By Mukesh 
The CBSE Class 10th Science Board Exam 2026 was successfully conducted today, 25 February 2026, in offline mode across various exam centres affiliated with the Central Board of Secondary Education (CBSE). Students can now check the CBSE Class 10 Science unofficial answer key 2026 here, along with a detailed paper analysis, difficulty level, and section-wise review. The unofficial answer key will be released today around 2:00 PM after the exam
CBSE Class 10 Science Exam 2026 – Key Highlights
- Board: Central Board of Secondary Education (CBSE)
- Class: 10th
- Subject: Science
- Exam Date: 25 February 2026
- Exam Timing: 10:30 AM to 1:30 PM (3 hours)
- Reporting Time: 10:00 AM
- Question Paper Type: Theory (80 marks)
- Internal Assessment: 20 marks
- Mode of Exam: Offline (Pen and Paper)
- Unofficial Answer Key: Expected at 2:00 PM (today)
CBSE Class 10 Science Answer Key 2026 (Unofficial) – Release Time
The CBSE Class 10 Science paper ended at 1:30 PM and students will be able to access the unofficial answer key for all sets around 2:00 PM. Coaching institutes and subject experts will solve the question paper and provide a set-wise solution PDF and video explanation for students
Students can use this unofficial answer key to:
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Estimate their probable marks before the official CBSE answer key and result.
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Cross-check objective and short-answer questions.
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Analyse their performance and plan upcoming board exams accordingly.
CBSE Class 10 Science 2026 Answer Key (All Sets)
8. Assertion & Reason
Assertion (A): Blood plasma transports carbon dioxide in dissolved form, while oxygen is transported by respiratory pigments.
Reason (R): Carbon dioxide is more soluble in water than in oxygen.
Answer: Assertion (A) is true, but Reason (R) is false.
Explanation: While the Assertion is scientifically accurate, the Reason is phrased incorrectly. Carbon dioxide is more soluble in water than oxygen is in water; comparing its solubility to “oxygen” itself is a logical error.
9. Assertion & Reason
Assertion (A): There are generally a greater number of individuals at the lower trophic levels of an ecosystem.
Reason (R): The greatest number is of the producers.
Answer: Both (A) and (R) are true and (R) is the correct explanation of (A).
Explanation: In most ecosystems, the pyramid of numbers is upright. Producers (the lowest trophic level) must be the most numerous to provide enough energy to support the fewer consumers above them.
10. Descriptive Questions
(a) Hormonal Regulation
Statement: “The timing and the amount of hormone secreted by a gland are regulated in the human body.”
Justification: This is regulated by a feedback mechanism.
Example: When blood glucose levels rise, the pancreas detects this change and secretes insulin to lower the sugar levels. Once the levels fall to a normal range, the secretion of insulin is reduced or switched off.
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(b) Limitations of Electrical Impulses
While electrical impulses are fast, they have two primary limitations:
Limited Reach: Electrical impulses reach only those cells that are connected by nervous tissue; they cannot reach every single cell in the body.
Recovery Time: Once an electrical impulse is generated and transmitted, the cell needs time to reset its mechanisms before it can generate a new impulse. This means cells cannot continuously create and transmit impulses.
11. Survival and Variation
Statement: “Variation is useful for the survival of species over time.”
Explanation: Environments change constantly (temperature shifts, water level changes, etc.). If a population is identical and the environment changes drastically, the entire species could be wiped out. Variation ensures that some individuals might possess traits that allow them to survive the change.
Example: In a population of bacteria living in temperate waters, most might die if the water temperature increases due to global warming. However, a few heat-resistant variants would survive and regrow the population.
Question 30: Negative Magnification Greater than OneThe correct option is (A) Concave mirror; Nature of image – real.
Reasoning:Sign of Magnification ($m$): In optics, a negative magnification signifies that the image is real and inverted.Magnitude ($|m| > 1$): A magnification greater than one means the image is enlarged (magnified).Mirror Type: * A convex mirror always produces virtual, erect, and diminished images ($m$ is always positive and less than 1).A concave mirror can produce a real, inverted, and enlarged image when the object is placed between the center of curvature ($C$) and the principal focus ($F$).
Question 31: Spectrum Sequence from Top to BottomThe correct option is (B) Red, Yellow, Green, Blue, Violet.
Reasoning:When white light passes through a glass prism, it splits into its constituent colors (VIBGYOR).Refraction/Bending: Different colors bend by different amounts. Red light has the longest wavelength and bends the least, while Violet light has the shortest wavelength and bends the most.Position on Screen: Because Red bends the least, it appears at the top of the spectrum. Because Violet bends the most, it appears at the bottom.The sequence from top to bottom is Red, Orange, Yellow, Green, Blue, Indigo, and Violet. Option (B) follows this specific descending order correctly.
CBSE Class 10 Science Exam Pattern 2026
The CBSE Class 10 Science paper 2026 carried a total of 80 marks for theory and 20 marks for internal assessment, as per the latest CBSE exam pattern 2025–26. The Science paper is designed to test conceptual understanding, application-based learning, and competency-based skills in Physics, Chemistry, and Biology.
Marking Scheme and Weightage
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Theory Exam: 80 marks
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Internal Assessment: 20 marks (periodic tests, practical work, projects, portfolio)
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Duration: 3 hours (10:30 AM – 1:30 PM)
According to the latest CBSE guidelines, the Science theory syllabus is divided into the following major units:
How to Use the CBSE Class 10 Science Unofficial Answer Key 2026
Once the unofficial answer key for CBSE Class 10 Science 2026 is published around 2:00 PM, students can follow these steps to calculate their expected marks:
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Keep your Science question paper and OMR/answer sheet with you.
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Match your responses with the set-wise unofficial answer key provided by experts.
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For MCQs and assertion–reason questions, award 1 mark for each correct answer, without negative marking.
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For short and long answers, compare with detailed solutions to estimate partial marks based on CBSE marking scheme.
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Add the scores section-wise (Physics, Chemistry, Biology) to get your total out of 80.
This will help you predict your performance before the official result declaration and identify areas of improvement for upcoming subjects.
CBSE Class 10 Science 2026 – Official Answer Key and Result
The answer key released at 2:00 PM will be unofficial and meant only for immediate reference. The official CBSE Class 10 Science answer key 2026 (if released publicly) will be provided later on the CBSE academic/board portal along with instructions for evaluation.
Final marks will be based on:
Students are advised not to panic if there is a slight mismatch between unofficial and official solutions, as examiners may follow step-wise marking and allow equivalent answers.