There are several Science Olympiads and competitions that Class 4 students can participate in to showcase their knowledge and skills in the field of science. These competitions provide a platform for students to engage in practical experiments, problem-solving, and critical thinking. Here are a few notable ones:

1. National Science Olympiad (NSO):
- Conducted by the Science Olympiad Foundation (SOF).
- Tests students' understanding of scientific concepts, logical reasoning, and analytical skills.
- Consists of multiple-choice questions.
- Students can participate through their schools.

2. International Mathematics and Science Olympiad (IMSO):
- Organized by the EduHeal Foundation.
- Tests students' mathematical and scientific aptitude.
- Involves both theoretical and practical examinations.
- Students can participate through their schools.

3. International General Knowledge Olympiad (IGKO):
- Conducted by the Science Olympiad Foundation (SOF).
- Tests students' knowledge in various subjects, including science.
- Consists of multiple-choice questions.
- Students can participate through their schools.

4. International Olympiad of Science (iOS):
- Organized by the SilverZone Foundation.
- Tests students' scientific knowledge and understanding.
- Involves both theory and practical examinations.
- Students can participate through their schools.

5. Unified Council's National Level Science Talent Search Examination (NSTSE):
- Conducted by the Unified Council.
- Tests students' scientific and logical reasoning abilities.
- Consists of multiple-choice questions.
- Students can participate individually.

Participating in these competitions can help Class 4 students develop a deeper understanding of scientific concepts, improve their problem-solving skills, and gain confidence in their abilities. It is important to note that the eligibility criteria, registration process, and exam dates may vary for each competition. Students can visit the respective websites or contact their schools for more information on how to participate.