Leaf Alchemy Student Worksheet
Science Reading Comprehension
Name: Date: Score:
Earth & Life Science • Informational Text
Leaf Alchemy: The Secret Science of Autumn
Discover the chemistry behind nature's greatest annual color show.
Lexile 740L
1
During spring and summer, deciduous trees look like bustling green food factories. Leaves soak up golden sunlight, water from the soil, and carbon dioxide from the air to perform photosynthesis. The key player in this food-making process is a chemical pigment called chlorophyll. Chlorophyll absorbs red and blue lightwaves but reflects vibrant green light back to our eyes. Because the tree is constantly manufacturing huge amounts of chlorophyll to fuel its growth, this rich green color overpowers every other pigment hiding inside the leaf.
2
As autumn approaches in the Northern Hemisphere, days grow shorter and nights turn crisp and cool. Trees cannot look at a calendar, but they can detect the loss of daylight hours. Deciduous trees realize they will not have enough sunlight or liquid water during freezing winter months to keep their delicate leaves alive. In response, a tree forms a tiny cork-like barrier called an abscission layer across the base of each leaf stem. This barrier slowly pinches off the flow of nutrients and water between the leaf and the rest of the branch.
3
With its water supply choked off, the leaf cannot manufacture new chlorophyll. Sunlight quickly breaks down the remaining green pigment, causing it to disappear. As the green mask vanishes, pigments called carotenoids are finally unveiled. These sunny yellow and orange pigments have actually been inside the leaf all summer long, helping absorb extra sunlight, but were totally masked by chlorophyll. Now, hickory, birch, and ginkgo trees burst into radiant gold and amber.
4
What about dazzling reds and purples? Unlike yellow pigments, red pigments called anthocyanins are not present in summer leaves. When clear autumn days are warm and sunny, leaves continue producing sweet sugars. But chilly nighttime temperatures block those sugars from moving down into the trunk. The trapped sugars react with bright sunlight inside the leaf cell sap, producing vivid scarlet, crimson, and violet hues. Sugar maples and sumacs produce the brightest reds after warm, sunny days followed by cool, crisp nights!
5
Eventually, the cork barrier seals completely, and gusty autumn winds snap the fragile stem. The fallen leaves carpet the forest floor, where soil microbes break them down into rich nutrients for next spring. By shedding its leaves, the tree safely enters dormancy, saving precious moisture until warm sunshine returns.
Key Scientific Terms:
Chlorophyll: Green food pigment Carotenoid: Yellow/orange pigment Anthocyanin: Red/purple pigment Dormancy: Winter rest stage
Leaf Alchemy Reading Passage • Page 1 of 2 Turn over for comprehension questions
Reading Comprehension Check
Student Name: Date:
Directions: Refer back to "Leaf Alchemy: The Secret Science of Autumn" to answer Questions 1–4. Reread carefully before selecting your answers.
Question 1 (Text Evidence • Paragraph 2) 1 Point
According to the passage, why do deciduous trees begin shutting down leaf production in autumn?
A Shorter daylight hours signal that there will not be enough sunlight and liquid water in winter.
B Strong autumn winds blow away the soil nutrients before tree roots can absorb them.
C Forest animals consume the green chlorophyll to store up fats before winter hibernation.
Question 2 (Key Details • Paragraph 3) 1 Point
How are yellow and orange colors (carotenoids) different from red and purple colors (anthocyanins)?
A Yellow and orange pigments are absorbed directly from falling autumn raindrops.
B Yellow and orange pigments were already inside the leaf all summer, hidden under green chlorophyll.
C Yellow and orange pigments only form when nighttime temperatures drop below freezing.
Question 3 (Cause & Effect • Paragraph 4) 1 Point
What weather conditions produce the brightest red and crimson leaves in autumn?
A Warm, sunny days combined with cool, crisp nights that trap plant sugars inside leaves.
B Continuous dark cloudy skies and heavy rainfall that flood the root system.
C Early winter snowstorms that instantly freeze the green chlorophyll onto branches.
Question 4 Short Answer Written Response
3 Points
Imagine a friend claims: "Leaves change color because cold autumn weather paints them from the outside." Explain why this claim is incorrect using at least two scientific details from the passage about how leaves reveal or create their autumn colors.
