Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 115 · 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? What do we do with “the ironing time”? (a) we measure it (b) we keep it the same (c) we change it
2. 2.True or false: letting the paper dry is a job for an adult. (a) True (b) False
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
4. 4.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
5. 5.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) putting the iron away (d) dipping the cotton bud
6. 6.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
7. 7.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
8. 8.🛟 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
9. 9.⚖️ 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 iron setting
10. 10.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
11. 11.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
12. 12.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
13. 13.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) writing turns green (d) it gets darker
14. 14.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) lemon juice (c) a mirror (d) yeast
15. 15.True or false: ironing the paper is a job for an adult. (a) True (b) False
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
17. 17.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
18. 18.⚖️ 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
19. 19.True or false: letting the paper dry is a job a child can do. (a) True (b) False
20. 20.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) ironing the paper (d) letting the paper dry
21. 21.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a balloon (d) a small bowl
22. 22.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
23. 23.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
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) True (b) False
25. 25.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) dipping the cotton bud (c) writing the message (d) reading the message
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
27. 27.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) a small bowl (d) white paper
29. 29.⚖️ 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
30. 30.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
32. 32.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) dry juice is see-through (d) the ink is magnetic
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) a cotton bud (d) white paper
34. 34.⚖️ 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
35. 35.True or false: lemon juice 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) letting the paper dry (c) reading the message (d) plugging in the iron
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) a small bowl (d) an adult with an iron
38. 38.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) white paper (d) a small bowl
40. 40.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) writing the message (d) ironing the paper

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