The accompanying photo shows a pipevine swallowtail caterpillar climbing up a twig. (a) As the caterpillar climbs, its potential energy is increasing. What source of energy has been used to effect this change in potential energy?

The blue curve in the plot here shows the potential energy of an ion A interacting with an ion B as a function of their separation distance. The red curve shows the interaction of ion A with a different ion (ion C) as a function of separation.

a. Do the charges on ions A and B have the same or different signs?

b. Do the charges on ions A and C have the same or different signs?

c. Is the magnitude of the charge on ion B greater than, equal to, or less than the magnitude of the charge on ion C?

a. Does the accompanying energy diagram represent an increase or decrease in the internal energy of the system?

The contents of the closed box in each of the following illustrations represent a system, and the arrows show the changes to the system during some process. The lengths of the arrows represent the relative magnitudes of q and w. (a) Which of these processes is endothermic?

The diagram shows four states of a system, each with different internal energy, E. (a) Which of the states of the system has the greatest internal energy?

The diagram shows four states of a system, each with different internal energy, E. (c) Write an expression for the difference in energy between State C and State D.

Imagine a container placed in a tub of water, as depicted in the accompanying diagram. (a) If the contents of the container are the system and heat is able to flow through the container walls, what qualitative changes will occur in the temperatures of the system and in its surroundings? From the system's perspective, is the process exothermic or endothermic?

In the accompanying cylinder diagram, a chemical process occurs at constant temperature and pressure. (a) Is the sign of w indicated by this change positive or negative?

Consider the two diagrams that follow. (d) Would similar relationships hold for the work involved in each process?

Consider the reaction pictured below in which a molecule of X₂ reacts with a molecule of Y₂ to form two molecules of XY. The reaction is exothermic. Which of the following statements involving the bond enthalpies of X2, Y2, and XY is or are true?

i. 𝐷(X—X),𝐷(Y—Y), and 𝐷(𝑋—𝑌) all have positive values.

ii. 2𝐷(X—Y)<𝐷(X—X)+𝐷(Y—Y).

iii. Δ𝐻=𝐷(X—X)+𝐷(Y—Y)−2𝐷(X—Y).

(b) Why does increasing the temperature cause a solid substance to change in succession from a solid to a liquid to a gas?

(a) What is the electrostatic potential energy (in joules) between two electrons that are separated by 62 pm?

(b) What is the change in potential energy if the distance separating the two electrons is increased to 1.0 nm?

(c) Does the potential energy of the two particles increase or decrease when the distance is increased to 1.0 nm?

(a) The electrostatic force (not energy) of attraction between two oppositely charged objects is given by the equation F = k (Q₁Q₂/d²) where k = 8.99⨉10⁹N-m²/C², Q₁ and Q₂ are the charges of the two objects in Coulombs, and d is the distance separating the two objects in meters. What is the electrostatic force of attraction (in Newtons) between an electron and a proton that are separated by 1⨉10² pm?

A sodium ion, Na+, with a charge of 1.6⨉10^-19 C and a chloride ion, Cl - , with charge of -1.6⨉10^-19 C, are separated by a distance of 0.50 nm. How much work would be required to increase the separation of the two ions to an infinite distance?

A magnesium ion, Mg²⁺, with a charge of 3.2⨉10^-19 C and an oxide ion, O2-, with a charge of -3.2⨉10^-19 C, are separated by a distance of 0.35 nm. How much work would be required to increase the separation of the two ions to an infinite distance?

Predict the chemical formula of the ionic compound formed between the following pairs of elements: (a) Al and F

Classify each of the following as an open, closed, or isolated system:

a. The air in a balloon.

b. The water in a puddle that is evaporating outdoors.

c. A cold beverage in an insulated jug.

d. A chemical reaction in a stoppered flask that produces heat.

(a) According to the first law of thermodynamics, what quantity is conserved?

(c) By what means can the internal energy of a closed system increase?

Calculate ΔE and determine whether the process is endothermic or exothermic for the following cases: (a) q = 0.763 kJ and w = -840 J.

For the following processes, calculate the change in internal energy of the system and determine whether the process is endothermic or exothermic: (a) A balloon is cooled by removing 0.655 kJ of heat. It shrinks on cooling, and the atmosphere does 382 J of work on the balloon.

A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:

Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move. (a) In which case does the gas have the higher temperature after addition of the electrical energy?

A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:

Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move. (b) Identify the sign (positive, negative, or zero) of q and w in each case?

Consider a system consisting of two oppositely charged spheres hanging by strings and separated by a distance r1, as shown in the accompanying illustration. Suppose they are separated to a larger distance r2, by moving them apart. (a) What change, if any, has occurred in the potential energy of the system?

Imagine that you are climbing a mountain. Which of the following are state functions? a. The distance you walk during your climb to the top

Imagine that you are climbing a mountain. Which of the following are state functions? b. The change in elevation during the climb

A system goes from one state to another by two different paths. For Path 1, the system does 140 J of work on the surroundings, and its internal energy increases by 330 J. For Path 2, the system absorbs 220 J of heat from the surroundings.

a. What is the value of q for Path 1?

b. What is the value of w for Path 2?

A system goes from State A to State B by two different paths: Path 1, for which 𝑞₁=38 kJ and 𝑤₁=−97 kJ, and Path 2, for which 𝑞₂=−28 kJ.

a. What is the value of Δ𝐸 for Path 1?

b. What is the value of w for Path 2?