When two or more substances combine, but each keeps its own properties, the new combination is called a(an) a) element b) mixture c) compound d) homogeneous substance

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 is the molarity of the solution produced when 145 g of nacl is dissolved in sufficient water to prepare 2.75 l of solution?

The vapor pressure of ethanol is 1.00 × 102 mmhg at 34.90°c. what is its vapor pressure at 61.61°c? (δhvap for ethanol is 39.3 kj/mol.)