Physical Science 8 | Midterm Practice 2

What type of bond involves the complete transfer of electrons from one atom to another?

• ionic bond

• covalent bond

• metallic bond

• hydrogen bond

Answer explanation

An ionic bond involves the complete transfer of electrons from one atom to another, resulting in the formation of charged ions. This is distinct from covalent bonds, where electrons are shared, and other bond types.

What happens to an aluminum atom when it forms a positive ion?

• It gains 3 electrons.

• It gains 3 protons.

• It loses 3 electrons.

• It loses 3 neutrons.

Answer explanation

When an aluminum atom forms a positive ion, it loses 3 electrons. This loss of electrons results in a net positive charge, as the number of protons remains unchanged.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

What are the electrons involved in forming chemical bonds called?

• valence electrons

• core electrons

• bonding electrons

• free electrons

Answer explanation

The electrons involved in forming chemical bonds are called valence electrons. These are the outermost electrons of an atom and play a crucial role in bonding with other atoms.

Tags

NGSS.MS-PS1-1

A group of students conducts an investigation. First, they measure the mass of a seltzer tablet, water, and a plastic bag. Next, they place the seltzer tablet into the bag, add the water, and quickly zip the bag closed. The seltzer and water react, and the bag inflates with gas. Finally, they measure the mass of the three items after the reaction. Which hypothesis does this investigation test?

• The mass of the products is the same as the mass of the reactants.

• Without the plastic bag, there is no conservation of mass in the reaction.

• Vinegar and baking soda combine in a double displacement reaction.

• Atoms lose mass when they react to form a gas.

Answer explanation

This investigation tests the hypothesis that the mass of the products is the same as the mass of the reactants, as the total mass before and after the reaction should remain constant, demonstrating conservation of mass.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following is a characteristic of a homogeneous mixture?

• Components are easily distinguishable

• Uniform composition throughout

• Contains multiple phases

• Substances are visibly separate

Answer explanation

A homogeneous mixture has a uniform composition throughout, meaning its components are evenly distributed and not easily distinguishable. This contrasts with heterogeneous mixtures, where components are visibly separate.

Which of the following can be separated into its components by physical methods?

• Pure substance

• Element

• Solution

• Suspension

Answer explanation

A suspension can be separated into its components by physical methods, such as filtration, because it consists of solid particles dispersed in a liquid. In contrast, pure substances and elements cannot be separated physically.

Which of the following statements is true about a homogeneous mixture?

• It has a non-uniform composition

• Its components are not chemically bonded

• Individual components are easily distinguishable

• It has varying properties in different parts

Answer explanation

A homogeneous mixture has a uniform composition, meaning its components are evenly distributed and not easily distinguishable. However, the components are not chemically bonded, making the statement 'Its components are not chemically bonded' true.

Which of the following statements is true about a heterogeneous mixture?

• It has a uniform composition throughout

• Its components are not chemically bonded

• It cannot be separated into its components

• It has identical properties in all parts

Answer explanation

A heterogeneous mixture consists of different components that are not chemically bonded, allowing them to retain their individual properties. This distinguishes it from homogeneous mixtures, which have a uniform composition.

Which technique is used to separate a solid from a liquid in a heterogeneous mixture?

• Decantation

• Filtration

• Condensation

• Sublimation

Answer explanation

Filtration is the technique used to separate a solid from a liquid in a heterogeneous mixture. It involves passing the mixture through a filter, allowing the liquid to pass while retaining the solid.

What is a characteristic of mixtures?

• Mixtures are composed of only one type of molecule

• Mixtures can be separated into their components by physical means

• Mixtures have a fixed composition

• Mixtures are always in a gaseous state

Answer explanation

Mixtures can be separated into their components by physical means, such as filtration or distillation. This distinguishes them from pure substances, which cannot be separated this way and have a fixed composition.