Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 852 · 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.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a mirror (c) a small bowl (d) a cotton bud
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the kind of juice (c) how dark the writing is (d) the iron setting
3. 3.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) putting the iron away (d) writing the message
4. 4.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
5. 5.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
6. 6.True or false: white paper is needed for the secret lemon message. (a) False (b) True
7. 7.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
8. 8.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) dry juice is see-through (d) it turned into air
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
10. 10.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
11. 11.True or false: ironing the paper is a job for an adult. (a) False (b) True
12. 12.🔮 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
13. 13.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
14. 14.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
15. 15.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
16. 16.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
17. 17.True or false: ironing the paper is a job a child can do. (a) True (b) False
18. 18.⚖️ 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
19. 19.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
20. 20.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
21. 21.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) yeast (c) a battery cell (d) an adult with an iron
22. 22.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) turmeric powder (d) a cotton bud
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) lemon juice (c) white paper (d) a cotton bud
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) a small bowl (d) turmeric powder
27. 27.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
29. 29.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
30. 30.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) a mirror (d) white paper
32. 32.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) reading the message
33. 33.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) white paper (d) lemon juice
35. 35.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) putting the iron away (d) plugging in the iron
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) a cotton bud (d) a small bowl
37. 37.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
38. 38.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
39. 39.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
40. 40.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True

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