Which is a physical property of milk?

a)milk has a ph ranging from 6.4 to 6.8.

b)milk spoils when left unrefrigerated over several days.

c)milk boils at about 212°f (100°c).

d)milk curdles when mixed with vinegar.

It's C. Milk boils at about 212 degrees

Option (c) is the correct answer.

Explanation:

Properties which does not affect the chemical composition of a substance are known as physical properties.

For example, mass, melting point, boiling point etc are all physical properties.

When there is change in pH of milk then it means chemical composition of substance has changed.

Also, when milk is spoiled then chemical change has occurred and when milk curdles on mixing vinegar then also chemical composition has changed.

Thus, we can conclude that out of given options milk boils at about 212°F (100°C) represents physical property of milk.

- decrease the number of plants and animals living in the water.

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.