what kind of chemical reaction is 2Na + I2 → 2NaI Classifying Chemical Reactions – Identify the following reactions as synthesis (S), decomposition (D), single-replacement (SR), double-replacement (DR), acid-base (AB) or combustion (C).

When the water vapor cools it condenses select a number that represents his process on the

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.

What best discribes the relationship between wavelength and frequency in a electromagnetic wave