Mod J Unit 1 Lesson 3 - Molecules and Extended Structures

Which of these substances is a compound? 

• Carbon (C)

• Chlorine (Cl)

• Oxygen (O)

• Ammonia (NH₃)

If you were to look at grains of table salt (sodium chloride, NaCl) with a magnifying glass, you would see that each grain is a little cube. Why are salt grains cubical?

• All extended structure compounds form cubes.

• Sodium and chlorine atoms both have cubical shapes.

• In the extended structure of NaCl, atoms are arranged in a cubical pattern.

• A molecule of NaCl contains eight atoms, each at one of the corners of a cube.

Sucrose is composed of carbon, oxygen, and hydrogen. Which statement best describes the properties of sucrose?

• They are exactly like the properties of carbon (C).

• They are exactly like the properties of oxygen (O).

• They are exactly like the properties of hydrogen (H).

• They are different from the properties of carbon, oxygen, and hydrogen.

A molecule of methanol is composed of carbon atoms connected to 3 hydrogen atoms and a hydroxide group. A hydroxide group is made up of an oxygen atom bonded to a hydrogen atom. How many different types of atoms make up one molecule of methanol?

• 3

• 4

• 5

• 6

These models show the arrangement of particles in two solid materials. Which statement describes a basic difference between these materials?

• X is a metal, and Y is a salt.

• X is an element, and Y is a compound.

• X is a crystal, and Y is made of separate molecules.

• X is made of single atoms, and Y is made of molecules.

Reactant A and reactant B react to form product C. What type of substance is product C?

• an atom

• mixture

• element

• compound

Polyvinyl chloride (PVC) is a polymer used to make water pipes and other products. Polymer molecules are made of groups of atoms that repeat many times in long chains as shown in the formula.

Which circle, left to right, shows the repeating group of atoms that forms PVC?

• the first (1st) circle

• the second (2nd) circle

• the third (3rd) circle

• the fourth (4th) circle

Which of the following can be observed from the model of water? Select two (2) that apply.

• water is a molecule

• water is a compound

• water is made of 3 types of atoms

Answer explanation

Water is a molecule (two or more atoms held together by chemical bonds). Water is also a compound (the water particle is made up of two or more different types of atoms). A molecule of water consists of three atoms, but only two types of atoms: hydrogen and oxygen.

Another way to model water is with letters and lines 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 forces holding the atoms together are represented differently.

• One model clearly shows a repeating pattern

Answer explanation

Because both models represent water, they both have the same type and number of atoms connected in the same way. The main difference is how they show the chemical bonds. In the model

H – O – H

the chemical bonds are represented by lines, but in the pictured model, there are no lines. The atoms are touching each other to show that there is an attractive force between them.

Look carefully at the models of white phosphorus and red phosphorus. Based on the models of these structures, white phosphorus is a(n) _______ and the red phosphorus is a(n) _______.

• element ; compound

• simple molecule;

  extended structure

• extended structure;

  simple molecule