Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 148 · 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) letting the paper dry (b) dipping the cotton bud (c) putting the iron away (d) reading the message
2. 2.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a balloon (c) white paper (d) a cotton bud
4. 4.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the kind of juice (c) the ironing time (d) how dark the writing is
6. 6.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) reading the message
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) lemon juice (d) an adult with an iron
8. 8.True or false: cutting the lemon is a job a child can do. (a) True (b) False
9. 9.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a battery cell (d) white paper
11. 11.True or false: yeast is needed for the secret lemon message. (a) False (b) True
12. 12.🍋 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
13. 13.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a small bowl (c) lemon juice (d) a cotton bud
15. 15.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
16. 16.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
17. 17.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
19. 19.⚖️ 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 keep it the same (c) we change it
20. 20.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) dipping the cotton bud
21. 21.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
23. 23.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
25. 25.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) the paper ate it (d) dry juice is see-through
26. 26.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) writing turns green (d) it gets darker
27. 27.True or false: white paper is needed for the secret lemon message. (a) True (b) False
28. 28.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: putting the iron away is a job a child can do. (a) True (b) False
30. 30.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
31. 31.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) letting the paper dry (d) cutting the lemon
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) lemon juice (c) an adult with an iron (d) a small bowl
33. 33.⚖️ 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
34. 34.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
35. 35.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) lemon juice (d) a balloon
36. 36.⚖️ 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 same cotton bud
37. 37.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
38. 38.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
39. 39.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
40. 40.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) plugging in the iron (d) reading the message

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