Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 504 · 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.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
2. 2.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
3. 3.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
4. 4.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
5. 5.🛟 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
6. 6.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
7. 7.⚖️ 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
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
9. 9.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
10. 10.🍋 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
11. 11.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
12. 12.⚖️ 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
13. 13.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) wash your hands (d) rub your eyes
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
15. 15.True or false: putting the iron away is a job a child can do. (a) False (b) True
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
17. 17.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the same cotton bud (c) the kind of juice (d) how dark the writing is
19. 19.🍋 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) cutting the lemon
20. 20.⚖️ 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
21. 21.⚖️ 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
22. 22.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) plugging in the iron (c) writing the message (d) dipping the cotton bud
23. 23.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
24. 24.⚖️ 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 measure it (c) we keep it the same
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) lemon juice (d) turmeric powder
26. 26.True or false: plugging in the iron is a job for an adult. (a) False (b) True
27. 27.⚖️ 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 cotton bud (c) the kind of juice
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) white paper (d) a magnet
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) yeast (d) white paper
30. 30.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
31. 31.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
32. 32.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
33. 33.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
34. 34.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if cooled (d) yes, if shaken
35. 35.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
36. 36.True or false: ironing the paper is a job a child can do. (a) True (b) False
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
38. 38.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) ironing the paper (d) plugging in the iron
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) a cotton bud (c) a small bowl (d) lemon juice
40. 40.True or false: yeast is not needed for the secret lemon message. (a) True (b) False

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