Question

post - lab questions: for each of the following activities, decide if it is an example of a physical or chemical change. provide justification for your choice: 1. a log burning on the fire change: justification: 2. boiling water change: justification: 3. frying an egg change: justification: 4. an iron pipe rusting change: justification: 5. an iceberg melting change: justification: 6. fruit rotting change: justification: 7. shredding cheese change: justification: 8. a pond freezing change: justification:

Explanation:

Step1: Recall definitions

A physical change is a change in which the substance's physical form changes but its chemical composition remains the same. A chemical change results in the formation of a new substance with a different chemical composition.

Step2: Analyze log - burning

A log burning on the fire is a chemical change. Wood (carbon - based compounds) reacts with oxygen to produce carbon dioxide, water vapor and ash. New substances are formed.
Change: Chemical change
Justification: Wood reacts with oxygen to form new substances like CO₂, H₂O and ash.

Step3: Analyze boiling water

Boiling water is a physical change. Water changes from the liquid state to the gaseous state (steam). The chemical composition of water (H₂O) remains the same.
Change: Physical change
Justification: Only state change from liquid to gas, no new chemical substances formed.

Step4: Analyze frying an egg

Frying an egg is a chemical change. Proteins in the egg white and yolk denature due to heat, forming new substances with different chemical properties.
Change: Chemical change
Justification: Proteins denature to form new substances.

Step5: Analyze iron - pipe rusting

An iron pipe rusting is a chemical change. Iron (Fe) reacts with oxygen and water in the air to form iron oxide (rust, Fe₂O₃·xH₂O). A new substance is formed.
Change: Chemical change
Justification: Iron reacts with O₂ and H₂O to form iron oxide.

Step6: Analyze ice - berg melting

An iceberg melting is a physical change. Ice (solid water) changes to liquid water. The chemical composition of water (H₂O) does not change.
Change: Physical change
Justification: Only state change from solid to liquid, no new chemical substances formed.

Step7: Analyze fruit - rotting

Fruit rotting is a chemical change. Microorganisms break down the organic compounds in the fruit, producing new substances such as acids, alcohols and gases.
Change: Chemical change
Justification: Microorganisms break down organic compounds to form new substances.

Step8: Analyze pond - freezing

A pond freezing is a physical change. Water changes from the liquid state to the solid state (ice). The chemical composition of water (H₂O) remains unchanged.
Change: Physical change
Justification: Only state change from liquid to solid, no new chemical substances formed.

Answer:

1. Change: Chemical change

Justification: Wood reacts with oxygen to form new substances like CO₂, H₂O and ash.

1. Change: Physical change

Justification: Only state change from liquid to gas, no new chemical substances formed.

1. Change: Chemical change

Justification: Proteins denature to form new substances.

1. Change: Chemical change

Justification: Iron reacts with O₂ and H₂O to form iron oxide.

1. Change: Physical change

Justification: Only state change from solid to liquid, no new chemical substances formed.

1. Change: Chemical change

Justification: Microorganisms break down organic compounds to form new substances.

1. Change: Physical change

Justification: Only physical form change, no new chemical substances formed.

1. Change: Physical change

Justification: Only state change from liquid to solid, no new chemical substances formed.