Which change is chemical?(1 point)
Responses
water freezing: liquid water becoming solid water
water boiling: solid water becoming gaseous water
water undergoing electrolysis: liquid water becoming oxygen and hydrogen molecules
water evaporating: liquid water becoming gaseous water
water undergoing electrolysis: liquid water becoming oxygen and hydrogen molecules
Which number remains unchanged during photosynthesis?(1 point)
Responses
the number of water molecules
the number of carbon atoms
the number of carbon dioxide molecules
the number of glucose molecules
the number of carbon atoms
In a chemical reaction, which aspect of the reactants changes?(1 point)
Responses
arrangement of the atoms
name of each element
nuclei
total mass
arrangement of the atoms
A young snake eats and digests a mouse. The increase in the snake’s mass equals(1 point)
Responses
only the mass of the mouse
only the mass of the mouse
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 minus the mass of waste produced by the snake.
the mass of the mouse plus the original mass of 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
8
6
4
2
6
To determine which change is chemical, we need to understand the difference between physical changes and chemical changes.
Physical changes involve a change in the state or appearance of a substance, but the composition remains the same. Examples include changes in state like freezing or boiling.
Chemical changes, on the other hand, involve a transformation of the substance's chemical composition. New substances are formed with different properties compared to the original substance.
Now, let's analyze the given responses:
1. Water freezing: This is a physical change where liquid water transitions into solid water (ice). The composition of water remains the same, only its state changes.
2. Water boiling: Similar to freezing, this is a physical change where liquid water turns into gaseous water (water vapor). Again, the composition of water remains unchanged.
3. Water undergoing electrolysis: This is a chemical change. Electrolysis is a process that uses an electric current to break down water molecules (H2O) into their constituent elements, oxygen (O2) and hydrogen (H2). As a result, new substances are formed with different properties from the original water.
4. Water evaporating: This is also a physical change. Evaporation occurs when liquid water changes into water vapor at a temperature below boiling point. The composition of water remains the same; only its state changes.
Based on the above analysis, the chemical change is option 3: water undergoing electrolysis.