Sometimes when matter is combined,_a chemical occurs causing molecules in the mixture to change. For example, mixing baking soda and vinegar together causes a reaction that cannot be_ ; a new substance is made. Even though the original matter (baking soda and vinegar) has changed, the mass of the new matter will remain the same. This phenomenon is known as " _", which states that matter can be changed chemically, but the total_ of the products will remain the same. Another example of how this law works is when steel wool_ . This happens when iron chemically reacts with_ and changes form. In a closed system, the mass of these two elements (uncombined) would be equal to the mass of the rusted product (combined). In a closed system, a chemical reaction creates a new substance when the atoms of the original substances reassemble in new arrangements.

1.) which of the following is a molecule but not a compound? a.he b.f2 c.h2o d.ch4 2.) what is a physical combination of substances? a.a compound b.a molecule c.a mixture d.an element 3.) what is a chemical combination of substances? a.a compound b.an atom c.a mixture d.an element 4.) what is the relationship between the solute and solvent in a solution? a.they form a compound b.they form a mixture c.they form molecules d.they form chemical bonds 5.) the gases in air dissolve in water. what would be one way to reduce the amount of a gas dissolved in water? a.add more water b.reduce the air pressure c.increase the air pressure d.stir the water 6.) how would you determine the solubility of a substance? a.find how well it dissolved various substances. b.find the mass and the volume of the substance. c.find the temperature at which the substance evaporated. d.find how much i was able to dissolve in a solute. 7.) the periodic table organizes all of the kinds of a.molecules. b.compounds. c.atoms. d.ions. 8.)what distinguishes two substances combined to become a compound vs. two substances combined to become a mixture? a.whether they can be easily separated b.whether they chemically bond together c.whether they both are visible d.whether they are heterogeneous 9.) the principle components of air are: n2 78% o2 21% ar 0.95% co2 0.038% this is a solution of a.molecules and atoms. b.molecules. c.compounds and molecules. d.atoms.