Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 128 · 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) a cotton bud (b) lemon juice (c) white paper (d) yeast
2. 2.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) an adult with an iron (d) a mirror
4. 4.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
5. 5.🔍 Which is the odd one out? (a) letting the paper dry (b) cutting the lemon (c) putting the iron away (d) ironing the paper
6. 6.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) a rainbow (d) blue words
7. 7.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) cutting the lemon (d) writing the message
8. 8.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) only an adult (d) the youngest child
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) lemon juice (c) white paper (d) a small bowl
10. 10.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
11. 11.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
12. 12.True or false: letting the paper dry is a job for an adult. (a) True (b) False
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
14. 14.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the iron setting (c) the kind of juice (d) the same paper
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a cotton bud (c) turmeric powder (d) a balloon
17. 17.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
18. 18.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
19. 19.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) a magnet (d) lemon juice
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud
22. 22.⚖️ 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
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) yeast (c) a small bowl (d) lemon juice
24. 24.⚖️ 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
25. 25.True or false: putting the iron away is a job a child can do. (a) False (b) True
26. 26.True or false: ironing the paper is a job for an adult. (a) False (b) True
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
28. 28.True or false: writing the message is a job a child can do. (a) False (b) True
29. 29.⚖️ 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 ironing time (c) the kind of juice (d) the iron setting
30. 30.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) putting the iron away (d) letting the paper dry
31. 31.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
32. 32.🧺 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) a magnet
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) white paper (c) a cotton bud (d) lemon juice
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.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
37. 37.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
38. 38.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a cotton bud (d) a balloon
40. 40.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony

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