Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 605 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) dark brown words (d) blue words
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) a cotton bud (d) a small bowl
3. 3.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
4. 4.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) a magnet (d) a cotton bud
5. 5.True or false: ironing the paper is a job a child can do. (a) False (b) True
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the kind of juice (c) the ironing time (d) how dark the writing is
7. 7.True or false: plugging in the iron is a job a child can do. (a) True (b) False
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a cotton bud (d) a battery cell
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a balloon (c) a cotton bud (d) a small bowl
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a small bowl (c) a magnet (d) a balloon
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the iron setting (c) how dark the writing is (d) the kind of juice
14. 14.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
15. 15.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) lemon juice (d) turmeric powder
17. 17.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) ironing the paper (d) dipping the cotton bud
18. 18.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is sticky (d) it is cold
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing turns green (d) writing stays faint
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
22. 22.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) putting the iron away (d) plugging in the iron
23. 23.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
24. 24.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
25. 25.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
26. 26.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) chemical (c) physical (d) musical
27. 27.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
28. 28.True or false: putting the iron away is a job a child can do. (a) True (b) False
29. 29.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) putting the iron away (d) cutting the lemon
30. 30.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
31. 31.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
32. 32.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) letting the paper dry
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the iron setting (c) how dark the writing is
35. 35.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a balloon (c) turmeric powder (d) a battery cell
36. 36.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
38. 38.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) cutting the lemon
39. 39.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) paper turns lemony (d) the juice scorches first
40. 40.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False

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