An element is best defined as a substance that:

A. Can be broken down into simpler substances through chemical means.

B. Cannot be broken down into simpler substances through chemical means.

C. Consists of two or more types of atoms chemically bonded together.

D. Is always a solid at room temperature.

Which of the following statements is true about compounds?

A. They consist of only one type of atom.

B. They are mixtures of different elements.

C. They have a variable composition.

D. They consist of atoms of different elements chemically bonded together.

What is the primary difference between a mixture and a compound?

A. Mixtures have a fixed composition while compounds do not.

B. Mixtures are chemically bonded while compounds are not.

C. Mixtures can be separated by physical methods while compounds cannot.

D. Mixtures are always heterogeneous while compounds are homogeneous.

Which separation technique is most suitable for a mixture of sand and salt?

A. Filtration

B. Distillation

C. Chromatography

D. Crystallization

In the context of separation techniques, what is the primary purpose of recrystallization?

A. To separate mixtures based on different boiling points.

B. To purify a solid by dissolving it in a solvent and then allowing it to crystallize.

C. To separate components of a mixture based on their different sizes.

D. To separate components of a mixture based on their ability to absorb light.

Which of the following is true about intermolecular forces in mixtures?

A. They are stronger in mixtures than in pure substances.

B. They do not influence the formation of mixtures.

C. They play a role in determining the type of mixture formed.

D. They are the same as the forces in chemical bonds.

According to the kinetic molecular theory, what distinguishes a gas from a liquid?

A. The type of particles it contains.

B. The strength of the intermolecular forces between particles.

C. The speed at which its particles move.

D. The temperature at which it exists.

Why are some substances solid and others liquid at room temperature?

A. Due to differences in their molecular weights.

B. Because of differences in the strength of their intermolecular forces.

C. Based on their electrical conductivity.

D. Depending on their color and texture.

During melting, the change of state is:

A. Endothermic, as energy is absorbed to break intermolecular forces.

B. Exothermic, as energy is released by forming intermolecular forces.

C. Isothermic, as no energy change occurs.

D. Adiabatic, as energy is transferred without heat exchange.

Which of the following correctly describes the Kelvin scale?

A. A temperature scale where 0 represents the freezing point of water.

B. A temperature scale based on the average kinetic energy of particles.

C. A scale used exclusively for measuring the temperature of gases.

D. An arbitrary temperature scale unrelated to energy.