Atoms, Elements & Molecules

You have a sample of a substance that you cannot physically separate into components. You also cannot chemically separate that substance into components. Which of the following are true about your sample?

• The sample is made up of one type of atom.

• The sample is made up of multiple elements

• The sample is made up of a single element

• The sample is made up of several types of atoms

Answer explanation

An element is a substance than cannot be separated into simpler substances by chemical changes.

An atom is the smallest unit of an element that has the same chemical properties and behave similarly

Air _______ (is/is not) a pure substance because it is made up of more than one type of matter.

Answer explanation

A pure substance is a sample of matter that has specific chemical and physical properties, such as appearance, melting point, and reactivity. It is always made of the same material- NOT A MIXTURE.

Which of the following components of air is a compound?

• carbon dioxide CO₂

• Oxygen O₂

• Nitrogen N₂

• Argon Ar

Answer explanation

A compound is a substance made up of two or more different types of atoms joined by chemical bonds.

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Which of the following can be observed from the model of water?

• Water is a molecule

• Water is a compound

• Water is made up of three types of atoms

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Another way to model water is with letters and lines is like this: H-O-H. What is one way that these two models are different?

• They show different types and numbers of atoms

• The atoms are connected in a different order

• The chemical bonds are represented differently

• One model clearly shows a repeating pattern

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Based on the models of white and red phosphorus, the white phosphorus is a:

• simple molecule

• extended structure

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Based on the models of white and red phosphorus, the red phosphorus is a:

• simple molecule

• extended structure

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Based on the models of white and red phosphorus, BOTH are examples of:

• compound

• element

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The structure of carbon tetrachloride, CCl₄, is similar to the structure of carbon tetrabromide, CBr₄. Both molecules have four atoms connected to a central carbon atom. Does that mean the two substances have the same properties?

• Yes, because molecules with similar structures must have the same properties.

• Yes, because the carbon atom determines the properties of both substances.

• No, because the types of atoms in a molecule and its structure both influence the properties of a substance.

Which statements are true about molecules and compounds? Select all that apply.

• Molecules are made of one atom and compounds are made of two or more atoms

• Some molecules are also compounds

• Molecules are always composed of two or more elements

• Compounds are always composed of two or more elements.

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