Unit 4 Test EOY Review

Which of the following is NOT a physical property of matter?

• Color

• Density

• Flammability

• Melting point

Answer explanation

Flammability is not a physical property; it is a chemical property that describes how a substance reacts with fire. In contrast, color, density, and melting point are all physical properties that can be observed without changing the substance.

When salt dissolves in water, what type of mixture is formed?

• Heterogeneous mixture

• Homogeneous mixture

• Suspension

• Colloid

Answer explanation

When salt dissolves in water, it forms a homogeneous mixture because the salt ions are evenly distributed throughout the water, creating a uniform solution. This contrasts with heterogeneous mixtures, where components remain distinct.

Which statement about the periodic table is FALSE?

• A. Elements in the same group have similar chemical properties.

• B. Elements are arranged in order of increasing atomic number.

• C. All elements in period 3 have the same number of valence electrons.

• D. Metals are located on the left side of the periodic table.

Answer explanation

Choice C is false because elements in period 3 have varying numbers of valence electrons: sodium has 1, magnesium has 2, and aluminum has 3, while others have more. The other statements about groups, atomic number, and metals are true.

During a chemical reaction, what is conserved?

• The number of molecules

• The chemical properties

Answer explanation

During a chemical reaction, the number of molecules is conserved, meaning that the total count of reactant and product molecules remains the same. This is a fundamental principle of the conservation of mass.

Tags

NGSS.MS-PS1-5

Which part of the atom contains protons and neutrons?

• A

• B

• C

• Both A and B

Answer explanation

The protons and neutrons are located in the nucleus of the atom, which corresponds to choice A. Choice B does not contain these particles, making A the correct answer.

Tags

NGSS.MS-PS1-1

If a substance has a pH of 2, which of the following statements is true?

• It is a strong base.

• It is a strong acid.

• It is a weak base.

• It is neutral.

Answer explanation

A pH of 2 indicates a high concentration of hydrogen ions, characteristic of strong acids. Therefore, the correct statement is that it is a strong acid.

Which of these is a chemical change?

• Ice melting

• Salt dissolving in water

• Wood burning

• Sugar being ground into powder

Answer explanation

Wood burning is a chemical change because it transforms the wood into ash and gases through combustion, altering its chemical structure. In contrast, melting ice, dissolving salt, and grinding sugar are physical changes.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

What is the primary difference between an element and a compound?

• Elements can be broken down by physical means, compounds cannot.

• Compounds can be broken down by chemical means, elements cannot.

• Elements are always gases, compounds are always solids.

• Compounds are naturally occurring, elements are synthetic.

Answer explanation

The primary difference is that compounds can be broken down into simpler substances through chemical reactions, while elements cannot be broken down further by any means. This makes the correct choice clear.

Carbon dioxide can be represented by the chemical formula CO₂. What does the subscript "2" indicate?

• The number of carbon atoms

• The number of oxygen atoms

• The charge of the molecule

• The mass of the molecule

Answer explanation

In the chemical formula CO₂, the subscript '2' indicates that there are two oxygen atoms present in the molecule. It does not refer to the number of carbon atoms, the charge, or the mass.

Tags

NGSS.MS-PS1-1

A student observes that a substance conducts electricity, has a high melting point, and is malleable. This substance is most likely a:

• Metal

• Nonmetal

• Metalloid

• Noble gas

Answer explanation

The substance conducts electricity, has a high melting point, and is malleable, which are characteristic properties of metals. Nonmetals and noble gases do not conduct electricity, while metalloids have mixed properties.