Chemical reactions that occur when substances are mixed can be identified by the emergence of substances with different properties; the total mass of substances when a reaction occurs remains the same.
Stars range greatly in size and distance from Earth, and this can explain their relative brightness.
Earth's orbit and rotation and the orbit of the moon around Earth cause observable patterns, such as length and direction of shadows, day and night, and the seasonal appearance of some stars in the night sky.
Four major Earth systems interact. Rainfall helps to shape the land and affects the types of living things found in a region. Water, ice, wind, organisms, and gravity break rocks, soils, and sediments into smaller pieces and move them around. The geosphere, biosphere, hydrosphere, and/or atmosphere interact.