Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 839 · 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 a mirror for the secret lemon message? (a) not needed (b) needed
2. 2.True or false: plugging in the iron is a job for an adult. (a) False (b) True
3. 3.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown
4. 4.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
5. 5.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
7. 7.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) turmeric powder (d) lemon juice
9. 9.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
10. 10.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) letting the paper dry (d) putting the iron away
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a mirror (d) white paper
12. 12.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
13. 13.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) dipping the cotton bud (d) letting the paper dry
14. 14.🔍 Which is the odd one out? (a) writing the message (b) putting the iron away (c) plugging in the iron (d) cutting the lemon
15. 15.⚖️ 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
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the kind of juice (c) how dark the writing is (d) the same paper
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) yeast (c) a cotton bud (d) white paper
18. 18.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
19. 19.⚖️ 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
20. 20.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
21. 21.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
22. 22.🍋 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
23. 23.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
24. 24.True or false: plugging in the iron is a job a child can do. (a) False (b) True
25. 25.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
26. 26.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
27. 27.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) lemon juice (d) a battery cell
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.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
31. 31.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
32. 32.True or false: ironing the paper is a job a child can do. (a) False (b) True
33. 33.🍋 Which of these steps is a job for an adult? (a) reading the message (b) cutting the lemon (c) writing the message (d) dipping the cotton bud
34. 34.⚖️ 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
35. 35.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
36. 36.⚖️ 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
37. 37.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
38. 38.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a small bowl (c) a cotton bud (d) white paper
40. 40.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a mirror (c) lemon juice (d) a battery cell

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