2024 Chemistry Semester Exam

Which process is an example of a chemical change?

• Boiling water

• Combustion of wood

• Crystallization of sugar

• Melting steel

A liquid is cooled during an investigation causing it to solidify. Which of the following most likely occurred?

• Absorption of heat

• A chemical change

• A physical change

• Formation of a new compound

Which of the following observations is usually not evidence of a chemical change?

• Change of shape

• Formation of a precipitate

• Giving off of a gas

• Giving off of heat and/or light

Which phase of matter is the least compressible?

• Gases

• Liquids

• Solids

• Plasma

Water (H₂O) is best described as a(n)

• Atom

• Compound

• Element

• Mixture

After a jar of muddy water is shaken vigorously, the dirt eventually sinks to the bottom. When a flashlight shines into the jar of muddy water, a beam of light reflects off the small particles of soil suspended in the water. How is the muddy water classified?

• A compound

• A homogeneous mixture

• A heterogeneous mixture

• An element

Dmitri Mendeleev was one of the first scientists to arrange the known elements into an organized table. His arrangement, which was by increasing atomic mass, had holes and some elements' chemical and physical behavior did not match with other elements in the same group. Many years later, Henry Moseley arranged the periodic table according to increasing atomic number. What happened to the problems and holes Mendeleev experienced when the elements were arranged by increasing atomic number?

• The problems with chemical and physical behaviors were still present because many of the elements were in the same groups.

• Arranging elements by atomic number fixed the holes and issues with the chemical and physical behavior among elements in the same group.

• The elements in each group were less similar when arranged by increasing atomic number.

• Elements arranged by increasing atomic number show properties that are similar among the periods, not groups.

Why is iodine found after tellurium on the Periodic Table even though its average atomic mass is lower for iodine?

• Elements within a period have similar behaviors

• Elements with a group have different chemical properties

• Elements are arranged by atomic mass not atomic number

• Elements are arranged by atomic number not atomic mass

On Mendeleev's Periodic Table, two spaces were left empty because those elements had not yet been discovered. He predicted that one of the elements would be found to have an atomic mass between that of zinc and arsenic and would behave chemically like silicon. He suggested it be called "ekasilicon". What is the current name of this element?

• Carbon

• Germanium

• Mendelevium

• Selenium

Elements that have been placed in the same group on the Periodic Table share what properties?

• Color and density when in the solid phase

• Electronegativity and atomic radii

• Number of neutrons and radioactive isotopes

• The number of valence electrons and chemical behavior