Which change is chemical?

water boiling

water undergoing electrolysis***

water freezing

water evaporating

Which number remains unchanged during photosynthesis?

the number of carbon atoms***

the number of water molecules

the number of glucose molecules

the number of carbon dioxide molecules

In a chemical reaction, which aspect of the reactants changes?

mass***

total mass

atoms

nuclei

A young snake eats and digests a mouse. The increase in the snake’s mass equals

the mass of the mouse plus the mass of waste produced by the snake.

the mass of the mouse plus the original mass of the snake.

the mass of the mouse.

the mass of the mouse minus the mass of waste produced by the snake.***

Cellular respiration transforms glucose and oxygen into carbon dioxide, water, and energy.



C6H12O6 + 6O2 → 6CO2 + ?H2O + Energy



Based on the law of conservation of matter, what is the missing coefficient for water?

4

6***

2

8