Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 449 · 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.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
2. 2.🧺 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) yeast (d) white paper
3. 3.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
4. 4.⚖️ 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) True (b) False
5. 5.⚖️ 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
6. 6.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) whoever is fastest (d) any child
7. 7.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) cutting the lemon (d) plugging in the iron
8. 8.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) dipping the cotton bud (d) plugging in the iron
9. 9.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
10. 10.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) rub your eyes (d) lick your fingers
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a magnet (d) a small bowl
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) yeast (d) lemon juice
14. 14.🔮 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
15. 15.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
16. 16.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) putting the iron away (d) reading the message
17. 17.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) cutting the lemon
18. 18.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
19. 19.⚖️ 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 same paper
20. 20.True or false: cutting the lemon is a job for an adult. (a) False (b) True
21. 21.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
22. 22.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
24. 24.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, if cooled (d) yes, in the dark
25. 25.⚖️ 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 change it (c) we keep it the same
26. 26.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) a small bowl (c) lemon juice (d) an adult with an iron
29. 29.⚖️ 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
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) lemon juice (c) an adult with an iron (d) a small bowl
31. 31.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
32. 32.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) a rainbow (d) blue words
33. 33.⚖️ 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 iron setting (c) how dark the writing is
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) white paper (d) yeast
35. 35.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
36. 36.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) dipping the cotton bud (d) writing the message
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) white paper (d) a balloon
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a battery cell (d) a cotton bud
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) a small bowl (d) an adult with an iron

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