Practice: Chemical Reaction?

Name:

1. What two substances react with each other when a candle burns?

• the wick and oxygen
• the wax and oxygen
• the wick and carbon dioxide
• the wax and water

2. When a candle burns, the reaction produces:

• oxygen and water
• carbon dioxide and wax
• wax and oxygen
• carbon dioxide and water vapor

3. If a burning candle is a chemical reaction, why does the flame go out when a jar is placed over the candle?

4. In the chemical equation above, what does the little “2” mean in CO₂?

• there are two CO₂ molecules
• there are two carbon atoms in a CO₂ molecule
• there are two oxygen atoms in a CO₂ molecule
• there are two CO molecules

5. In the chemical equation above, what does "2" in front of "2H₂O" stand for?

• two water molecules are produced for every one methane that reacts
• four hydrogen atoms are produced for every one methane that racts
• two hydrogen molecules are produced for every one methane that reacts

6. In the animation, where do the atoms come from that make the carbon dioxide and the water on the right side of the equation?

7. If you count the number of each type of atom in the reactants (left side of the equation) and count the number of each type of atom in the products (right side of the equation), you will find that:

• they are almost equal
• they are very unequal
• they are equal

8. Are atoms created or destroyed in a chemical reaction?

• Yes, some atoms are created as others are destroyed.
• No atoms are created or destroyed. The atoms simply rearrange themselves and form new molecules.

9. In a physical change, like changing state from a solid to a liquid, the substance itself doesn’t really change. For example, solid water (ice) melts and becomes liquid water. How is a chemical change different from a physical change?