Question

part iv - regents questions

1. which process is exothermic?

a) boiling of water
b) melting of copper
c) condensation of ethanol vapor
d) sublimation of iodine

1. the compound carbon dioxide is a gas at 25°c while water is still a liquid. this is because carbon dioxide molecules have a) high intermolecular attraction

b) low intermolecular attraction
c) high kinetic energy
d) low kinetic energy

1. some physical properties of two samples of iodine - 127 at two different temperatures are shown in the table below.

these two samples are two different
a) mixtures
b) substances
c) phases of matter
d) isotopes of iodine

1. a phase change for carbon dioxide that occurs spontaneously at 20°c and 1.0 atmosphere is represented by the balanced equation co₂(s) + energy → co₂(g)

use the key to draw at least five molecules in the box to represent co₂ after this phase change is completed.

1. two samples of gold that have different temperatures are placed in contact with one another. heat will flow spontaneously from a sample of gold at 60°c to a sample of gold that has a temperature of

a) 323k
b) 333k
c) 343k
d) 353k

1. a sample of helium gas is in a sealed, rigid container. what occurs as the temperature of the sample is increased?

a) the mass of the sample decreases.
b) the number of moles of gas increases.
c) the volume of each atom decreases.
d) the frequency of collisions between atoms increases.

1. given the equation: i₂(s) → i₂(g)

which phrase describes this change?
a) endothermic chemical change
b) endothermic physical change
c) exothermic chemical change
d) exothermic physical change

1. which sample of matter sublimes at room temperature and standard pressure?

a) br2(l)
b) cl2(g)
c) co2(s)
d) so2(aq)

1. given the reaction: iron combines with sulphur to produce iron sulphide and heat energy. which statement about this reaction is true?

a) it is an endothermic reaction
b) the average kinetic energy of the product remains constant
c) it is an exothermic reaction
d) the potential energy of the reactants is the same as the potential energy of the product.

1. as a result of dissolving a salt in water, a student found that the temperature of the water increased. from this observation alone, the student should conclude that the dissolving of the salt

a) produced an acid solution
b) was endothermic
c) produced a basic solution
d) was exothermic

1. the average kinetic energy of water molecules decreases when

a) h₂o(l) at 337 k changes to h₂o(l) at 300. k
b) h₂o(l) at 373 k changes to h₂o(g) at 373 k
c) h₂o(s) at 200. k changes to h₂o(s) at 237 k
d) h₂o(s) at 273 k changes to h₂o(l) at 273 k

1. a container of salt water was left open for 2 weeks. after that time only the salt was left in the container. explain why the evaporation that occurred during the investigation is an endothermic process.

Explanation:

1. No clear question. Please clarify.
2. D. was exothermic
3. B. low intermolecular attraction
4. B. chemical, thermal, and electromagnetic
5. C. phases of matter
6. C. an exothermic reaction
7. Sketch five \(CO_2\) molecules spread - out in the box to represent gas phase.
8. A. 323K
9. B. endothermic physical change
10. C. \(CO2(s)\)
11. C. It is an exothermic reaction
12. D. was exothermic
13. A. \(H_2O(l)\) at 337 K changes to \(H_2O(l)\) at 300. K
14. Evaporation requires heat input to change liquid water to water vapor, so it is endothermic.

Answer:

1. No clear question. Please clarify.
2. D. was exothermic
3. B. low intermolecular attraction
4. B. chemical, thermal, and electromagnetic
5. C. phases of matter
6. C. an exothermic reaction
7. Sketch five \(CO_2\) molecules spread - out in the box to represent gas phase.
8. A. 323K
9. B. endothermic physical change
10. C. \(CO2(s)\)
11. C. It is an exothermic reaction
12. D. was exothermic
13. A. \(H_2O(l)\) at 337 K changes to \(H_2O(l)\) at 300. K
14. Evaporation requires heat input to change liquid water to water vapor, so it is endothermic.