Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 54 · 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.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) dipping the cotton bud (d) cutting the lemon
2. 2.True or false: putting the iron away is a job for an adult. (a) True (b) False
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a mirror (c) a small bowl (d) a battery cell
4. 4.⚖️ 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) the iron setting
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a mirror (d) white paper
6. 6.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) dry juice is see-through (d) the ink is magnetic
7. 7.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
8. 8.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
10. 10.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
11. 11.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
13. 13.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) a cotton bud (c) lemon juice (d) white paper
15. 15.True or false: putting the iron away is a job a child can do. (a) False (b) True
16. 16.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
17. 17.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
19. 19.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) turmeric powder (c) a small bowl (d) a cotton bud
21. 21.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) writing the message (c) dipping the cotton bud (d) reading the message
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the iron setting
24. 24.True or false: white paper is needed for the secret lemon message. (a) False (b) True
25. 25.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
26. 26.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
27. 27.True or false: ironing the paper is a job for an adult. (a) True (b) False
28. 28.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) dipping the cotton bud
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) an adult with an iron (d) a balloon
30. 30.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
32. 32.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
33. 33.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
34. 34.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
35. 35.True or false: plugging in the iron is a job for an adult. (a) True (b) False
36. 36.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
37. 37.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
39. 39.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
40. 40.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False

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