Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 705 · 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.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
2. 2.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
3. 3.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) any child (d) whoever is fastest
6. 6.⚖️ 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
7. 7.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) it turned into air (d) dry juice is see-through
8. 8.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony
9. 9.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) yeast (d) lemon juice
11. 11.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
12. 12.True or false: putting the iron away is a job a child can do. (a) True (b) False
13. 13.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) a battery cell (d) lemon juice
15. 15.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) lemon juice (d) a cotton bud
17. 17.⚖️ 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 keep it the same (c) we measure it
18. 18.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) chemical (d) musical
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a balloon (c) a cotton bud (d) white paper
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) a balloon (d) a cotton bud
21. 21.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
22. 22.⚖️ 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
23. 23.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
26. 26.True or false: reading the message is a job for an adult. (a) True (b) False
27. 27.🔮 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
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) an adult with an iron (d) yeast
29. 29.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) yeast (c) an adult with an iron (d) a small bowl
31. 31.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) ironing the paper (c) letting the paper dry (d) writing the message
32. 32.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
33. 33.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
34. 34.⚖️ 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
35. 35.⚖️ 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 iron setting (c) how dark the writing is
36. 36.⚖️ 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
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) a battery cell (d) a cotton bud
38. 38.🔍 Which is the odd one out? (a) cutting the lemon (b) reading the message (c) ironing the paper (d) plugging in the iron
39. 39.⚖️ 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
40. 40.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) letting the paper dry (d) dipping the cotton bud

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