Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 581 · 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.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) dark brown words (d) blue words
2. 2.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
3. 3.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
4. 4.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) writing turns green (d) it gets darker
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a battery cell (d) an adult with an iron
6. 6.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) ironing the paper (d) letting the paper dry
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
8. 8.⚖️ 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 ironing time (c) the iron setting (d) how dark the writing is
9. 9.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
10. 10.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) whoever is fastest (d) any child
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a mirror (c) a balloon (d) a battery cell
12. 12.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
13. 13.⚖️ 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
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) white paper (d) yeast
15. 15.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
16. 16.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
17. 17.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
18. 18.True or false: plugging in the iron is a job a child can do. (a) False (b) True
19. 19.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) plugging in the iron
20. 20.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) letting the paper dry
21. 21.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) reading the message (c) putting the iron away (d) ironing the paper
22. 22.True or false: writing the message is a job a child can do. (a) False (b) True
23. 23.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
24. 24.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the kind of juice (c) how dark the writing is (d) the same cotton bud
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) white paper (d) a balloon
28. 28.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) dipping the cotton bud (d) writing the message
29. 29.True or false: putting the iron away is a job a child can do. (a) True (b) False
30. 30.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a mirror (c) turmeric powder (d) a balloon
31. 31.🔮 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
32. 32.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) dipping the cotton bud
33. 33.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) writing the message (d) putting the iron away
34. 34.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) reading the message (d) putting the iron away
35. 35.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) wash your hands (d) skip washing
36. 36.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) writing the message (d) letting the paper dry
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
38. 38.⚖️ 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 change it (c) we measure it
39. 39.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a magnet (c) yeast (d) a balloon
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a small bowl (d) a magnet

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