Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 168 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a balloon (d) a cotton bud
2. 2.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) how dark the writing is (c) the same paper (d) the same cotton bud
4. 4.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
5. 5.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) dark brown words (d) a rainbow
6. 6.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
7. 7.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) an adult with an iron (d) a balloon
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
9. 9.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
10. 10.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
12. 12.⚖️ 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
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) white paper (d) a battery cell
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) turmeric powder (d) white paper
16. 16.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) a battery cell (d) yeast
17. 17.True or false: yeast is needed for the secret lemon message. (a) True (b) False
18. 18.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
19. 19.🍋 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
20. 20.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) yeast (d) a small bowl
21. 21.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) writing stays faint (d) the paper floats
22. 22.🔮 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
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the same paper (c) how dark the writing is (d) the kind of juice
24. 24.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) cutting the lemon (d) plugging in the iron
25. 25.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
26. 26.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
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.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
30. 30.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
31. 31.⚖️ 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 keep it the same (c) we measure it
32. 32.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) putting the iron away (d) writing the message
33. 33.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
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 is the odd one out? (a) ironing the paper (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
36. 36.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
37. 37.True or false: plugging in the iron is a job a child can do. (a) False (b) True
38. 38.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a cotton bud (d) turmeric powder
40. 40.⚖️ 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

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