Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 8 · 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: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) the paper floats (d) writing turns green
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the ironing time (c) the same cotton bud (d) how dark the writing is
3. 3.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
4. 4.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) almost nothing (d) blue words
5. 5.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) cutting the lemon (d) reading the message
6. 6.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) letting the paper dry (c) reading the message (d) dipping the cotton bud
7. 7.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green
9. 9.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) a cotton bud (d) a magnet
11. 11.True or false: plugging in the iron is a job for an adult. (a) True (b) False
12. 12.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
13. 13.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
14. 14.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
15. 15.🧺 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 battery cell
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a cotton bud (d) a mirror
17. 17.🍋 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
18. 18.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) turmeric powder (c) a balloon (d) a battery cell
19. 19.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
20. 20.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
21. 21.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
22. 22.🍋 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
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
24. 24.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) ironing the paper
25. 25.True or false: white paper is needed for the secret lemon message. (a) False (b) True
26. 26.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) how dark the writing is (c) the kind of juice
28. 28.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) ironing the paper (d) writing the message
29. 29.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) putting the iron away (d) plugging in the iron
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
31. 31.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
32. 32.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
33. 33.⚖️ 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 keep it the same (c) we change it
34. 34.⚖️ 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
35. 35.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) plugging in the iron (d) writing the message
36. 36.⚖️ 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 kind of juice (c) the ironing time (d) the same paper
37. 37.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
39. 39.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
40. 40.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) dipping the cotton bud

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