Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 999 · 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.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
2. 2.⚖️ 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
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a small bowl (c) a balloon (d) turmeric powder
4. 4.⚖️ 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
5. 5.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
6. 6.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) lemon juice (c) a battery cell (d) a balloon
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) the paper floats (d) writing stays faint
8. 8.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
9. 9.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) letting the paper dry
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
11. 11.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) writing the message (d) ironing the paper
12. 12.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
13. 13.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
14. 14.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
15. 15.⚖️ 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 measure it (c) we keep it the same
16. 16.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) putting the iron away (d) dipping the cotton bud
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we change it (c) we measure it
19. 19.⚖️ 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 cotton bud
20. 20.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
21. 21.True or false: ironing the paper is a job a child can do. (a) True (b) False
22. 22.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
23. 23.🍋 Which of these steps is a job for an adult? (a) writing the message (b) cutting the lemon (c) reading the message (d) dipping the cotton bud
24. 24.⚖️ 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) the ironing time (c) how dark the writing is
25. 25.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
26. 26.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) green (d) brown
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
29. 29.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) putting the iron away
30. 30.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
32. 32.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
33. 33.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) yeast (d) a cotton bud
34. 34.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) any child (d) whoever is fastest
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
36. 36.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
37. 37.🧺 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) a cotton bud (d) lemon juice
38. 38.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
39. 39.⚖️ 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
40. 40.True or false: writing the message is a job for an adult. (a) False (b) True

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