How can the rate of a reaction be decreased? lowering the amount of reactants

having more surface area

adding a catalyst

raising the temperature

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.

catya that's not even a b or c