Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 393 · 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) dipping the cotton bud (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) lemon juice
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a cotton bud (d) a battery cell
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) lemon juice (d) white paper
5. 5.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
6. 6.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) dipping the cotton bud (c) reading the message (d) writing the message
7. 7.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) magnetic (d) musical
8. 8.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
9. 9.True or false: white paper is needed for the secret lemon message. (a) False (b) True
10. 10.🍋 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
11. 11.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) plugging in the iron (d) dipping the cotton bud
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a balloon (c) an adult with an iron (d) a cotton bud
14. 14.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
15. 15.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) ironing the paper (d) reading the message
16. 16.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is sticky (d) it is cold
17. 17.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
19. 19.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) a mirror (d) white paper
20. 20.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, if shaken (d) yes, in the dark
21. 21.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
22. 22.⚖️ 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) how dark the writing is (c) the ironing time
23. 23.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same cotton bud (c) how dark the writing is (d) the iron setting
25. 25.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
26. 26.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) rub your eyes (d) skip washing
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) an adult with an iron (d) white paper
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) any child (d) only an adult
29. 29.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
30. 30.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
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 iron setting (c) the kind of juice (d) the same paper
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
34. 34.🍋 Which of these steps is a job a child can do? (a) reading the message (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
35. 35.True or false: plugging in the iron is a job for an adult. (a) True (b) False
36. 36.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
37. 37.True or false: writing the message is a job for an adult. (a) True (b) False
38. 38.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
40. 40.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) letting the paper dry

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