Thermochemistry and Energy Concepts

Thermochemistry is a branch of chemistry that describes the energy changes that occur during chemical reactions.

True (A)

Work is a force acting over a distance, and it is a form of energy that can be expressed as the product of force and distance.

<p>Heat is a form of energy that transfers from a warmer object to a cooler object. (D)</p> Signup and view all the answers

<p>Potential energy is stored energy associated with the position or configuration of an object.</p> Signup and view all the answers

<p>The cat possesses potential energy.</p> Signup and view all the answers

<p>The cat's potential energy is converted into kinetic energy as it falls.</p> Signup and view all the answers

<p>Chemical energy (C), Nuclear energy (D), Electrical energy (E)</p> Signup and view all the answers

<p>Kinetic energy is the energy an object possesses due to its motion.</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>As water flows downward through generators, its kinetic energy is converted into mechanical energy, which in turn drives turbines to produce electricity.</p> Signup and view all the answers

<p>An endothermic reaction is a chemical process that absorbs heat from its surroundings, leading to a decrease in the temperature of the surroundings.</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>The calorie, a non-SI unit of energy, measures the quantity of heat required to raise the temperature of 1 gram of pure water by 1 degree Celsius.</p> Signup and view all the answers

<p>The SI unit of heat and energy is the joule (J).</p> Signup and view all the answers

<p>One calorie (cal) is equivalent to 4.184 joules (J).</p> Signup and view all the answers

<p>The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another.</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>Thermodynamics is the study of energy and its transformations, encompassing heat, work, and the relationships between these concepts.</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>The first law implies that the total amount of energy in the universe is constant, remaining unchanged even as energy transforms between different forms.</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>Humans convert chemical energy stored in food into kinetic energy through metabolic processes that release energy from food molecules, enabling bodily movement and physical activity.</p> Signup and view all the answers

<p>Plants convert light energy from the sun into chemical energy through photosynthesis, a complex process involving chlorophyll and various enzymes, storing the energy in the bonds of glucose molecules.</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>A state function in thermodynamics is a property of a system that depends only on the initial and final states of the system, not on the path taken to reach that state.</p> Signup and view all the answers

<p>Examples of state functions include temperature, pressure, volume, and internal energy.</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>Different paths leading to the same state can require varying amounts of work. The efficiency of the process and the energy required to overcome resistance influence the work involved.</p> Signup and view all the answers

<p>The change in internal energy (ΔE) of a system equals the sum of the heat transferred (q) and the work done (w): ΔE = q + w.</p> Signup and view all the answers

<p>A positive value of q indicates that heat is being transferred from the surroundings into the system.</p> Signup and view all the answers

<p>When a system absorbs heat, its temperature increases as the energy gained from the surroundings is manifested as increased motion of the system's particles.</p> Signup and view all the answers

<p>Heat capacity (C) is a proportionality constant that relates the change in temperature of a system to the amount of heat energy absorbed or released.</p> Signup and view all the answers

<p>The units for heat capacity are typically J/°C or J/K.</p> Signup and view all the answers

<p>Specific heat capacity (Cs) is the amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius (°C).</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>The heat capacity (C) of an object is proportional to its mass (m) and its specific heat capacity (Cs): C = m × Cs.</p> Signup and view all the answers

<p>The amount of heat (q) absorbed or released by an object is calculated using the equation: q = m × Cs × ΔT, where m is the mass, Cs is the specific heat capacity, and ΔT is the change in temperature.</p> Signup and view all the answers

<p>First, adding water increases the mass, meaning the same amount of heat must now warm more matter. Second, water has a higher specific heat capacity compared to steel, requiring more heat energy to raise its temperature.</p> Signup and view all the answers

<p>Enthalpy (H) is a thermodynamic property that accounts for the total heat content of a system, considering both the internal energy and the energy associated with pressure-volume work.</p> Signup and view all the answers

<p>Enthalpy change (ΔH) represents the heat absorbed or released during a chemical reaction at constant pressure. It is commonly referred to as the enthalpy of reaction or heat of reaction.</p> Signup and view all the answers