Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 541 · 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.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
2. 2.🧺 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) a small bowl (d) yeast
3. 3.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a balloon (c) white paper (d) lemon juice
6. 6.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) writing the message (c) reading the message (d) letting the paper dry
7. 7.⚖️ 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
8. 8.🧺 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) a mirror (d) a cotton bud
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
10. 10.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
11. 11.⚖️ 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
12. 12.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) whoever is fastest (d) the youngest child
13. 13.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) putting the iron away
14. 14.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) letting the paper dry
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) it turned into air (d) the ink is magnetic
16. 16.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
17. 17.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) the paper floats (d) writing turns green
18. 18.🧺 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) a cotton bud (d) a magnet
19. 19.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
20. 20.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
21. 21.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
22. 22.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
23. 23.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
24. 24.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) letting the paper dry (c) putting the iron away (d) ironing the paper
25. 25.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
26. 26.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
27. 27.True or false: putting the iron away is a job a child can do. (a) False (b) True
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the iron setting (c) the same cotton bud (d) the kind of juice
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the same paper (c) how dark the writing is (d) the iron setting
30. 30.True or false: writing the message is a job a child can do. (a) False (b) True
31. 31.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it is magnetic (d) it can burn skin
32. 32.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
33. 33.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) cutting the lemon
34. 34.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) turmeric powder (c) yeast (d) a magnet
35. 35.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) no, it stays brown (d) yes, if shaken
36. 36.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
38. 38.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) physical (d) magnetic
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) lemon juice (d) a magnet

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