Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 510 · 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.True or false: cutting the lemon is a job for an adult. (a) True (b) False
2. 2.True or false: plugging in the iron is a job a child can do. (a) True (b) False
3. 3.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a magnet (c) a battery cell (d) a mirror
4. 4.⚖️ 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 keep it the same (c) we measure it
5. 5.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
8. 8.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
9. 9.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
10. 10.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a magnet (d) a cotton bud
12. 12.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) dipping the cotton bud (c) letting the paper dry (d) reading the message
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) whoever is fastest (d) any child
14. 14.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) wash your hands (d) lick your fingers
15. 15.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
16. 16.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
17. 17.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
18. 18.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) a rainbow (d) dark brown words
19. 19.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
20. 20.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
21. 21.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
22. 22.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) turmeric powder (d) an adult with an iron
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
25. 25.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
26. 26.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) putting the iron away (d) dipping the cotton bud
27. 27.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a cotton bud (c) a mirror (d) a balloon
28. 28.⚖️ 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
29. 29.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) reading the message (d) dipping the cotton bud
30. 30.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
31. 31.⚖️ 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 same cotton bud (c) the kind of juice (d) how dark the writing is
32. 32.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
33. 33.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
36. 36.⚖️ 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
37. 37.True or false: putting the iron away is a job a child can do. (a) True (b) False
38. 38.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is cold (d) it is sticky
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a magnet (c) a cotton bud (d) an adult with an iron
40. 40.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True

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