Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 639 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a magnet (c) an adult with an iron (d) a cotton bud
2. 2.⚖️ 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
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a battery cell (c) lemon juice (d) an adult with an iron
5. 5.🛟 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
6. 6.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
7. 7.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
8. 8.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
9. 9.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) plugging in the iron
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
11. 11.True or false: plugging in the iron is a job a child can do. (a) True (b) False
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
13. 13.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
14. 14.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
15. 15.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
16. 16.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) putting the iron away (d) reading the message
17. 17.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) putting the iron away (d) dipping the cotton bud
18. 18.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) writing the message
19. 19.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
20. 20.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) white paper (c) a battery cell (d) turmeric powder
21. 21.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
22. 22.True or false: writing the message is a job a child can do. (a) False (b) True
23. 23.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) a mirror (d) a small bowl
24. 24.True or false: yeast is needed for the secret lemon message. (a) True (b) False
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) lemon juice (c) a cotton bud (d) white paper
26. 26.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
27. 27.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) almost nothing (d) dark brown words
28. 28.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
29. 29.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
30. 30.True or false: ironing the paper is a job for an adult. (a) True (b) False
31. 31.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) cutting the lemon
32. 32.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same cotton bud (c) the iron setting (d) the same paper
34. 34.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
35. 35.⚖️ 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) how dark the writing is (d) the ironing time
36. 36.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) reading the message (c) plugging in the iron (d) cutting the lemon
37. 37.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
38. 38.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
39. 39.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
40. 40.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) cutting the lemon (d) plugging in the iron

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