Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 346 · 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.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
2. 2.⚖️ 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
3. 3.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) writing the message (d) ironing the paper
4. 4.⚖️ 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
5. 5.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) a magnet (d) lemon juice
7. 7.True or false: writing the message is a job for an adult. (a) False (b) True
8. 8.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) putting the iron away (d) ironing the paper
9. 9.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, if cooled (d) yes, in the dark
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a magnet (c) a cotton bud (d) white paper
11. 11.True or false: a small bowl is not 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) lemon juice (b) a cotton bud (c) an adult with an iron (d) turmeric powder
13. 13.⚖️ 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
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a mirror (d) a cotton bud
15. 15.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
16. 16.⚖️ 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
17. 17.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
18. 18.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) green (d) brown
20. 20.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
21. 21.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
22. 22.True or false: ironing the paper is a job a child can do. (a) True (b) False
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
24. 24.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
26. 26.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) dipping the cotton bud (c) reading the message (d) writing the message
27. 27.True or false: plugging in the iron is a job for an adult. (a) True (b) False
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) yeast (d) a cotton bud
29. 29.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
30. 30.🍋 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) plugging in the iron
31. 31.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the juice scorches first (d) the iron is brown
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 measure it (b) we keep it the same (c) we change it
33. 33.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
34. 34.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) any child (d) only an adult
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) how dark the writing is (c) the same paper (d) the kind of juice
36. 36.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
37. 37.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
38. 38.⚖️ 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) True (b) False
39. 39.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
40. 40.⚖️ 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

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