Unit E: Matter and Its Properties

Why can racecars accelerate faster than other cars?

1. Get Set to Explore

Vocabulary

  • accelerate: To change speed or direction or both.
  • combustion: A chemical reaction in which a compound reacts with oxygen to release energy; water is a byproduct of the reaction.
  • nitromethane: A fuel that contains nitrogen, oxygen, and methane and is used in race cars.

Building Background

  • If you wish, bring in footage of car races to show to the class. Give students an opportunity to share what they know about race cars. During the discussion, emphasize the idea that racecars differ from passenger cars in a number of ways related to speed, handling, and engine performance.
  • Review the definitions of the first two vocabulary words with the class. Ask students to use these words in sentences related to car racing and racecars.
  • Write the word nitromethane on the board. Point out that the prefix nitro- comes from the word nitrogen, but refers to chemical group NO2. Elicit from students that nitro contains oxygen, and make sure students understand that oxygen is needed for any fuel to burn. Review what methane is, referring students to Student Edition page E24, if necessary. Then go over the definition of nitromethane with students.
  • Introduce the Discover! question, and ask students what they think the answer might be. You may wish to explain that the vocabulary words may provide hints. Write students' ideas on the board to refer to later.

2. Guide the Exploration

  • Invite students to launch the Discover! Simulation. Students should spend some time examining the controls and the instruments on the screen. Tell them that they can learn what the controls and instruments do by clicking each. Point out that students control how fast the racecar goes by moving the slider up or down on the gas pedal. Each time they race, they can click the Nitro switch to squirt a set amount of nitromethane into the engine.
  • Suggest that students make a cause-effect chart to record how increasing the gas or adding nitromethane affects the instrument readings. They should also leave space for taking notes on different strategies they tried to improve their time.
  • After students have had some time to race and before they go on to Step 3, return to the Discover! question. Ask volunteers to summarize what they learned about the topic from the simulation. Then, let the class revise, correct, or add to their previous answers posted on the board. Have students complete the simulation.

3. Review/Assess

  • Request that a volunteer read Step 3's Wrap-up aloud to the class. Encourage students to relate what happened in the simulation to the ideas presented in the Wrap-up. Guide students to realize that injecting nitro at the beginning of a race helps a racecar accelerate to its racing speed more quickly, which is helpful for shaving off time during a race. Reinforce the concept that burning any fuel requires oxygen. Point out that with gasoline, the oxygen comes from the air. With nitromethane, the oxygen is part of the fuel itself, which allows the fuel to burn faster and thus, to provide more power. Encourage students to ask any questions they have about the simulation and about the combustion of fuels. Clarify concepts for the class.
  • Direct students to return to the simulation to work on the Extension question. Students should refer to their notes, as well as replay the simulation, to determine the relationship between maximum speed and best time.

If time permits, present students with the following questions:

  • Critical Thinking Classify Is the reaction in which a racecar burns gasoline for fuel endothermic or exothermic? What about the reaction in which the racecar burns nitromethane? For each fuel, explain your answer. Answer: Both are exothermic reactions because both give off heat during combustion.
  • Inquiry Skill Record and Interpret Data Review your data from the simulation, including the speedometer and tachometer readings for different fuels and fuel levels. What relationships do you see? Answer: Students should notice that the greater the speed, the higher the tachometer reading is; they should also note that the speed and tachometer readings are highest when nitromethane is fed to the engine.

4. Reaching All Learners

Challenge

Assign interested students to learn about different fuels used in cars and how these fuels are rated. Students should do a report that includes a chart comparing fuels, their composition, and their rating. They should research alternative as well as conventional fuels. Let students share what they learn with the class.