Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 654 · 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 not needed for the secret lemon message? (a) a balloon (b) white paper (c) a small bowl (d) lemon juice
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
4. 4.⚖️ 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 same paper (c) the same cotton bud (d) the kind of juice
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) only an adult (d) the youngest child
6. 6.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
7. 7.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
8. 8.True or false: reading the message is a job for an adult. (a) False (b) True
9. 9.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
10. 10.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
11. 11.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
12. 12.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
13. 13.⚖️ 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
14. 14.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) yeast (c) an adult with an iron (d) lemon juice
17. 17.⚖️ 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
18. 18.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
19. 19.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the kind of juice (c) the iron setting (d) how dark the writing is
21. 21.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
22. 22.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
23. 23.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
24. 24.⚖️ 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 change it (c) we measure it
25. 25.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a mirror (c) an adult with an iron (d) a small bowl
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) dry juice is see-through (d) it turned into air
28. 28.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
29. 29.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) letting the paper dry (d) putting the iron away
30. 30.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) white paper (d) a cotton bud
32. 32.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) writing the message (c) reading the message (d) letting the paper dry
33. 33.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
35. 35.True or false: letting the paper dry is a job a child can do. (a) False (b) True
36. 36.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) dipping the cotton bud (d) plugging in the iron
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
38. 38.True or false: ironing the paper is a job a child can do. (a) True (b) False
39. 39.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) ironing the paper (d) plugging in the iron
40. 40.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) writing the message (d) reading the message

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