The branch of chemistry that studies the heat absorbed or released during chemical reactions and physical changes is called thermochemistry.
Missing Word
thermochemistry
Thermochemistry is the study of the heat and other energy changes that accompany chemical and physical processes. It includes measuring heat flow and calculating enthalpy changes.
Category: Energy Forms and Units
Question 2
The SI unit of energy, equal to 1 kilogram meter squared per second squared, is the joule.
Missing Word
joule
The joule (J) is the SI unit of energy, defined as 1 kilogram meter squared per second squared. It is a small unit, so chemical energy changes are usually reported in kilojoules.
Category: Energy Forms and Units
Question 3
A device used to measure the amount of heat involved in a chemical or physical process is called a calorimeter.
Missing Word
calorimeter
A calorimeter is the apparatus used to measure heat flow. Coffee-cup and bomb designs are two common types used in chemistry courses.
Category: Calorimetry
Question 4
The experimental technique of finding the heat of a process by measuring how much a known mass of water warms or cools is called calorimetry.
Missing Word
calorimetry
Calorimetry is the method of measuring heat transfer by tracking temperature changes in a substance with a known mass and specific heat. The measurement itself is carried out in an instrument built for it.
Category: Calorimetry
Question 5
A process in which the system absorbs heat, so that its ΔH is positive, is described as endothermic.
Missing Word
endothermic
An endothermic process takes in heat, so the system ends with more enthalpy than it started with and ΔH is positive. The opposite kind of process releases heat and has a negative ΔH.
Category: Heat Flow and Sign Conventions
Question 6
The state function represented by H and defined by the equation H = U + PV is called enthalpy.
Missing Word
enthalpy
Enthalpy is the sum of a system's internal energy and the product of its pressure and volume. For a process at constant pressure with only expansion work, the change in enthalpy equals the heat transferred.
Category: First Law and State Functions
Question 7
In chemistry, the matter being studied is the system, and everything outside it that can exchange energy with it is called the surroundings.
Missing Word
surroundings
The surroundings are all matter outside the system that can exchange energy with it. Signs of heat and work are always stated from the point of view of the system.
Category: Heat Flow and Sign Conventions
Question 8
Specific heat is an intensive property, because a small sample and a large sample of the same substance have the same value.
Missing Word
intensive
An intensive property does not depend on the amount of matter present. Specific heat is measured per gram, so a drop of water and a lake share the same value, while the total heat capacity of each differs greatly.
Category: Specific Heat Calculations
Question 9
The property that tells how hot or cold a sample is, and that reflects the average kinetic energy of its particles, is its temperature.
Missing Word
temperature
Temperature measures how hot or cold matter is and is related to the average kinetic energy of its particles. It is distinct from heat, which is energy transferred because of a temperature difference.
Category: Energy Forms and Units
Question 10
Energy transferred when a force moves matter through a distance, as when an expanding gas pushes back a piston, is called work.
Missing Word
work
Work is energy transferred by a force acting through a distance. In chemistry the most common example is pressure-volume work done when a gas expands or is compressed.
Category: First Law and State Functions
Question 11
Mixing hydrochloric acid with sodium hydroxide solution in a foam cup releases heat from an acid-base reaction called neutralization.
Missing Word
neutralization
Neutralization is the reaction of an acid with a base to form water and a salt. It releases heat, so the solution in the calorimeter warms and the heat of reaction can be calculated.
Category: Calorimetry
Question 12
Heat capacity is an extensive property, because a larger object made of the same material needs more heat to warm by 1 °C.
Missing Word
extensive
An extensive property depends on the amount of matter present. Heat capacity grows with the size of the object, while specific heat, measured per gram, does not.
Category: Specific Heat Calculations
Question 13
The standard heat of formation of an element in its most stable form at standard conditions, such as O2 gas, is 0 kJ/mol.
Missing Word
0
By definition the standard enthalpy of formation of an element in its standard state is zero, because forming an element from itself involves no change. These zero values serve as the reference point for every tabulated formation enthalpy.
Category: Hess's Law and Formation
Question 14
The standard state of carbon used as the reference for enthalpies of formation is the form called graphite.
Missing Word
graphite
Graphite is the most stable form of carbon at standard conditions, so it is assigned a standard enthalpy of formation of zero. Diamond, a less stable form, has a small positive formation enthalpy.
Category: Hess's Law and Formation
Question 15
Coffee-cup calorimeters are made from foam cups because foam is a good insulator, which limits heat exchange with the room.
Missing Word
insulator
An insulator is a material that transfers heat poorly. Foam keeps most of the heat of the reaction inside the cup, so the measured temperature change reflects the reaction rather than heat gained from or lost to the room.
Category: Calorimetry