Lesson plan Grade 4 Social Studies & Civics
The Water Hiding in Your Lunch: A Grade 4 Food and Farms Lesson
A grade 4 lesson where students use two published farm-water estimates and multiplication to figure the unseen water in a cookout menu, then compare food choices.
Objectives
- Students will multiply and divide with the published water estimates for beef and wheat to find the water behind a meal.
- Students will compare the water cost of two foods and explain which choice uses less water.
Vocabulary
- Water footprint
- All the water it takes to make the things we use and eat, counting water used far away. A hamburger's water footprint includes the water that grew the cattle's feed.
Also: estimate, irrigation
Teacher overview
Most of the water a family uses never comes out of its faucets, because it is used far away on farms that grow the family's food. Commonly cited Water Footprint Network estimates put the water behind a pound of beef at roughly 1,800 gallons and the water behind a pound of wheat at roughly 220 gallons, and FAO figures put agriculture at roughly 70 percent of global freshwater withdrawals. Most of the beef figure is rainwater used by the pasture and feed crops cattle eat, not irrigation or tap water. This lesson turns those two published estimates into grade 4 multiplication and division practice, then into an economics conversation about the costs behind choices. The common misconception to plan for is that a small or dry-looking food must carry a small water cost; the handout questions are built to show that the water is real even though it was used somewhere else. Write the two estimates on the board before class so students can refer to them all period.
Procedure
Hook (5 min): Hold up or draw a simple lunch: a burger and a bun. Ask students to guess how many gallons of water it took to put that lunch on the table. Record guesses on the board without comment.
Direct instruction (10 min): Introduce the term water footprint: all the water used to grow and make a thing, counted together. Present the two estimates from researchers who study farm water: about 1,800 gallons for a pound of beef and about 220 gallons for a pound of wheat. Explain where the water goes: rain and irrigation water grow the feed crops cattle eat and the wheat in bread, so the water is spent on the farm, long before the store. Model one computation aloud: a half pound of beef is 1,800 divided by 2, which is 900 gallons.
Guided practice (10 min): In pairs, students compute the water behind 2 pounds of wheat, then check with a neighboring pair. Confirm the product, 440 gallons, on the board and have one student explain the multiplication before independent work begins.
Independent practice (15 min): Students complete the six numbered questions on the handout alone. Circulate with one formative question: "Is your answer bigger or smaller than one pound's estimate, and why does that make sense?" Students who cannot say whether a product should be bigger than the starting number need a quick regrouping before the closure.
Closure and exit card (5 min): Each student writes one sentence answering: "Why can a small food carry a big water cost?" Collect and scan for the idea that the water was spent on a farm to grow the food or its feed, not at the table.
Student Handout
Researchers estimate that growing and making one pound of beef takes about 1,800 gallons of water, and that one pound of wheat takes about 220 gallons. Use those two estimates for every question. Use the amounts in each question and show your work.
- A burger patty uses one quarter of a pound of beef. Divide 1,800 by 4. How many gallons of water does the patty stand for?
- A family cookout uses 3 pounds of beef. How many gallons of water went into that beef?
- The same cookout uses 4 pounds of wheat for the buns. How many gallons of water went into the wheat?
- How many more gallons does one pound of beef take than one pound of wheat?
- About how many whole pounds of wheat could be grown with the water it takes to make one pound of beef? Try multiplying 220 by different numbers.
- The cookout beef stands for 5,400 gallons and the buns stand for 880 gallons. How many gallons is that in all?
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
- Answer: 450 gallons. One quarter of 1,800 is 1,800 divided by 4, and 1,800 / 4 = 450 gallons.
- Answer: 5,400 gallons. Three pounds at 1,800 gallons each is 3 x 1,800 = 5,400 gallons.
- Answer: 880 gallons. Four pounds at 220 gallons each is 4 x 220 = 880 gallons.
- Answer: 1,580 gallons. The difference is 1,800 - 220 = 1,580 gallons more for the beef.
- Answer: 8 pounds. 8 x 220 = 1,760 gallons, which fits within 1,800, while 9 x 220 = 1,980 gallons is more than 1,800. So the water for one pound of beef could grow eight whole pounds of wheat, with 40 gallons left over.
- Answer: 6,280 gallons. Adding the two parts gives 5,400 + 880 = 6,280 gallons for the whole cookout.
Differentiation
Support (below grade level)
Allow a multiplication chart or a calculator for questions 2 and 3, and pre-mark the two estimates at the top of the handout in two colors so students pull the right number into each problem. Question 1 can be set up as a shared example before independent work.
Extension (above grade level)
Ask students to design their own cookout menu using only the two given estimates, with at least three items and whole-pound amounts, and to show the total gallons for the menu with all work labeled.
ELL supports
Pre-teach water footprint, estimate, and irrigation with a simple sketch of a field, a sprinkler line, and a plate. Provide a sentence starter for the exit card: "A small food can stand for a lot of water because ___."
Extensions
Have students compare two possible lunches with the same handout estimates, one heavy on beef and one heavy on wheat, and write two sentences saying which lunch uses less farm water and how they know. Keep the focus on the arithmetic comparison rather than telling anyone what to eat.