Pure Substances and Mixtures Review

A pure substance that cannot be broken down into other substances by chemical or physical means. 

• compound          

• atom

• mixture 

• element

Answer explanation

An element is a pure substance that cannot be broken down into simpler substances by chemical or physical means, unlike compounds and mixtures, which can be separated into their components.

What is an example of a mixture?

• iron

• ice

• soil

• gold

Answer explanation

Soil is a mixture of organic matter, minerals, gases, liquids, and organisms. Unlike pure substances like iron, ice, or gold, which have uniform composition, soil contains various components, making it a clear example of a mixture.

This diagram represents a _____.

• pure substance that is a compound

• mixture of elements

• pure substance that is an element

• mixture of compounds

Answer explanation

The diagram shows a combination of different elements, indicating it is a mixture of elements. This choice is correct as it does not represent a single pure substance or a compound.

Tags

NGSS.MS-PS1-1

In a ______________, one substance is dissolved in another substance.

• solution

• suspension

• colloid

Answer explanation

In a solution, one substance (the solute) is completely dissolved in another substance (the solvent), resulting in a homogeneous mixture. This distinguishes it from suspensions and colloids, where particles do not fully dissolve.

Identify the following substance.

• Element

• Compound

• Mixture

• Diatomic Molecule

Answer explanation

A mixture consists of two or more substances that are physically combined but not chemically bonded. This distinguishes it from elements, compounds, and diatomic molecules, which have specific chemical compositions.

Tags

NGSS.MS-PS1-1

Select all the pure substances below (pick 3).

• element

• compound

• molecule

• mixture

Answer explanation

Elements, compounds, and molecules are pure substances. An element consists of one type of atom, a compound is made of two or more types of atoms chemically bonded, and a molecule is a group of atoms bonded together, all pure forms.

Water

• Pure Substance

• Mixture

Answer explanation

Water is a pure substance because it consists of only one type of molecule (H2O) and has a uniform composition throughout. Unlike mixtures, pure substances have distinct physical and chemical properties.

Coffee

• Pure Substance

• Mixture

Answer explanation

Coffee is a mixture because it contains various components, such as water, coffee grounds, and other compounds, which do not combine chemically. A pure substance consists of only one type of particle, unlike coffee.

Which of the following is a homogeneous mixture?

• Salad

• Saltwater

• Granite

• Trail mix

Answer explanation

Saltwater is a homogeneous mixture because it has a uniform composition throughout, with salt completely dissolved in water. In contrast, salad, granite, and trail mix are heterogeneous mixtures with visibly different components.

Which of these is an example of a pure substance?

• Milk

• Gold

• Air

• Concrete

Answer explanation

Gold is a pure substance because it consists of only one type of atom, making it homogeneous. In contrast, milk, air, and concrete are mixtures containing multiple components.

Tags

NGSS.MS-PS1-4