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Irreversible Changes Investigation

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Irreversible Changes Investigation

At the fishing harbour, Hudson, Lachlan and Chloe are helping sort out evidence from a science investigation. Read the investigation notes, then use evidence to decide which changes are irreversible. Do not heat or handle chemicals yourself.

Investigation notes

The harbour team recorded four changes. A: an ice cube melted into water. B: a clean iron hook was left damp in salty air; days later, a reddish-brown coating appeared. C: an egg was cooked in a pan; its clear liquid turned white and firm. D: a small piece of paper was burned safely by a trained adult; smoke and ash remained.

Spot the evidence

Use the investigation notes above for Questions 1–4.

1.Which recorded change is reversible by cooling the material, and why?

2.Which two recorded changes produced a reddish-brown coating or combustion products such as smoke and ash? Choose the best answer.

A and B
B and C
B and D
A and C

3.Chloe says, “The colour change on the hook proves by itself that rusting happened.” Is her conclusion fully supported? Explain what other evidence would make it stronger.

4.True or false: A change is irreversible only if it happens quickly.

TrueFalse

Plan a fair test

Hudson wants to investigate whether salty water makes iron rust faster than fresh water. Answer Questions 5–8 as a scientist planning a safe investigation.

5.Fill in the blanks: The factor Hudson changes on purpose is the . The change he measures is the .

6.Name two conditions Hudson should keep the same to make the comparison fair.

7.Choose the safest and most reliable plan.

Use one nail in each water type, then decide from memory which looks rustier.
Use several identical iron pieces in each water type, label the containers, and compare them at set times without touching the rust.
Use different-sized pieces and change the water each day.
Taste the water and scrape the rust to check what it is.

8.Lachlan notices that the salty-water samples have more reddish-brown coating after five days. Write a conclusion that answers the investigation question and refers to this evidence.

Explain the change

Use your science vocabulary: reversible, irreversible, evidence, and new substance.

9.Explain why cooking an egg is an irreversible change. Include one observation from the notes and explain why cooling cannot return it to its original raw state.

10.A damp paper towel dries in the sun. Is this change reversible or irreversible? Explain how this differs from burning paper.