Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 897 · 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? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
2. 2.⚖️ 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) how dark the writing is (c) the iron setting (d) the kind of juice
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
4. 4.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) reading the message
5. 5.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
6. 6.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
7. 7.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
8. 8.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
9. 9.True or false: letting the paper dry is a job for an adult. (a) False (b) True
10. 10.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
12. 12.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
13. 13.True or false: ironing the paper is a job a child can do. (a) False (b) True
14. 14.⚖️ 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 paper
15. 15.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) cutting the lemon (d) letting the paper dry
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
17. 17.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
18. 18.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) turmeric powder (d) white paper
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
21. 21.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
22. 22.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
23. 23.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a cotton bud (d) a magnet
24. 24.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
25. 25.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
26. 26.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
27. 27.🍋 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) plugging in the iron
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) an adult with an iron (d) a cotton bud
29. 29.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) a battery cell (d) an adult with an iron
31. 31.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
32. 32.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) letting the paper dry
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
34. 34.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) reading the message
35. 35.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
36. 36.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) white paper (d) yeast
38. 38.⚖️ 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 change it (c) we keep it the same
39. 39.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it

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