5 What substance would do the best job of cleaning pots and
pans?
A
A substance with a pH of 7
B
A substance with a pH of 2
C
A substance with a pH of 4
D
A substance with a pH of 8

D . A substance with a pH of 8

Explanation:

pH stands for "Potential for Hydrogen." This is an indicator of a solution's acidity or alkalinity. It is also used to tell which chemicals are great for cleaning.

pH 7 and pH 8 are both considered "neutral pH," thus, solutions with these pH are often used as dishwashing detergents because they do not destroy the surfaces of objects. However, pH 8 is said to be more alkaline in nature. This allows it to destroy the residues, such as fats and oils, in pots and pans. It is the pH of baking soda.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.