Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 500 · 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 a balloon for the secret lemon message? (a) needed (b) not needed
2. 2.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
3. 3.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
4. 4.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
5. 5.True or false: white paper is needed for the secret lemon message. (a) False (b) True
6. 6.⚖️ 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 keep it the same (c) we measure it
7. 7.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same cotton bud (c) the iron setting (d) the same paper
9. 9.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) almost nothing (d) dark brown words
10. 10.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) an adult with an iron (d) white paper
12. 12.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) letting the paper dry (d) plugging in the iron
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) a small bowl (d) a magnet
14. 14.⚖️ 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) True (b) False
15. 15.True or false: letting the paper dry is a job for an adult. (a) True (b) False
16. 16.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
17. 17.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
18. 18.True or false: writing the message is a job for an adult. (a) True (b) False
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
20. 20.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
21. 21.⚖️ 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
22. 22.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, in the dark (d) yes, if cooled
23. 23.True or false: letting the paper dry is a job a child can do. (a) True (b) False
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a balloon (d) lemon juice
25. 25.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) ironing the paper
26. 26.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
27. 27.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
28. 28.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) yeast (d) a small bowl
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the kind of juice (c) the ironing time (d) the same cotton bud
30. 30.🍋 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
31. 31.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) whoever is fastest (c) the youngest child (d) any child
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) white paper (c) a small bowl (d) a cotton bud
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) a mirror (d) a battery cell
35. 35.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
36. 36.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
38. 38.🍋 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
39. 39.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) writing the message
40. 40.⚖️ 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

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