Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 63 · 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.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
2. 2.True or false: ironing the paper is a job for an adult. (a) True (b) False
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the same paper (d) the iron setting
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
5. 5.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
6. 6.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
7. 7.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) an adult with an iron (d) lemon juice
9. 9.⚖️ 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) False (b) True
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
12. 12.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) ironing the paper (d) putting the iron away
13. 13.🛟 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
14. 14.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
15. 15.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
16. 16.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
17. 17.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
18. 18.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
19. 19.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) a balloon (d) a magnet
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the same paper (c) the same cotton bud (d) the kind of juice
21. 21.⚖️ 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 measure it (c) we keep it the same
22. 22.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a magnet
24. 24.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a cotton bud (d) a balloon
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a mirror (d) a small bowl
27. 27.True or false: writing the message is a job for an adult. (a) False (b) True
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) a mirror (d) lemon juice
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) a small bowl (d) a cotton bud
31. 31.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
33. 33.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) lemon juice (d) a small bowl
35. 35.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) reading the message
36. 36.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) reading the message (d) writing the message
37. 37.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
38. 38.True or false: cutting the lemon is a job for an adult. (a) True (b) False
39. 39.⚖️ 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 ironing time
40. 40.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands

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