Which is a clue that a chemical change has occured?
a. a beaker suddenly becomes very warm when you mix two room-temperature liquids in it.
b. a liquid forms bubbles when it reaches a high temperature.
c. water changes color when you add food coloring to it.
d. a car door feels hot if you touch it on a summer afternoon.

What can be said about farmers in highly developed countries? a) they have little or no negative impact on the environment. b) they practice subsistence agriculture. c) they are able to incorporate polyculture into their farming practices. d) they utilize organic farming techniques on a regular basis. e) they rely on large amounts of energy from fossil fuels.

Which animal is a producer in this ecosystem

Draw the farm's ppf for corn and beef. draw a point that shows an inefficient combination of corn and beef. label ita. draw a point that shows an unattainable combination of corn and beef. label itb. draw a point that shows an efficient combination of corn and beef. label itc.