Molecules and Compounds

Why is it impossible to see molecules with the naked eye?

• they are too big
• they are too small
• they are too fast
• they have no mass

Which of these compounds has the most atoms?

• CO2
• C6,H12,O6
• O2
• Na,Cl,He,O3

The separation of ions that occurs when an ionic compound dissolves in a solution is known as

• association
• dissociation
• associative principle
• molecular association

At room temperature, oxygen is a gas and hydrogen is a gas.  When they combine, they form a 

• solid
• liquid
• gas
• solution

A water molecule contains

• one hydrogen atom and two oxygen atoms
• two hydrogen atoms and one oxygen atom
• two hydrogen atoms and two oxygen atoms
• two hydrogen atoms and no oxygen atoms

___________ are completely different from the elements they are made of.

• compounds
• atoms
• elements
• ions

Sodium can burn and chlorine can kill you. When they combine into a molecule, the new substance is

• a solid that is safe to touch
• an explosive solid that must be handled carefully
• a combination of gasses that can be deadly
• a neutral gas that is safe to breathe

The formula CO represents one __________ of carbon monoxide.

• atom
• molecule
• ion
• isotope

A molecule of H2,S,O4 contains how many atoms?

• 3
• 6
• 7
• 8

Table salt dissolves in water. What happens when saltwater is made?

• the salt crystals sink to the bottom of the water
• the ionic compound (salt) breaks into pieces
• the salt crystals float to the top of the water
• the water molecules split into ions