Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 417 · 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 steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) letting the paper dry (d) cutting the lemon
2. 2.⚖️ 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 same cotton bud (c) the kind of juice
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) lemon juice (c) white paper (d) a cotton bud
4. 4.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) heat adds colour (d) paper turns lemony
6. 6.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
7. 7.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
9. 9.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
10. 10.True or false: ironing the paper is a job for an adult. (a) True (b) False
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
12. 12.⚖️ 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
13. 13.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
14. 14.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
15. 15.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
16. 16.⚖️ 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 ironing time (c) the kind of juice
17. 17.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) dipping the cotton bud
18. 18.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) letting the paper dry (d) dipping the cotton bud
19. 19.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
20. 20.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
21. 21.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) an adult with an iron (d) a battery cell
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) a mirror (d) white paper
24. 24.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) writing the message (d) dipping the cotton bud
25. 25.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
26. 26.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
27. 27.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) putting the iron away
28. 28.True or false: ironing the paper is a job a child can do. (a) True (b) False
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
30. 30.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
31. 31.⚖️ 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
32. 32.🧺 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) a battery cell
33. 33.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
34. 34.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) writing the message
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) True (b) False
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the ironing time (c) the kind of juice (d) the same paper
37. 37.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
38. 38.True or false: plugging in the iron is a job a child can do. (a) True (b) False
39. 39.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
40. 40.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) ironing the paper

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