There are several online resources and supplementary materials available for the Science textbook of Class 7. These resources can help students to enhance their understanding of the concepts, provide additional practice, and offer interactive learning experiences. Here are some of the online resources that can be beneficial for students:

1. EduRev:
EduRev is an online platform that offers a wide range of educational resources for various subjects, including Science. It provides access to study materials, practice questions, sample papers, and interactive quizzes. EduRev also offers a community where students can engage in discussions and seek help from experts.

2. NCERT Official Website:
The National Council of Educational Research and Training (NCERT) has an official website where students can find supplementary materials for Science and other subjects. They provide additional exercises, question banks, and exemplar problems that can help students in their studies.

3. YouTube Channels:
There are several YouTube channels dedicated to teaching Science concepts to Class 7 students. These channels provide video lessons, experiments, and demonstrations that make learning more engaging and interactive. Some popular channels include "Science with BrainCafé" and "DronStudy.com."

4. Online Practice Platforms:
There are various online platforms that offer practice tests and quizzes specifically designed for Class 7 Science. These platforms provide a wide range of questions to test students' knowledge and understanding of the subject. Some popular platforms include "TopperLearning" and "Meritnation."

5. Mobile Apps:
There are also mobile applications available for Class 7 Science that provide interactive lessons, quizzes, and games. These apps can be installed on smartphones or tablets, allowing students to access learning materials anytime, anywhere. Some recommended apps include "BYJU'S - The Learning App" and "Class 7 Science App by Meritnation."

These online resources and supplementary materials can be extremely helpful for students to reinforce their learning, practice concepts, and clarify any doubts they may have. It is important for students to explore these resources and utilize them effectively to enhance their understanding of Science.