Exploring Properties of Matter

Which of the following is an example of a physical property of matter?

• Flammability

• Density

• Reactivity with acid

• Ability to rust

Answer explanation

Density is a physical property that describes how much mass is contained in a given volume. In contrast, flammability, reactivity with acid, and ability to rust are chemical properties, as they involve changes in the substance's chemical structure.

Which of the following is a chemical property of matter?

• Melting point

• Boiling point

• Reactivity with oxygen

• Density

Answer explanation

Reactivity with oxygen is a chemical property, as it describes how a substance interacts with another substance. In contrast, melting point, boiling point, and density are physical properties.

Which of the following is a pure substance?

• Air (O2, N2, CO2...)

• Saltwater (NaCl + H2O)

• Carbon dioxide (CO2)

• Soil

Answer explanation

A pure substance consists of only one type of particle. Carbon dioxide (CO2) is a pure substance made up solely of CO2 molecules, while air, saltwater, and soil contain multiple components.

Which of the following is a mixture?

• Water (H₂O)

• Sodium chloride (NaCl)

• Brass (Cu + Zn)

• Carbon dioxide (CO₂)

Answer explanation

Brass (Cu + Zn) is a mixture of copper and zinc, retaining the properties of both metals. In contrast, water (H2O), sodium chloride (NaCl), and carbon dioxide (CO2) are pure substances with fixed compositions.

Which of the following is an example of a homogeneous mixture?

• Sand and water

• Oil and water

• Salt dissolved in water

• Salad

Answer explanation

A homogeneous mixture has a uniform composition throughout. Salt dissolved in water forms a solution where the salt is evenly distributed, making it homogeneous. In contrast, sand and water, oil and water, and salad are heterogeneous mixtures.

Which of the following is an example of a heterogeneous mixture?

• Vinegar

• Air

• Milk

• Salad

Answer explanation

A heterogeneous mixture consists of visibly different substances. Salad contains various ingredients like lettuce, tomatoes, and dressing that can be seen and separated, making it a clear example of a heterogeneous mixture.

Which of the following statements is true about elements and compounds?

• Elements can be broken down into simpler substances by chemical means.

• Compounds are made up of two or more elements chemically combined.

• Elements are made up of two or more compounds chemically combined.

• Compounds cannot be broken down into simpler substances by chemical means.

Answer explanation

The correct statement is that compounds are made up of two or more elements chemically combined. Elements cannot be broken down by chemical means, and compounds can be broken down into simpler substances.

Tags

NGSS.MS-PS1-5

Which of the following is an example of a physical change?

• Burning wood

• Rusting iron

• Melting ice

• Baking a cake

Answer explanation

Melting ice is a physical change because it involves a change in state from solid to liquid without altering the chemical composition. In contrast, burning wood, rusting iron, and baking a cake involve chemical changes.

Tags

NGSS.MS-PS1-4

Which of the following is an example of a chemical change?

• Dissolving sugar in water

• Cutting paper

• Freezing water

• Digesting food

Answer explanation

Digesting food is a chemical change because it involves breaking down food into simpler substances, altering its chemical structure. In contrast, dissolving sugar, cutting paper, and freezing water are physical changes.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following best describes a compound?

• A substance made of two or more elements physically combined.

• A substance made of two or more elements chemically combined.

• A mixture of two or more substances.

• A pure element.

Answer explanation

A compound is defined as a substance formed when two or more elements are chemically combined, resulting in a new substance with distinct properties. The correct choice accurately reflects this definition.