The students in mr. black's class are studying about gases and earth's atmosphere. mr. black placed a deflated soccer ball on the balance. the balance read 560 grams. next mr. black took out a bicycle pump and pumped the soccer ball up until it was nice and round. he put the ball back on the balance and read 570 grams! with this experiment, mr. black just showed his students that air a) has mass. b) has weight. c) takes up space. d) is made up of oxygen and nitrogen.

Asample of tin (ii) chloride has a mass of 0.49 g. after heating, it has a mass of 0.41 g.  what is the percent by mass of water in the hydrate?   %

What is the molecular weight of copper

The picture represents the process that produces most of the energy used by living organisms on earth. which process is represented in the picture? a) the magnetic attraction between two hydrogen nuclei. b) the fusion of hydrogen nuclei to produce a helium nucleus in the core of the sun. c) the fission of hydrogen nuclei to produce a helium nucleus in the core of the sun. d) the chemical reaction between hydrogen nuclei to produce a helium nucleus in earth's atmosphere.