Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 335 · 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) blue words (b) a rainbow (c) dark brown words (d) almost nothing
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
3. 3.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) ironing the paper (d) dipping the cotton bud
4. 4.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
5. 5.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
6. 6.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) dipping the cotton bud (d) putting the iron away
7. 7.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a battery cell (d) lemon juice
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a magnet (c) turmeric powder (d) a balloon
10. 10.⚖️ 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 iron setting
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
12. 12.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
13. 13.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
14. 14.⚖️ 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) True (b) False
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) a magnet (d) a cotton bud
17. 17.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
18. 18.⚖️ 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
19. 19.True or false: white paper is needed for the secret lemon message. (a) True (b) False
20. 20.True or false: writing the message is a job a child can do. (a) False (b) True
21. 21.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
22. 22.🧺 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
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) a battery cell (d) lemon juice
24. 24.⚖️ 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
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
26. 26.🔍 Which is the odd one out? (a) writing the message (b) putting the iron away (c) letting the paper dry (d) dipping the cotton bud
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) the ink is magnetic (d) it turned into air
28. 28.True or false: letting the paper dry is a job for an adult. (a) False (b) True
29. 29.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) cutting the lemon (d) writing the message
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same paper (c) the iron setting (d) the kind of juice
31. 31.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) a small bowl (c) lemon juice (d) an adult with an iron
33. 33.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
34. 34.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
35. 35.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) reading the message (d) putting the iron away
36. 36.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a balloon (d) a small bowl
37. 37.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
38. 38.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
39. 39.🔮 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
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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