Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 3 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) a cotton bud (c) white paper (d) an adult with an iron
2. 2.🛟 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
3. 3.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
4. 4.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) writing the message (d) plugging in the iron
5. 5.⚖️ 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
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
7. 7.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
8. 8.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
9. 9.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) reading the message (d) plugging in the iron
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
11. 11.🛟 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
12. 12.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a battery cell (c) a magnet (d) yeast
13. 13.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) writing the message
14. 14.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
15. 15.⚖️ 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
16. 16.🔮 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
17. 17.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) an adult with an iron (d) a mirror
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the same paper (c) how dark the writing is (d) the ironing time
19. 19.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) chemical (d) magnetic
20. 20.🧺 Do we need yeast 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) False (b) True
22. 22.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) reading the message (d) ironing the paper
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
24. 24.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
25. 25.True or false: letting the paper dry is a job a child can do. (a) False (b) True
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
27. 27.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) turmeric powder (c) a cotton bud (d) lemon juice
29. 29.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) wash your hands (d) lick your fingers
30. 30.True or false: putting the iron away is a job a child can do. (a) True (b) False
31. 31.True or false: putting the iron away is a job for an adult. (a) True (b) False
32. 32.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
33. 33.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
34. 34.🍋 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
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) white paper (d) lemon juice
36. 36.🍋 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) cutting the lemon
37. 37.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a balloon (d) white paper
38. 38.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
39. 39.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
40. 40.⚖️ 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

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