Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 310 · 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? Which of these is kept the same? (a) the ironing time (b) the kind of juice (c) how dark the writing is
2. 2.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
3. 3.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
4. 4.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) letting the paper dry (d) writing the message
5. 5.True or false: cutting the lemon is a job a child can do. (a) False (b) True
6. 6.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
7. 7.⚖️ 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 same cotton bud (c) the ironing time (d) the iron setting
8. 8.⚖️ 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
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud (d) the iron setting
10. 10.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) an adult with an iron (d) a balloon
11. 11.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a battery cell (d) a cotton bud
13. 13.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) the iron is brown (d) heat adds colour
14. 14.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) cutting the lemon (d) plugging in the iron
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) white paper (d) yeast
16. 16.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
17. 17.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
18. 18.True or false: white paper is needed for the secret lemon message. (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.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
21. 21.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
22. 22.True or false: writing the message is a job for an adult. (a) True (b) False
23. 23.⚖️ 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
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
25. 25.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a balloon (c) an adult with an iron (d) white paper
27. 27.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
28. 28.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) reading the message (d) plugging in the iron
29. 29.True or false: yeast is needed for the secret lemon message. (a) False (b) True
30. 30.True or false: putting the iron away is a job a child can do. (a) True (b) False
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) a cotton bud (c) white paper (d) lemon juice
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) lemon juice (d) a balloon
33. 33.⚖️ 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) True (b) False
34. 34.⚖️ 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 iron setting
35. 35.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) dipping the cotton bud
36. 36.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) the ink is magnetic (d) it turned into air
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 keep it the same (c) we change it
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) an adult with an iron (c) a cotton bud (d) lemon juice
39. 39.🍋 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) writing the message
40. 40.True or false: reading the message is a job for an adult. (a) True (b) False

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