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Lesson plan Grade 7 Science

Kirkwell River Spill: Hours Until It Reaches Standale's Intake

A 50-minute grade 7 science lesson where students convert a river's current to miles per hour, find a spill's travel time, and plan sampling before the intake closes.

Objectives

  1. Students will convert a river current from feet per second to miles per hour.
  2. Students will calculate how long a spill takes to travel a stated distance downstream.
  3. Students will explain why river speed drives the decision to close a drinking water intake.

Vocabulary

Key words: current, velocity, intake, unit rate, travel time, sampling station

Teacher overview

A town that draws its drinking water from a river depends on warning time when something spills upstream, meaning enough hours to close the intake and run on stored water until the contaminated stretch of river has gone by. This lesson puts students in that decision, using a tanker crash upstream of the fictional town of Standale on the Kirkwell River. A common misconception in this lesson is that the size of the spill decides the response, when in practice the river's speed and the distance to the intake set the deadline first, and the arithmetic here makes that ordering visible.

Procedure

Hook (5 min): Tell students that a truck carrying fuel has gone off a bridge 12 miles upstream of the intake that supplies the town of Standale. Ask what the operators need to know first. Write every suggestion on the board and circle the ones that involve time or distance.

Direct instruction (12 min): Define current, velocity, intake, and travel time. Show that a speed measured in feet per second becomes miles per hour in two steps: multiply by 3,600 seconds in an hour, then divide by 5,280 feet in a mile. Model the conversion once with a number that does not appear on the handout, using 2.2 feet per second, which gives 7,920 feet per hour and about 1.5 miles per hour. Then show that travel time equals distance divided by speed, and explain that operators also need a fixed block of time to switch the plant onto stored water.

Guided practice (12 min): Work handout items 1 through 3 with the class. Insist that students write the unit on every line, since the conversion is where units usually go missing. Ask one pair to explain why dividing by 5,280 makes the number smaller.

Independent practice (13 min): Students complete handout items 4 through 9 on their own, then trade papers with a partner and check only the units before checking the arithmetic.

Closure and exit ticket (8 min): Each student writes one sentence answering: "Two spills happen at the same place on the same river. One is twice as large as the other. Do the operators have more warning for either one?" Collect the tickets. The expected reasoning is that warning time depends on distance and current, not on spill size. If fewer than three quarters of the class says so, reteach the travel-time relationship before moving on.

Kirkwell River Spill: Hours Until It Reaches Standale's Intake — Grade 7 Science
Name: ____________________________ Date: ______________

Student Handout

The Kirkwell River, the town of Standale, and every number below are fictional and were written for this exercise. Label the units in every step.

  1. A gauge on the Kirkwell River measures the current at 1.8 feet per second. There are 3,600 seconds in an hour. How many feet does the water travel in one hour?
  2. Water traveling 6,480 feet per hour is moving how many miles per hour? There are 5,280 feet in a mile. Round to the nearest tenth.
  3. A spill enters the river 12 miles upstream of Standale's intake. The water moves 1.2 miles per hour. How many hours will the spill take to reach the intake?
  4. The spill takes 10 hours to reach the intake, but nobody reported it until 2 hours after the crash. How many hours are left before the spill arrives?
  5. Operators need 3 hours to close the intake and switch the plant onto stored water. They have 8 hours of warning. How many extra hours of margin do they have?
  6. The response team wants a sampling station every 1.5 miles along the 12 miles between the crash site and the intake, with a station at each end. How many stations is that?
  7. A sample taken 2 miles below the crash measured 45 ppb of fuel compounds. A sample taken 8 miles below measured 9 ppb. What is the percent decrease between the two results?
  8. Standale's intake pumps 1,400 gpm. How many gallons does it pump in 3 hours?
  9. Explain why the operators care more about the river's speed than about the exact number of gallons spilled when they decide whether to close the intake.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 6,480 feet per hour.
    1.8 feet per second times 3,600 seconds per hour equals 6,480 feet per hour.
  2. Answer: 1.2 miles per hour.
    6,480 feet per hour divided by 5,280 feet per mile equals about 1.227, which rounds to 1.2 miles per hour.
  3. Answer: 10 hours.
    12 miles divided by 1.2 miles per hour equals 10 hours of travel time.
  4. Answer: 8 hours.
    The spill needs 10 hours to arrive and 2 of those hours have already passed, so 10 minus 2 leaves 8 hours.
  5. Answer: 5 hours.
    8 hours of warning minus the 3 hours the switch takes leaves 5 hours of margin.
  6. Answer: 9 stations.
    12 miles divided by 1.5 miles equals 8 spaces between stations. A station at both ends of 8 spaces means 8 plus 1, or 9 stations.
  7. Answer: 80 percent.
    45 ppb minus 9 ppb is a drop of 36 ppb. 36 divided by 45 equals 0.8, a decrease of 80 percent.
  8. Answer: 252,000 gallons.
    3 hours equals 180 minutes, and 1,400 gpm times 180 minutes equals 252,000 gallons.
  9. Answer: Speed and distance set the deadline for acting.
    The river's speed and the distance to the intake decide how many hours the operators have before contaminated water arrives, and that deadline does not change with the size of the spill. A larger spill may take longer to pass and may need more stored water, but the closing decision has to be made on the travel-time clock. Accept any answer connecting current and distance to the time available.

Differentiation

Support

Provide a conversion strip for items 1 and 2 that shows the two steps in order with the units printed above each blank. Give students a number line marked in miles from the crash site to the intake so item 6 can be counted rather than divided.

Extension

Ask students to redo item 3 for a spring flood, when the current runs at 3 miles per hour, and to write a short recommendation about whether the sampling plan in item 6 still gives crews enough time to reach every station before the spill passes.

ELL supports

Pre-teach "current," "upstream," "downstream," and "intake" with a simple sketch of a river, an arrow for flow direction, and a labeled pipe. Provide the sentence frame for item 9: "The operators need to know the river's speed because ___."