Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 33 · 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 is needed for the secret lemon message? (a) white paper (b) a magnet (c) a balloon (d) yeast
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
3. 3.True or false: putting the iron away is a job a child can do. (a) True (b) False
4. 4.⚖️ 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
5. 5.⚖️ 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 measure it (c) we change it
6. 6.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
7. 7.🍋 Which of these steps is a job a child can do? (a) writing the message (b) ironing the paper (c) putting the iron away (d) cutting the lemon
8. 8.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) reading the message
9. 9.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) reading the message (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) an adult with an iron
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) an adult with an iron (c) white paper (d) a small bowl
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
13. 13.🍋 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
14. 14.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
16. 16.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
17. 17.True or false: plugging in the iron is a job a child can do. (a) False (b) True
18. 18.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a balloon (c) turmeric powder (d) yeast
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) a balloon (d) an adult with an iron
20. 20.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
21. 21.🛟 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
22. 22.True or false: plugging in the iron is a job for an adult. (a) True (b) False
23. 23.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
24. 24.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the ironing time (c) the same cotton bud (d) the kind of juice
26. 26.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) yeast (d) lemon juice
28. 28.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
29. 29.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
30. 30.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is sticky (d) it is cold
31. 31.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) rub your eyes (d) skip washing
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a magnet (d) a cotton bud
33. 33.⚖️ 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) True (b) False
34. 34.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
35. 35.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
36. 36.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
37. 37.⚖️ 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 change it (c) we keep it the same
38. 38.🔮 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
39. 39.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the paper ate it (c) the ink is magnetic (d) it turned into air
40. 40.⚖️ 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

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