The science curriculum used in 8th grade in the United States typically encompasses a broad range of topics, including life science, physical science, and Earth and space science. Commonly, students study topics such as cells, ecosystems, matter and energy, motion and force, and the solar system. The curriculum aims to build upon foundational knowledge from previous grades and introduce more complex concepts.

The choice of curriculum in 8th grade science is influenced by various factors, including state standards, local school district policies, and the preferences of individual teachers. According to the National Science Teachers Association (NSTA), the most widely used curricula include those from major publishers such as Glencoe/McGraw-Hill, Houghton Mifflin Harcourt, and Pearson. These curricula are designed to align with the Next Generation Science Standards (NGSS), which were developed to provide a clear and consistent framework for K-12 science education across the United States.

The NGSS emphasize three-dimensional learning, which integrates disciplinary core ideas, scientific practices, and cross-cutting concepts. In 8th grade, the focus is on the following disciplinary core ideas:

1. Life Science: Cells, heredity, and evolution.

2. Physical Science: Matter and energy, motion and force, and waves and their interactions with matter.

3. Earth and Space Science: Earth's systems, the solar system, and the universe beyond.

Data from the National Center for Education Statistics (NCES) indicate that approximately 80% of 8th-grade science classrooms in the United States use curricula aligned with the NGSS. This alignment is crucial for ensuring that students receive a comprehensive and coherent science education that prepares them for future learning and career opportunities. The NGSS also emphasize the importance of inquiry-based learning, which encourages students to engage in scientific practices such as observing, experimenting, and analyzing data.

In conclusion, the science curriculum used in 8th grade in the United States is diverse but generally follows a structured framework that includes life science, physical science, and Earth and space science. The adoption of the NGSS has helped standardize the curriculum and ensure that students receive a well-rounded science education.