During a phase change, mass

a: stays the same
b: increases
c: decreases
d: increases, then decreases

Stays the same, within a closed system.

Your teacher has probably used this example before. When you heat water in a pot on the stove, as it starts to boil, the water evaporates and turns into steam. 
If you have two pots that are both heating on the stove, filled to the same water level; one is covered with an air-tight lid, and the other is left open.The water level in the open pot will be lower, because more steam was able to escape during a gaseous phase. 

All of the food energy that passes between organisms comes from the Sun. You

might be wondering how this is possible. After all, humans can’t eat sunlight! Plants

and other organisms that use sunlight absorb it and then use that energy to make

their own food. That energy passes to other organisms that eat the plants. For

example, grass uses sunlight to make food. A deer gets energy by eating the grass.

After that, a wolf gets energy by eating the deer.

The movement of food energy from one

organism to another is called a food chain. Take

a look at the food chain on the right. The arrows

show how food energy is passed from one

organism to the other. The plants use energy

from the Sun to make their own food. Both

antelopes and squirrels get energy by eating

plants. The hawk gets energy by eating the

squirrels. Mountain lions and coyotes get energy

from eating the antelopes.

You might think the arrows in a food chain show which organism is eating another

organism. The arrows actually show how energy is moving through the food chain.

Explanation: