Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 640 · 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) yeast (d) white paper
2. 2.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) dipping the cotton bud (d) plugging in the iron
3. 3.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
4. 4.True or false: putting the iron away is a job for an adult. (a) True (b) False
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
6. 6.⚖️ 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
7. 7.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) ironing the paper
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
9. 9.🍋 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
10. 10.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
11. 11.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we keep it the same (c) we change it
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a mirror (c) an adult with an iron (d) a small bowl
14. 14.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air
15. 15.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
16. 16.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
17. 17.🧺 Do we need a small bowl 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 same cotton bud”? (a) we keep it the same (b) we change it (c) we measure it
19. 19.True or false: letting the paper dry is a job a child can do. (a) False (b) True
20. 20.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) white paper (c) a small bowl (d) a cotton bud
22. 22.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
23. 23.True or false: putting the iron away is a job a child can do. (a) True (b) False
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
25. 25.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
26. 26.⚖️ 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) how dark the writing is (c) the same paper
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
28. 28.True or false: letting the paper dry is a job for an adult. (a) True (b) False
29. 29.🧺 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) an adult with an iron
30. 30.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
31. 31.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
32. 32.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
34. 34.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) reading the message (d) cutting the lemon
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
36. 36.True or false: writing the message is a job for an adult. (a) False (b) True
37. 37.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) writing the message (c) dipping the cotton bud (d) letting the paper dry
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a battery cell (d) a cotton bud
39. 39.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
40. 40.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True

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