Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 699 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
2. 2.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
3. 3.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
4. 4.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) yeast (d) a small bowl
5. 5.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) putting the iron away (d) writing the message
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.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
8. 8.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
9. 9.🧺 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) white paper (d) a battery cell
10. 10.⚖️ 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
11. 11.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
12. 12.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) ironing the paper (d) reading the message
13. 13.⚖️ 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
14. 14.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
15. 15.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
16. 16.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
17. 17.🧺 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 magnet (d) lemon juice
18. 18.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) dry juice is see-through (d) the paper ate it
19. 19.⚖️ 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
20. 20.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
21. 21.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
22. 22.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) letting the paper dry (d) reading the message
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
24. 24.True or false: plugging in the iron is a job a child can do. (a) False (b) True
25. 25.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) a balloon (d) lemon juice
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
28. 28.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
29. 29.⚖️ 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) True (b) False
30. 30.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) dark brown words (d) a rainbow
31. 31.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
32. 32.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if cooled (d) yes, if shaken
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
34. 34.⚖️ 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 same cotton bud (c) the kind of juice (d) the same paper
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) white paper (d) yeast
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the same paper (c) how dark the writing is
37. 37.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) cutting the lemon (d) letting the paper dry
38. 38.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) plugging in the iron (d) putting the iron away
39. 39.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) reading the message
40. 40.⚖️ 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

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