The kinetic energy of a moving object depends on both its mass and its speed.
Correct Answer
True
True. Kinetic energy equals one half the mass times the speed squared, so a heavier object or a faster object carries more kinetic energy. Doubling the speed quadruples the kinetic energy.
Category: Energy Forms and Units
Question 2
A joule is a larger unit of energy than a calorie.
Correct Answer
False
False. One calorie equals 4.184 joules, so the calorie is the larger unit. The joule is the SI unit of energy, and many tables now report values in kilojoules.
Category: Energy Forms and Units
Question 3
When a hot metal block is placed in cool water in an insulated container, the block and the water end at the same final temperature.
Correct Answer
True
True. Heat flows from the block to the water until both reach thermal equilibrium, the point at which their temperatures are equal and net heat flow stops. That shared final temperature is what calorimetry calculations solve for or use.
Category: Calorimetry
Question 4
When two objects at different temperatures touch, heat flows from the colder object to the hotter one.
Correct Answer
False
False. Heat flows spontaneously from the hotter object to the colder one. The transfer continues until the two objects reach the same temperature.
Category: Heat Flow and Sign Conventions
Question 5
For a sample of fixed mass and specific heat, the heat absorbed is directly proportional to its temperature change.
Correct Answer
True
True. In q = m × c × ΔT, holding mass and specific heat constant leaves q proportional to ΔT. Raising the same sample by 20 °C takes twice the heat needed to raise it by 10 °C.
Category: Specific Heat Calculations
Question 6
A substance with a large specific heat warms up quickly when a small amount of heat is added.
Correct Answer
False
False. A large specific heat means each gram needs a lot of heat for each degree of temperature rise, so the substance warms slowly. Water, with its large specific heat, is a familiar example of a substance that resists temperature change.
Category: Specific Heat Calculations
Question 7
A coffee-cup calorimeter open to the air measures heat flow at essentially constant pressure.
Correct Answer
True
True. Because the cup is open to the atmosphere, the pressure stays at atmospheric pressure during the reaction. Heat measured this way corresponds to the enthalpy change of the process.
Category: Calorimetry
Question 8
In a calorimetry experiment with no heat loss, the heat released by the reaction is greater than the heat absorbed by the surroundings.
Correct Answer
False
False. With no heat lost, the heat released by the reaction exactly equals the heat absorbed by the surroundings, so q for the reaction equals the negative of q for the surroundings. This equality is the basis of every calorimetry calculation.
Category: Calorimetry
Question 9
An endothermic reaction carried out in water in a coffee-cup calorimeter causes the temperature of the water to drop.
Correct Answer
True
True. An endothermic reaction absorbs heat, and in a calorimeter that heat comes from the surrounding water, so the water's temperature falls. Dissolving ammonium nitrate in water, as in instant cold packs, behaves this way.
Category: Heat Flow and Sign Conventions
Question 10
Heat absorbed by a system is given a negative sign in the first law equation ΔU = q + w.
Correct Answer
False
False. Heat absorbed by the system is positive, because it adds to the system's internal energy. Heat released by the system is the quantity that carries a negative sign.
Category: First Law and State Functions
Question 11
Combustion reactions, such as the burning of propane in a gas grill, are exothermic.
Correct Answer
True
True. Combustion of a fuel with oxygen releases heat to the surroundings, so its ΔH is negative. That released heat is why fuels are burned for cooking, heating and transportation.
Category: Enthalpy and Thermochemical Equations
Question 12
The standard enthalpy of combustion of a substance is the enthalpy change when 1 gram of it burns under standard conditions.
Correct Answer
False
False. The standard enthalpy of combustion is defined per mole, as the enthalpy change when 1 mole of the substance burns completely under standard conditions. Values are reported in kJ/mol.
Category: Enthalpy and Thermochemical Equations
Question 13
The physical states of reactants and products must be shown in a thermochemical equation because the enthalpy change depends on them.
Correct Answer
True
True. Changing a state changes the enthalpy. For example, forming 1 mole of liquid water from hydrogen and oxygen releases about 286 kJ, while forming water vapor releases about 242 kJ.
Category: Enthalpy and Thermochemical Equations
Question 14
Heating 10 g of water by 5 °C requires the same amount of heat as heating 20 g of water by 5 °C.
Correct Answer
False
False. In q = m × c × ΔT, heat is proportional to mass, so warming 20 g of water by 5 °C takes twice as much heat as warming 10 g by the same amount.
Category: Specific Heat Calculations
Question 15
Under the IUPAC convention, the standard state of a gas corresponds to a pressure of 1 bar.
Correct Answer
True
True. IUPAC defines standard pressure as 1 bar. Many older tables use 1 atm instead, but since 1 bar is about 0.987 atm, the tabulated enthalpy values are essentially the same.
Category: Hess's Law and Formation
Question 16
The standard enthalpy of formation of a compound is the enthalpy change when 1 mole of the compound is decomposed into its elements.
Correct Answer
False
False. The standard enthalpy of formation is the enthalpy change when 1 mole of the compound is formed from its elements in their standard states. Decomposition into elements has an enthalpy change of the same size but opposite sign.
Category: Hess's Law and Formation
Question 17
Bomb calorimeters are used to measure the energy released when foods and fuels are burned.
Correct Answer
True
True. A weighed sample is burned in oxygen inside the sealed vessel, and the temperature rise of the surrounding water reveals how much energy the sample released. This is how the energy content of foods and fuels is determined.
Category: Calorimetry
Question 18
At the same temperature, a 1-liter sample of water and a 100-liter sample of water contain equal amounts of thermal energy.
Correct Answer
False
False. Temperature reflects the average kinetic energy of the particles, but thermal energy is the total for all particles. The 100-liter sample has 100 times as many molecules, so it holds far more thermal energy at the same temperature.
Category: Energy Forms and Units
Question 19
In a chemical reaction, energy can change from one form to another but is neither created nor destroyed.
Correct Answer
True
True. This is the law of conservation of energy. In combustion, for instance, chemical potential energy is converted into heat and light, but the total energy of the system and surroundings stays the same.
Category: First Law and State Functions
Question 20
Specific heat is the heat required to raise the temperature of 1 mole of a substance by 1 °C.
Correct Answer
False
False. Specific heat is the heat required to raise the temperature of 1 gram of a substance by 1 °C. The heat per mole per degree is a different quantity, the molar heat capacity.
Category: Specific Heat Calculations