Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 761 · 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? True or false: the ironing time is kept the same. (a) True (b) False
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 what we measure? (a) how dark the writing is (b) the same paper (c) the ironing time (d) the kind of juice
4. 4.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a mirror (c) turmeric powder (d) yeast
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) lemon juice (d) yeast
6. 6.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
7. 7.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
8. 8.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
9. 9.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
10. 10.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
11. 11.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the paper ate it (c) the ink is magnetic (d) it turned into air
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 keep it the same (b) we measure it (c) we change it
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) a cotton bud (d) lemon juice
15. 15.True or false: writing the message is a job for an adult. (a) False (b) True
16. 16.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) a small bowl (d) white paper
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.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) a battery cell (d) yeast
20. 20.True or false: cutting the lemon is a job a child can do. (a) True (b) False
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) lemon juice (c) a small bowl (d) a cotton bud
22. 22.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
23. 23.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) dipping the cotton bud (d) ironing the paper
24. 24.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
25. 25.🍋 Which of these steps is a job a child can do? (a) reading the message (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
26. 26.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) paper turns lemony (d) heat adds colour
27. 27.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) reading the message (d) writing the message
28. 28.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) ironing the paper (d) letting the paper dry
29. 29.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
30. 30.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) chemical (d) musical
31. 31.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
32. 32.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) putting the iron away (d) writing the message
33. 33.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) it gets darker (d) writing turns green
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) white paper (d) a battery cell
35. 35.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
36. 36.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
37. 37.True or false: white paper is needed for the secret lemon message. (a) False (b) True
38. 38.True or false: plugging in the iron is a job a child can do. (a) False (b) True
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
40. 40.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed

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