Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 359 · 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.🔮 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
2. 2.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) plugging in the iron (c) letting the paper dry (d) writing the message
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) yeast (d) lemon juice
4. 4.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) rub your eyes (d) lick your fingers
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a mirror (d) a small bowl
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the ironing time (c) the same cotton bud (d) the kind of juice
7. 7.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
8. 8.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) dipping the cotton bud
9. 9.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) plugging in the iron (d) letting the paper dry
10. 10.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
11. 11.⚖️ 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) the same paper (c) how dark the writing is
12. 12.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
13. 13.True or false: ironing the paper is a job a child can do. (a) False (b) True
14. 14.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
15. 15.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
16. 16.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
17. 17.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
18. 18.⚖️ 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 measure it (c) we keep it the same
19. 19.⚖️ 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
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) a cotton bud (d) an adult with an iron
21. 21.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it can burn skin (d) it is cold
22. 22.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) brown (d) green
23. 23.True or false: yeast is needed for the secret lemon message. (a) False (b) True
24. 24.True or false: white paper is needed for the secret lemon message. (a) True (b) False
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) turmeric powder (d) an adult with an iron
26. 26.⚖️ 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
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
28. 28.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
29. 29.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
30. 30.⚖️ 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) False (b) True
31. 31.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) a battery cell (d) lemon juice
33. 33.⚖️ 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
34. 34.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
35. 35.⚖️ 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 measure it (c) we change it
36. 36.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same paper (c) the iron setting (d) how dark the writing is
38. 38.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) heat adds colour (d) paper turns lemony
39. 39.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a magnet (d) a small bowl

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