What law states that the total mass remains constant during a chemical reaction?

The Law of Conservation of Mass states that the total mass remains the same before and after a chemical reaction.

Fill in the blank: In a physical change, ___ new substance is formed.

No

Explain how the Law of Constant Proportions relates to the composition of water.

Water's composition is fixed.

• Elements in fixed ratio.

• 1:8 ratio of H to O.

• Defines water's chemical identity.

True or False: In a closed system, the mass of products can differ from the mass of reactants.

False. In a closed system, the mass of products equals the mass of reactants.

What was a significant contribution of Antoine Lavoisier to chemistry?

Antoine Lavoisier proposed the Law of Conservation of Mass, which asserts that matter cannot be created or destroyed in a chemical reaction.

Riddle: I am formed when two elements share electrons, creating a strong bond. What am I?

A covalent bond.

Fill in the blank: Atoms with less than ___ valence electrons tend to donate electrons.

4

How did Dalton's Atomic Theory explain the constancy of mass in chemical reactions?

Dalton's theory preserves mass in reactions.

• Atoms are indivisible units.

• Atoms rearrange, not created.

• Total mass remains constant.

What type of bond is formed by the transfer of electrons?

An ionic bond is formed by the transfer of electrons between atoms.

True or False: Covalent compounds typically have high melting and boiling points.

False. Covalent compounds usually have lower melting and boiling points compared to ionic compounds.

What is the formula unit mass of sodium chloride (NaCl)?

The formula unit mass of sodium chloride (NaCl) is 58 u, calculated as the sum of the atomic masses of Na (23 u) and Cl (35 u).

Riddle: I can be seen as two atoms combine to form a molecule, what am I?

A chemical bond.

Fill in the blank: When atoms gain or lose electrons, they become ___ and ___ respectively.

Cations; anions

Explain the difference between a molecule and a formula unit.

A molecule differs from a formula unit.

• Molecules are neutral groups.

• Formula units show ion ratios.

• Molecules can exist independently.

What process is illustrated by the reaction of calcium carbonate with hydrochloric acid?

The reaction illustrates a chemical change where new substances are formed, demonstrating the Law of Conservation of Mass.

How do ionic compounds differ from covalent compounds in terms of electrical conductivity?

Ionic compounds conduct electricity in solution.

• Ionic compounds dissociate into ions.

• Covalent compounds lack free ions.

• Conductivity depends on ion mobility.

Fill in the blank: Sodium ions (Na⁺) are formed when sodium ___ an electron.

Loses

How is the molecular mass of water (H₂O) calculated?

The molecular mass of water is calculated as (1 u × 2) + (16 u × 1) = 18 u.

What is the name of the scientist associated with the Law of Definite Proportions?

Joseph Louis Proust is associated with the Law of Definite Proportions.

Riddle: I am the bond that forms when atoms share electrons. What am I?

A covalent bond.

True or False: The mass of products in a chemical reaction can be less than the mass of reactants in an open system.

True. In an open system, gases may escape, causing the apparent mass to decrease.

What is a key characteristic of ionic compounds in terms of their structure?

Ionic compounds form a crystal lattice structure, characterized by a repeating pattern of alternating cations and anions.

Fill in the blank: The process of forming a covalent bond involves ___ of electrons between atoms.

Sharing

How does the arrangement of atoms in a molecule affect its stability?

Atoms arrange to achieve a complete outer shell of electrons, minimizing energy and increasing stability.

What are the two primary types of chemical bonds discussed?

The two primary types of chemical bonds are covalent bonds and ionic bonds.

Riddle: I am a set of atoms bonded together, carrying the properties of a substance. What am I?

A molecule.

Explain the role of energy in the formation of chemical bonds.

Energy is released when bonds form, lowering the total energy of the system and stabilizing the arrangement of atoms.

What happens to the mass of a closed system during a chemical reaction?

The mass remains constant during a chemical reaction in a closed system, as matter is conserved.