Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 724 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
2. 2.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) plugging in the iron (c) writing the message (d) dipping the cotton bud
3. 3.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) letting the paper dry (d) plugging in the iron
4. 4.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) writing the message (d) plugging in the iron
5. 5.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) a magnet (d) turmeric powder
6. 6.True or false: letting the paper dry is a job for an adult. (a) True (b) False
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) an adult with an iron
10. 10.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) lemon juice (c) a small bowl (d) an adult with an iron
12. 12.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a balloon (d) a small bowl
14. 14.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) yeast (d) a balloon
16. 16.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) lemon juice (d) a cotton bud
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) the kind of juice (c) how dark the writing is
19. 19.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) paper turns lemony (d) the iron is brown
20. 20.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
21. 21.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
23. 23.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
24. 24.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
25. 25.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
26. 26.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
27. 27.⚖️ 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 same paper (c) the same cotton bud (d) how dark the writing is
28. 28.🔍 Which is the odd one out? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
29. 29.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) reading the message (d) writing the message
30. 30.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) writing the message (d) ironing the paper
31. 31.⚖️ 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 keep it the same (c) we change it
32. 32.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
33. 33.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) dipping the cotton bud
34. 34.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
35. 35.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
36. 36.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
37. 37.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
38. 38.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) blue words (d) almost nothing
39. 39.⚖️ 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 change it (c) we measure it
40. 40.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed

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