Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 400 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the iron setting (c) the same paper (d) the kind of juice
3. 3.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
5. 5.⚖️ 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
6. 6.⚖️ 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 change it (c) we keep it the same
7. 7.True or false: ironing the paper is a job a child can do. (a) True (b) False
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) lick your fingers (d) rub your eyes
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) lemon juice (d) turmeric powder
10. 10.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
11. 11.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the juice scorches first (d) the iron is brown
12. 12.🍋 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
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a battery cell (c) a cotton bud (d) white paper
14. 14.True or false: ironing the paper is a job for an adult. (a) True (b) False
15. 15.⚖️ 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
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 keep it the same (c) we change it
17. 17.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the iron setting (c) the same paper (d) how dark the writing is
19. 19.⚖️ 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 keep it the same (c) we measure it
20. 20.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
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 steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
23. 23.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
24. 24.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
25. 25.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) cutting the lemon (c) letting the paper dry (d) reading the message
26. 26.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) a small bowl (d) a balloon
28. 28.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
30. 30.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
31. 31.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) lemon juice (c) a cotton bud (d) white paper
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) a magnet (d) yeast
34. 34.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) ironing the paper (c) letting the paper dry (d) reading the message
35. 35.⚖️ 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 ironing time
36. 36.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
37. 37.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
38. 38.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
39. 39.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
40. 40.True or false: reading the message is a job for an adult. (a) True (b) False

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