Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 651 · 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.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
2. 2.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
3. 3.⚖️ 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) the same paper (d) how dark the writing is
4. 4.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) turmeric powder (b) an adult with an iron (c) a cotton bud (d) a small bowl
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a small bowl (c) a balloon (d) yeast
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) a balloon (d) a cotton bud
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
11. 11.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is cold (d) it is sticky
12. 12.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) yeast (c) a battery cell (d) white paper
13. 13.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
14. 14.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) physical (d) magnetic
15. 15.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) it gets darker (d) the paper floats
16. 16.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
17. 17.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a battery cell (d) white paper
18. 18.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, if cooled (d) yes, in the dark
19. 19.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) cutting the lemon
20. 20.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
21. 21.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) writing the message (d) putting the iron away
22. 22.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) cutting the lemon
23. 23.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
24. 24.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
25. 25.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
26. 26.True or false: reading the message is a job for an adult. (a) False (b) True
27. 27.True or false: writing the message is a job for an adult. (a) True (b) False
28. 28.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
29. 29.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) plugging in the iron (d) reading the message
30. 30.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
31. 31.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
32. 32.True or false: cutting the lemon is a job for an adult. (a) True (b) False
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a cotton bud (d) yeast
34. 34.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) ironing the paper
35. 35.⚖️ 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 same paper
36. 36.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) white paper (d) a mirror
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) an adult with an iron (c) a small bowl (d) white paper
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a magnet (c) white paper (d) a cotton bud
40. 40.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony

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