Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 250 · 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) ironing the paper (b) reading the message (c) plugging in the iron (d) cutting the lemon
2. 2.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
3. 3.🛟 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
4. 4.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
5. 5.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
6. 6.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
7. 7.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
8. 8.🛟 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
9. 9.True or false: putting the iron away is a job a child can do. (a) False (b) True
10. 10.⚖️ 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
11. 11.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
13. 13.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) chemical (c) physical (d) musical
14. 14.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same cotton bud (c) the kind of juice (d) how dark the writing is
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a small bowl (d) turmeric powder
17. 17.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) dipping the cotton bud (d) putting the iron away
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) white paper (d) a cotton bud
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a magnet (c) a small bowl (d) a cotton bud
20. 20.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
21. 21.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
22. 22.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) reading the message (d) letting the paper dry
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) a balloon (d) turmeric powder
24. 24.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
25. 25.True or false: white paper is needed for the secret lemon message. (a) False (b) True
26. 26.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) an adult with an iron (d) white paper
28. 28.True or false: ironing the paper is a job a child can do. (a) False (b) True
29. 29.True or false: writing the message is a job for an adult. (a) True (b) False
30. 30.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
31. 31.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) letting the paper dry (d) cutting the lemon
32. 32.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
33. 33.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) plugging in the iron (d) writing the message
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
35. 35.🍋 Which of these steps is a job a child can do? (a) reading the message (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
36. 36.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
37. 37.True or false: reading the message is a job for an adult. (a) False (b) True
38. 38.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
39. 39.⚖️ 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 ironing time (c) the kind of juice
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False

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