Matter: Elements, Compounds, and Mixtures Test

What cannot be broken down into other substances?

• Compound

• Mixture

• Solids

• Element

Answer explanation

An element is a pure substance that cannot be broken down into simpler substances by chemical means. Unlike compounds and mixtures, which can be separated into their components, elements are the fundamental building blocks of matter.

Which of the following are not signs of a chemical change?

• Dissolving

• Heat

• Gas/bubble formation

• Formation of precipitate

Answer explanation

Dissolving is a physical change, not a chemical one. It involves the separation of molecules without altering their chemical structure, unlike heat, gas formation, and precipitate formation, which indicate chemical changes.

Rust, pure water and carbon dioxide are all examples of what?

• Compounds

• Elements

• Homogeneous mixtures

• Plasma

Answer explanation

Rust (iron oxide), pure water (H2O), and carbon dioxide (CO2) are all compounds, as they consist of two or more elements chemically bonded together. Therefore, the correct answer is compounds.

If you pour 3 unknown liquids into a graduated cylinder, which one will rise to the top?

• The one with the highest density

• The one with the lowest density

• Whichever one was poured in last

Answer explanation

The liquid with the lowest density will rise to the top when mixed with others, as less dense substances float on denser ones. Therefore, the correct answer is the one with the lowest density.

Mixtures are separated through ___________changes.

• mixture

• compound

• physical

Answer explanation

Mixtures are separated through physical changes, which involve changes in the state or appearance of the substances without altering their chemical composition. This distinguishes them from compounds, which require chemical changes to separate.

Which of the following is NOT a chemical change?

• Dissolving sugar in your coffee

• Milk getting sour

• A metal fence post rusting

• Burning gasoline

Answer explanation

Dissolving sugar in coffee is a physical change, as the sugar can be recovered. In contrast, souring milk, rusting metal, and burning gasoline are chemical changes, resulting in new substances.

Matter is classified into two main groups known as_______.

• solids and fluids

• pure substances and mixtures

• homogeneous and heterogeneous

• elements and compounds

Answer explanation

Matter is classified into two main groups: pure substances, which have a uniform composition, and mixtures, which consist of two or more substances. Thus, the correct answer is pure substances and mixtures.

Pure substances are classified into two groups known as_______________.

• elements and mixtures

• elements and compounds

• heterogeneous and homogeneous

• atoms and elements

Answer explanation

Pure substances are classified into two groups: elements, which are made of one type of atom, and compounds, which are made of two or more types of atoms chemically bonded. Thus, the correct answer is elements and compounds.

What does the following picture represent?

• element

• compound

• mixture of elements

• mixture of compounds and elements

Answer explanation

The picture likely shows a combination of different substances, indicating it is a mixture. Since it includes both elements and compounds, the correct choice is 'mixture of compounds and elements'.

NH3 is a:

• Mixture

• Element

• Compound

• Particle

Answer explanation

NH3, or ammonia, is a compound made up of nitrogen and hydrogen atoms. It has a fixed ratio of these elements, distinguishing it from mixtures and elements, making 'Compound' the correct choice.