Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 240 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
2. 2.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
3. 3.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
4. 4.⚖️ 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
5. 5.True or false: writing the message is a job for an adult. (a) False (b) True
6. 6.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) ironing the paper
7. 7.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) white paper (c) a small bowl (d) lemon juice
9. 9.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) letting the paper dry (d) dipping the cotton bud
10. 10.⚖️ 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
11. 11.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
12. 12.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) turmeric powder (d) a cotton bud
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the kind of juice (c) the ironing time (d) the same paper
15. 15.True or false: cutting the lemon is a job a child can do. (a) True (b) False
16. 16.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) writing the message (d) letting the paper dry
17. 17.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) putting the iron away (d) ironing the paper
18. 18.⚖️ 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
19. 19.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
20. 20.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
21. 21.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
22. 22.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) reading the message
23. 23.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, in the dark (d) yes, if shaken
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
25. 25.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
26. 26.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
28. 28.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
29. 29.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
30. 30.⚖️ 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
31. 31.⚖️ 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
32. 32.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
34. 34.🍋 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
35. 35.True or false: putting the iron away is a job a child can do. (a) True (b) False
36. 36.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a battery cell (d) white paper
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) lemon juice (d) a cotton bud
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
40. 40.🍋 Which of these steps is a job a child can do? (a) writing the message (b) putting the iron away (c) ironing the paper (d) plugging in the iron

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