Self-Check: ☐ Answered Q1–Q3 (A, B, C) ☐ Included 2 text details in Q4 ☐ Complete sentences
Page 2 of 2
Leaf Alchemy Answer Key
Teacher Assessment Resource • Master Answer Key
Leaf Alchemy: The Secret Science of Autumn Total: 6 Points
Comprehension Key & Scoring Rubric
Standard: CCSS.ELA-LITERACY.RI.4.1 / RI.5.1 (Text Evidence & Scientific Explanations)
Q1 A
Q2 B
Q3 A
Q4 3 pts
Section 1: Multiple Choice Detailed Rationales
Question 1: Why deciduous trees shut down leaf production Correct: A
Rationale: Paragraph 2 explicitly notes: "Trees cannot look at a calendar, but they can detect the loss of daylight hours. Deciduous trees realize they will not have enough sunlight or liquid water during freezing winter months..." Distractors B and C mention wind blowing away soil nutrients or animals eating chlorophyll, which are scientifically false and not mentioned in the text.
Question 2: Yellow/orange pigments (carotenoids) vs. red pigments Correct: B
Rationale: Paragraph 3 explains that carotenoids "have actually been inside the leaf all summer long... totally masked by chlorophyll." Paragraph 4 contrasts this by stating red pigments (anthocyanins) are newly created in autumn from trapped sugars. Distractor A (raindrops) and C (freezing temps alone) are fabricated distractors.
Question 3: Ideal weather conditions for bright red foliage Correct: A
Rationale: Paragraph 4 confirms that "Sugar maples and sumacs produce the brightest reds after warm, sunny days followed by cool, crisp nights" because sunny days promote sugar production while cool nights trap sugars in the leaf cells to form anthocyanins. Distractor B and C contradict the text.
Section 2: Question 4 Short Answer Rubric (3 Points Total)
Score Point Scoring Criteria & Performance Indicators
3 Points Exemplary Directly disproves the "cold paints them" claim. Cites at least two accurate scientific details from the text: (1) internal pigments (carotenoids) were already there and get revealed when green chlorophyll breaks down; (2) red pigments (anthocyanins) are synthesized inside the leaf cell sap when trapped sugars react with sunlight. Uses clear, complete sentences.
2 Points Proficient Correctly explains that the color change comes from inside the leaf rather than external painting, but provides only one specific scientific detail (e.g., mentions unmasking carotenoids but leaves out trapped sugars/anthocyanins, or vice versa).
1 Point Developing States that the claim is incorrect, but offers vague or circular reasoning (e.g., "The tree just changes color on its own") without referencing specific chemical pigments or text evidence.
Leaf Alchemy Teacher Guide
Instructional Facilitation Plan • Grades 3–5
45 Minutes Informational Reading
Teacher Directions
Teaching "Leaf Alchemy: The Secret Science of Autumn"
Guide students through close informational reading, scientific cause-and-effect, and evidence-based writing.
CCSS RI.4.1 • RI.5.1 NGSS 4-LS1-1 • 5-PS1-4
Core Learning Targets
- Students will identify the biological cause of leaf color changes in autumn using text evidence.
- Students will contrast pre-existing leaf pigments (carotenoids) with newly synthesized pigments (anthocyanins).
- Students will craft a short constructed response refuting an everyday scientific misconception.
Materials Needed
- Leaf Alchemy Student Worksheet (Pages 1 & 2)
- Highlighters (yellow & green)
- Master Answer Key
Step-by-Step Lesson Architecture (45 Minutes)
1 Hook & Vocabulary Activation (7 Minutes) Whole Class
The "Disappearing Green" Hook: Hold up a fresh green leaf and a colorful autumn leaf (or show photos). Ask: "Where did the green go, and did the red paint come from the sky or from inside the tree?" Briefly preview the 3 key pigment terms on the board: Chlorophyll (green sugar maker), Carotenoid (hidden yellow/orange), and Anthocyanin (newly formed red/purple).
2 Close Reading & Targeted Annotation (15 Minutes) Choral / Partner Read
Read the passage aloud chorally or with designated reading pairs. Guide students to apply a 2-step annotation strategy:
• Box the trigger events: Shorter daylight hours, cork barrier formation (Paragraph 2).
• Underline pigment origins: Highlight where yellow was already hiding (Paragraph 3) versus how red is newly made from trapped sugars (Paragraph 4).
3 Comprehension Check & Written Response (18 Minutes) Independent Practice
Students transition to Page 2. Have students complete Questions 1–3 independently. Before Question 4, remind students to use the R-A-C-E strategy (Restate, Answer, Cite evidence, Explain). Circulate with the Answer Key to check that students reference at least two concrete facts from the text.
4 Debrief & Science Synthesis (5 Minutes) Turn & Talk Exit
Have students share their Question 4 rebuttal with an elbow partner. Call on one volunteer who highlighted carotenoids and one who highlighted anthocyanins to construct the ultimate class summary sentence.
Support & Scaffolding (ELL / Developing)
