Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 403 · 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.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) dipping the cotton bud (d) ironing the paper
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
3. 3.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
4. 4.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the kind of juice (c) the same paper (d) the same cotton bud
6. 6.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) skip washing (d) lick your fingers
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) an adult with an iron (c) a cotton bud (d) lemon juice
8. 8.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) reading the message (d) dipping the cotton bud
9. 9.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
10. 10.⚖️ 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
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) an adult with an iron (c) a cotton bud (d) lemon juice
12. 12.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
13. 13.⚖️ 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
14. 14.⚖️ 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 cotton bud (c) how dark the writing is
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the same cotton bud (d) the ironing time
16. 16.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) a battery cell (d) a mirror
17. 17.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) brown (d) green
19. 19.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
20. 20.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a battery cell (c) yeast (d) turmeric powder
22. 22.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) putting the iron away
23. 23.🔍 Which is the odd one out? (a) letting the paper dry (b) cutting the lemon (c) reading the message (d) dipping the cotton bud
24. 24.🔮 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
25. 25.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
26. 26.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) letting the paper dry
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
28. 28.True or false: plugging in the iron is a job for an adult. (a) False (b) True
29. 29.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) letting the paper dry (c) ironing the paper (d) cutting the lemon
30. 30.True or false: writing the message is a job for an adult. (a) True (b) False
31. 31.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
32. 32.⚖️ 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
33. 33.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a cotton bud (d) turmeric powder
35. 35.⚖️ 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 measure it (c) we change it
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) white paper (d) a cotton bud
37. 37.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
38. 38.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a balloon (c) turmeric powder (d) a magnet
39. 39.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) yeast (c) an adult with an iron (d) lemon juice

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