Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 368 · 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.True or false: plugging in the iron is a job a child can do. (a) True (b) False
2. 2.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is cold (d) it is magnetic
3. 3.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
4. 4.⚖️ 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
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) a magnet (d) a cotton bud
6. 6.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) whoever is fastest (d) any child
7. 7.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) letting the paper dry (d) dipping the cotton bud
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
9. 9.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
10. 10.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
11. 11.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
12. 12.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
13. 13.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) a cotton bud (d) turmeric powder
14. 14.🍋 Which of these steps is a job for an adult? (a) reading the message (b) cutting the lemon (c) letting the paper dry (d) dipping the cotton bud
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
16. 16.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
17. 17.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) letting the paper dry
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) a small bowl (d) turmeric powder
19. 19.🍋 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
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a cotton bud (d) a mirror
21. 21.⚖️ 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 keep it the same (c) we measure it
22. 22.⚖️ 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
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) white paper (d) a battery cell
24. 24.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
25. 25.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) dipping the cotton bud (c) plugging in the iron (d) cutting the lemon
26. 26.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a mirror (c) a magnet (d) lemon juice
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air
28. 28.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
29. 29.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
30. 30.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) reading the message (d) writing the message
31. 31.⚖️ 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 ironing time (c) the same cotton bud (d) the kind of juice
32. 32.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
33. 33.🧺 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) yeast (d) white paper
34. 34.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
35. 35.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
36. 36.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) wash your hands (d) lick your fingers
37. 37.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) putting the iron away (d) cutting the lemon
38. 38.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
39. 39.True or false: putting the iron away is a job for an adult. (a) False (b) True
40. 40.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical

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