Which change is chemical?(1 point)
Responses
water freezing: liquid water becoming solid water
water freezing: liquid water becoming solid water
water boiling: solid water becoming gaseous water
water boiling: solid water becoming gaseous water
water evaporating: liquid water becoming gaseous water
water evaporating: liquid water becoming gaseous water
water undergoing electrolysis: liquid water becoming oxygen and hydrogen molecules
water undergoing electrolysis: liquid water becoming oxygen and hydrogen molecules
Which number remains unchanged during photosynthesis?(1 point)
Responses
the number of glucose molecules
the number of glucose molecules
the number of carbon atoms
the number of carbon atoms
the number of carbon dioxide molecules
the number of carbon dioxide molecules
the number of water molecules
the number of carbon atoms
In a chemical reaction, which aspect of the reactants changes?(1 point)
Responses
name of each element
name of each element
total mass
total mass
nuclei
nuclei
arrangement of the atoms
arrangement of the atoms
A young snake eats and digests a mouse. The increase in the snake’s mass equals(1 point)
Responses
the mass of the mouse plus the mass of waste produced by the snake.
the mass of the mouse plus the mass of waste produced by the snake.
only the mass of the mouse
only the mass of the mouse
the mass of the mouse minus the mass of waste produced by the snake.
the mass of the mouse minus 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 plus 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?
(1 point)
Responses
6
6
8
8
2
2
4
6
The change that is chemical is water undergoing electrolysis, where liquid water becomes oxygen and hydrogen molecules. This is a chemical change because the chemical composition of water is being altered, resulting in the formation of different substances (oxygen and hydrogen).
To determine which change is chemical from the options provided, we need to understand the difference between physical and chemical changes.
Physical changes involve a change in the physical properties of a substance, such as state (solid, liquid, gas), shape, or size, without any alteration in its chemical composition. Examples of physical changes include water freezing or boiling. In these cases, the water molecules are only rearranging themselves due to changes in temperature, but the actual composition of the substance remains the same.
On the other hand, chemical changes involve a transformation at the molecular level, resulting in the formation of different substances with different chemical properties. These changes are typically accompanied by the breaking of chemical bonds and the formation of new ones. Examples include burning, rusting, and electrolysis.
In the given options, all the changes involve water going through phase changes (freezing, boiling, evaporating), except for the last option, water undergoing electrolysis. Electrolysis is a chemical process where an electric current is passed through water to separate it into its constituent elements, hydrogen and oxygen. Thus, water undergoing electrolysis is the only change that is chemical.