Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 411 · 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.True or false: putting the iron away is a job a child can do. (a) False (b) True
2. 2.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) ironing the paper (d) putting the iron away
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
4. 4.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
5. 5.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
6. 6.True or false: plugging in the iron is a job a child can do. (a) False (b) True
7. 7.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the iron setting
9. 9.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) reading the message
10. 10.⚖️ 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) how dark the writing is (d) the iron setting
11. 11.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
13. 13.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) letting the paper dry (d) ironing the paper
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
15. 15.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
16. 16.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) a rainbow (d) blue words
17. 17.⚖️ 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
18. 18.🧺 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 balloon (d) white paper
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) white paper (d) yeast
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) an adult with an iron (c) lemon juice (d) a cotton bud
21. 21.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) white (d) green
22. 22.⚖️ 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
23. 23.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) a small bowl (d) lemon juice
25. 25.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) it turned into air (d) dry juice is see-through
26. 26.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) the paper floats (d) writing turns green
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) lemon juice (d) white paper
28. 28.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
29. 29.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
30. 30.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) yeast (c) lemon juice (d) a cotton bud
32. 32.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) reading the message
33. 33.⚖️ 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
34. 34.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a magnet (c) a mirror (d) a battery cell
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) turmeric powder (c) an adult with an iron (d) a cotton bud
37. 37.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) plugging in the iron (d) letting the paper dry
38. 38.⚖️ 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
39. 39.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
40. 40.True or false: yeast is needed for the secret lemon message. (a) True (b) False

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