Question

question 10 (4 points)
(01.05 lc)
which of the following could result from a substance that undergoes a physical change?
a it changes irreversibly.
b it undergoes phase change.
c its elemental composition is altered.
d its atoms rearrange to form a new molecule.

question 11 (4 points)
(01.05 mc)
which of the following best explains what happens when the kinetic energy of particles in a liquid state increases?
a they move slowly enough that the particles are no longer held together, resulting in a gas.
b they move slower, increasing the forces of attraction that hold them together and forming a solid.
c they move fast enough to overcome the forces of attraction that hold them together, becoming a gas.
d they move faster, decreasing the forces of attraction that hold them together and causing particles to ionize and become plasma.

question 12 (4 points)
(01.06 lc)
which of the following is a property of a pure substance?
a it consists of different types of compounds.
b it may have substances in different states of matter.
c it is made up of a single element or type of compound.
d its components can be separated by employing physical methods.

Explanation:

Question 10

• Option a: Physical changes are often reversible (e.g., melting and freezing), so irreversibility is not typical of physical change.
• Option b: Phase changes (like melting, boiling) are physical changes as they involve a change in state without altering the substance's chemical composition.
• Option c: Altering elemental composition means a chemical reaction (new substances form), which is a chemical change, not physical.
• Option d: Atoms rearranging to form new molecules is a chemical reaction (chemical change), not physical.

• Option a: If particles move slowly, they would form a solid (not gas); gas particles move rapidly.
• Option b: Increasing kinetic energy means particles move faster, not slower, so this is incorrect (slower movement leads to solid, but kinetic energy is increasing here).
• Option c: When liquid particles' kinetic energy increases, they move fast enough to overcome intermolecular forces, transitioning to gas (vaporization), which matches.
• Option d: Ionization to form plasma requires extremely high energy (not just increased kinetic energy in a liquid to gas transition), so this is incorrect.

• Option a: A pure substance has a uniform composition; different compounds would make it a mixture.
• Option b: A pure substance has a single state (or can be in one state at a time under given conditions); having different states would imply a mixture (e.g., ice and water together is a pure substance, but the option's wording is misleading—pure substances are defined by single element or compound, not multiple states as a property).
• Option c: By definition, a pure substance is made of a single element (e.g., O₂) or a single compound (e.g., H₂O), so this is correct.
• Option d: Components of mixtures are separated by physical methods; pure substances have no separate components to separate (they are uniform).

Answer:

b. It undergoes phase change.

Question 11