Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 312 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
2. 2.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) letting the paper dry (d) reading the message
3. 3.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) the paper ate it (d) dry juice is see-through
4. 4.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
5. 5.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) putting the iron away (d) cutting the lemon
6. 6.True or false: writing the message is a job a child can do. (a) False (b) True
7. 7.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
8. 8.🧺 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 small bowl (d) turmeric powder
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a balloon (c) lemon juice (d) an adult with an iron
10. 10.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) plugging in the iron (c) putting the iron away (d) ironing the paper
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the iron setting (c) the ironing time (d) how dark the writing is
12. 12.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
13. 13.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
14. 14.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
15. 15.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
16. 16.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if shaken (d) yes, if cooled
17. 17.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
18. 18.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
19. 19.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
20. 20.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
22. 22.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
24. 24.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
25. 25.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) paper turns lemony (d) the juice scorches first
26. 26.True or false: reading the message is a job for an adult. (a) False (b) True
27. 27.True or false: cutting the lemon is a job a child can do. (a) False (b) True
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) how dark the writing is (c) the kind of juice
29. 29.True or false: plugging in the iron is a job for an adult. (a) False (b) True
30. 30.True or false: putting the iron away is a job for an adult. (a) False (b) True
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) a cotton bud (d) yeast
32. 32.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) plugging in the iron (d) letting the paper dry
33. 33.⚖️ 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 keep it the same (c) we change it
34. 34.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
36. 36.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) putting the iron away (d) dipping the cotton bud
37. 37.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) lemon juice (d) yeast
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) a small bowl (c) white paper (d) an adult with an iron
39. 39.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) a cotton bud (d) yeast
40. 40.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed

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