down.

What is an example of an exothermic process?

Combustion (burning fuel).

What is an example of an endothermic process?

Dissolving ammonium nitrate in water in a cold pack.

What is the SI unit of energy?

The joule (J)

What is the energy needed to raise 1 g of water by 1°C?

Calorie (cal)

How many joules equal 1 calorie?

1 cal =4.184 J

What is a food Calorie?

One kilocalorie (kcal) = 1000 small calories

What is the heat needed to raise an object's temperature by 1°C?

Heat capacity (C)

What is the formula for heat capacity?

C = q/ΔT

Is heat capacity extensive or intensive?

Extensive; it depends on the amount of substance.

What is the heat needed to raise 1 g of a substance by 1°C?

Specific heat capacity ( c )

What is the formula for specific heat?

c = q/(mΔT)

Is specific heat extensive or intensive?

Intensive; it depends on the substance, not its amount.

What is the formula for calculating heat?

q = mcΔT

What does q represent in q = mcΔT?

Heat transferred, usually in joules.

What does m represent in q = mcΔT?

Mass in grams

What does c represent in q = mcΔT?

Specific heat in J/(g·°C).

What does ΔT represent?

Temperature change = Tfinal − Tinitial

How do you calculate temperature change?

ΔT = Tfinal − Tinitial

When is q positive?

When the system absorbs heat and its temperature rises.

When is q negative?

When the system releases heat and its temperature falls.

How do you calculate mass using q, c, and ΔT?

m = q/(cΔT)

How do you calculate specific heat using q, m, and ΔT?

q/(mΔT)

How do you calculate heat using heat capacity C?

q = CΔT

What units should be used for q in q = mcΔT?

Joules, if c is in J/(g·°C) and m is in grams.

How do you convert kJ to J?

Multiply by 1,000

How do you convert J to kJ?

Divide by 1,000

How do you identify an unknown substance using specific heat?

Calculate c, then compare it with a reference table.

What is the process of measuring heat transferred during a physical or chemical process?

Calorímetry

What is a device used to measure heat transfer?

Calorimeter

To prevent heat exchange with the outside environment, a calorimeter should be __________.

Insulated

In calorimetry, what is the substance or reaction being studied?

system

In calorimetry, what is everything outside the system that can exchange energy with it?

Surroundings

What occurs when objects reach the same temperature and net heat transfer stops.

Thermal equilibrium

What is the calorimetry equation for two substances?

q₁ + q₂ = 0

What is the relationship between metal and water heat?

qmetal = −qwater

How do you convert solution volume to mass?

Mass = volume × density.

What is the calorimetry equation for a reaction and solution?

qreaction + qsolution = 0

How do you calculate reaction heat from solution heat?

qreaction = -qsolution

If the solution warms up, what happens to qsolution?

qsolution is positive because the solution absorbs heat.

If the solution warms up, what is the sign of qreaction?

Negative; the reaction releases heat.

If the solution cools down, what happens to qsolution?

qsolution is negative because the solution loses heat.

If the solution cools down, what is the sign of qreaction?

Positive; the reaction absorbs heat.

What does a temperature increase during neutralization usually indicate?

The reaction is exothermic.

What does a temperature decrease during dissolution usually indicate?

The process is endothermic.