Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 95 · 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? Which of these is kept the same? (a) how dark the writing is (b) the ironing time (c) the kind of juice
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
3. 3.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a mirror (d) a small bowl
7. 7.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) writing the message (d) dipping the cotton bud
8. 8.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) writing the message
9. 9.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) turmeric powder (d) a cotton bud
11. 11.⚖️ 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
12. 12.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
13. 13.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) cutting the lemon (d) putting the iron away
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the iron setting (c) the same paper (d) how dark the writing is
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a balloon (d) white paper
16. 16.True or false: writing the message is a job a child can do. (a) False (b) True
17. 17.⚖️ 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 kind of juice (c) the same cotton bud
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
19. 19.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
20. 20.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
21. 21.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
22. 22.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) magnetic (d) chemical
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
24. 24.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) dipping the cotton bud
25. 25.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
26. 26.🍋 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
27. 27.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) reading the message (d) letting the paper dry
28. 28.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) a cotton bud (d) a small bowl
30. 30.⚖️ 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
31. 31.🍋 Which of these steps is a job for an adult? (a) writing the message (b) putting the iron away (c) letting the paper dry (d) reading the message
32. 32.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
33. 33.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) lemon juice (d) turmeric powder
35. 35.True or false: letting the paper dry is a job for an adult. (a) True (b) False
36. 36.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we keep it the same (c) we change it
38. 38.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) a battery cell (d) a balloon
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a battery cell (c) an adult with an iron (d) lemon juice
40. 40.⚖️ 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 same cotton bud (c) the kind of juice (d) how dark the writing is

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