Consider the unbalanced chemical equation hf + al -> alf3 + h2. when coefficients are added to balance the equation, which two substances have a coefficient of two? a. hf
b. alf3
c. h2
d. al

This line graph compares the growth of plants that were kept in the sun for different amounts of time.a)  on day 7, the plants kept in the sun for 3 hours were how tall? b)  on day 7, the plants kept in the sun for 6 hours were how tall? c)    on day 10, the plants kept in the sun for 9 hours were how tall? d)  on day 11, the plant that was grown with 1 hour of sunlight was how tall? e)  based on the graph, the plant grows best in what amount of sunlight?

In a laboratory experiment, a fermenting aqueous solution of glucose and yeast produces carbon dioxide gas and ethanol. the solution was heated by burning natural gas in a bunsen burner to distill the ethanol that formed in the flask. during the distillation, the ethanol evaporated and then condensed in the receiving flask. the flame of the burner was kept too close to the bottom of the flask and some of the glucose decomposed into a black carbon deposit on the inside of the flask. during this experiment the following changes occurred. which of these changes involved a physical change and not a chemical change? check all that apply. 1-condensation of ethanol 2-evaporation of ethanol 3- formation of carbon dioxide gas from glucose burning of natural gas 4-formation of ethanol from glucose by yeast 5-formation of a carbon deposit inside the flask

Stage in which a star’s outer layers have started to cool and grow outward?