Penny says that dust particles in space cannot be pulled together by the force of gravity because dust particles have very little mass. Ella says that as long as dust particles have mass at all, the force of gravity can pull dust particles toward each other. Which claim identifies who has the better argument and explains the reasoning?

Start an single atom tab. observe the decay of polonium-211. after each decay, press the reset nucleus button to watch the process again. write a description of alpha decay for po-211

15. which of the following is not human-caused groundwater pollution? a. water in an aquifer dissolves elements such as arsenic and mercury from surrounding rock. b. water in an aquifer is contaminated by leachate that seeps into the ground from a landfill. c. water in an aquifer becomes polluted with chemicals used in hydraulic fracturing, or fracking. d. water in an aquifer absorbs harmful bacteria from the drainage field of a septic tank.

The equation below shows a chemical reaction. a + b + heat —> c + d according to the law of conservation of energy, which statement is true? a. the reactants absorb heat because they have less energy than the products. b. the products release heat because they have more energy than the reactants. c. the reactants generate heat because they have more energy than the products. d. the products require heat to form because they have less energy than the reactants.