Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 734 · 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 of these steps is a job for an adult? (a) ironing the paper (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
2. 2.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
3. 3.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a balloon (c) an adult with an iron (d) a small bowl
6. 6.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) cutting the lemon (d) dipping the cotton bud
7. 7.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
8. 8.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
9. 9.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
10. 10.⚖️ 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 change it (c) we measure it
11. 11.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
12. 12.True or false: letting the paper dry is a job for an adult. (a) False (b) True
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) yeast (d) an adult with an iron
14. 14.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
15. 15.True or false: ironing the paper is a job a child can do. (a) False (b) True
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
17. 17.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) a battery cell (d) white paper
18. 18.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
19. 19.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) an adult with an iron (d) white paper
21. 21.⚖️ 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
22. 22.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) a mirror (d) an adult with an iron
23. 23.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) reading the message
24. 24.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) putting the iron away (d) reading the message
25. 25.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
27. 27.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) lemon juice (d) a small bowl
29. 29.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) lemon juice (c) white paper (d) an adult with an iron
31. 31.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
32. 32.True or false: ironing the paper is a job for an adult. (a) True (b) False
33. 33.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
34. 34.🔮 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
35. 35.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
36. 36.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the same cotton bud (c) the kind of juice (d) the ironing time
38. 38.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) ironing the paper
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the same cotton bud (c) the kind of juice (d) the same paper
40. 40.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) cutting the lemon (d) letting the paper dry

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