Lesson plan Grade 2 Math
Muddy Kettle Creek's Trash Screen: A Grade 2 Picture Graph Lesson
Students sort four kinds of litter pulled from a creek trash screen, build a single-unit picture graph, and answer compare questions from the graph.
Objectives
- Students will sort litter cards into four categories and count each category.
- Students will draw a picture graph in which one picture stands for one item.
- Students will answer compare and total questions using only the picture graph.
Vocabulary
Key words: picture graph, category, key, compare, trash screen
Teacher overview
A trash screen is a metal rack set across a channel to catch floating litter before it reaches open water, and the crew that cleans one keeps a count of what comes out. This lesson gives students the counts from a screen on Muddy Kettle Creek in the town of Fennel Bay and asks them to build a picture graph in which one picture stands for exactly one item. The misconception to plan for is that second graders often judge a picture graph by the length of a row rather than by the number of pictures in it, so a row of large drawings looks like more than a longer row of small ones. Insist on same-size pictures and a stated key from the first row onward.
Procedure
Hook (5 min): Show the four sticky note colors and tell students each color stands for one kind of litter pulled from the screen on Muddy Kettle Creek in the town of Fennel Bay: plastic bottles, snack bags, cups, and straws. Ask students to predict which kind the crew found the most of, and write the four predictions on the board.
Build the class picture graph (12 min): Reveal the counts one category at a time: 9 bottles, 6 snack bags, 4 cups, 7 straws. As each count is read, have that many students each place one sticky note of the matching color in a row on the chart paper, lining the rows up so the left edges match. Write the key at the bottom of the chart in words: one note stands for one item. Arrange one row on purpose with the notes spread apart, then ask the class whether spreading them out changed the count.
Model two compare questions (8 min): Using the class chart, model finding how many more bottles than cups by matching pictures one to one and counting the leftovers, then write 9 - 4 = 5 beside the work. Model a total question the same way by combining the cup row and the straw row, recording 4 + 7 = 11. Emphasize that both answers come from counting pictures rather than from measuring row length with fingers.
Handout work (15 min): Distribute the handout, which repeats the four counts and asks students to draw their own picture graph before answering six questions. Circulate and check that each student's pictures are the same size and that the key is written. Ask two students to explain problem 6 aloud, since fewer-than questions reverse the order most students expect.
Closure (5 min): Collect one exit response on an index card: students name the category with the fewest items and write how many items it has. Sort the cards into correct and incorrect piles before dismissal to decide whether the compare work needs another pass tomorrow.
Student Handout
Imagine you are on the crew that cleans the trash screen on Muddy Kettle Creek in the town of Fennel Bay. Here is what the crew found in one week.
| Kind of litter | How many |
|---|---|
| Plastic bottles | 9 |
| Snack bags | 6 |
| Cups | 4 |
| Straws | 7 |
Draw a picture graph with one row for each kind. Draw one small circle for each item. Write the key under your graph: one circle stands for one item. Then answer the questions.
- How many plastic bottles did the crew find?
- The crew found 9 bottles and 4 cups. How many more bottles than cups is that?
- The crew found 4 cups and 7 straws. How many cups and straws is that in all?
- Add all four kinds: 9 bottles, 6 snack bags, 4 cups, and 7 straws. How many items in all?
- Which kind of litter did the crew find the fewest of?
- The crew found 9 bottles and 6 snack bags. How many fewer snack bags than bottles is that?
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: 9 bottles. Students count the circles in the bottle row, which should have exactly nine.
- Answer: 5 bottles. Match cups to bottles one to one and count what is left over: 9 - 4 = 5.
- Answer: 11 items. Combine the two rows: 4 + 7 = 11.
- Answer: 26 items. Add the four counts in order: 9 + 6 = 15, then 15 + 4 = 19, then 19 + 7 = 26.
- Answer: Cups. The cup row has 4 circles, which is fewer than 6, 7, or 9.
- Answer: 3 snack bags. Subtract the smaller count from the larger: 9 - 6 = 3. A student who answers 6 has read the snack bag count instead of the difference.
Differentiation
Support
Provide a graph frame with the four row labels already printed and boxes drawn for each picture, so these students only place one circle in each box. Give them counters to match one to one for problems 2 and 6 before they write a number sentence.
Extension
Ask students to write one new compare question about the graph and trade it with a partner, then check each other's answers against the graph. Students who finish can redraw the same data as a bar graph with a single-unit scale and explain what stayed the same.
ELL supports
Bring in one real example of each category, or a clear photograph of each, and label them before the counting begins. Post sentence frames for the compare questions: "There are ___ more ___ than ___." Teach "fewer" and "more" as a pair with hand gestures, since problem 6 depends on the distinction.
Extensions
Have the class collect the same four categories from the schoolyard for one week, wearing gloves and leaving anything sharp for an adult, tally them daily, and build a second picture graph. Comparing the schoolyard graph with the Muddy Kettle Creek graph gives students a reason to talk about which litter is most likely to wash into a storm drain and reach the creek in the town of Fennel Bay.