Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 767 · 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.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) yeast (c) a balloon (d) a magnet
2. 2.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
3. 3.⚖️ 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 same paper (c) the kind of juice
4. 4.True or false: reading the message is a job for an adult. (a) True (b) False
5. 5.⚖️ 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) True (b) False
6. 6.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) reading the message
7. 7.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
8. 8.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
9. 9.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) lick your fingers (d) wash your hands
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
11. 11.True or false: reading the message is a job a child can do. (a) False (b) True
12. 12.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) a mirror (d) a battery cell
13. 13.⚖️ 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 cotton bud (c) the same paper (d) the kind of juice
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
15. 15.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the juice scorches first (d) the iron is brown
16. 16.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) writing the message (c) cutting the lemon (d) plugging in the iron
17. 17.⚖️ 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) how dark the writing is (c) the iron setting (d) the same paper
18. 18.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
19. 19.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
20. 20.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
21. 21.🧺 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) a cotton bud
22. 22.True or false: writing the message is a job for an adult. (a) False (b) True
23. 23.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
24. 24.⚖️ 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
25. 25.⚖️ 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
26. 26.⚖️ 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
27. 27.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) plugging in the iron (d) dipping the cotton bud
28. 28.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
29. 29.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) lemon juice (c) a cotton bud (d) a small bowl
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
32. 32.True or false: plugging in the iron is a job for an adult. (a) True (b) False
33. 33.True or false: ironing the paper is a job a child can do. (a) True (b) False
34. 34.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
35. 35.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) plugging in the iron
36. 36.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
37. 37.True or false: ironing the paper is a job for an adult. (a) True (b) False
38. 38.🍋 Which of these steps is a job for an adult? (a) reading the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
39. 39.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) a small bowl (d) a balloon
40. 40.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) letting the paper dry (d) reading the message

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