Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 892 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
2. 2.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a mirror (c) lemon juice (d) an adult with an iron
4. 4.True or false: plugging in the iron is a job for an adult. (a) True (b) False
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) turmeric powder (c) an adult with an iron (d) lemon juice
6. 6.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) green (d) blue
8. 8.⚖️ 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
9. 9.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
10. 10.🧺 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) lemon juice
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) an adult with an iron (d) yeast
12. 12.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) ironing the paper
13. 13.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) no, it stays brown (d) yes, if shaken
14. 14.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
15. 15.🍋 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
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) True (b) False
17. 17.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) yeast (c) a magnet (d) a mirror
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) turmeric powder (c) a cotton bud (d) lemon juice
19. 19.⚖️ 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) the same cotton bud (c) the ironing time (d) the same paper
20. 20.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) whoever is fastest (c) any child (d) the youngest child
21. 21.⚖️ 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
22. 22.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) a magnet (d) yeast
23. 23.True or false: putting the iron away is a job a child can do. (a) False (b) True
24. 24.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
25. 25.True or false: cutting the lemon is a job a child can do. (a) False (b) True
26. 26.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
27. 27.⚖️ 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
28. 28.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
29. 29.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
30. 30.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) almost nothing (d) dark brown words
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
32. 32.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a small bowl (c) lemon juice (d) an adult with an iron
34. 34.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same paper (c) how dark the writing is (d) the kind of juice
36. 36.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) dipping the cotton bud (d) reading the message
37. 37.True or false: reading the message is a job for an adult. (a) False (b) True
38. 38.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
39. 39.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
40. 40.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) writing the message

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