Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 394 · 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 — plugging in the iron? (a) an adult does it (b) a child can do it
2. 2.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
3. 3.🛟 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
4. 4.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
6. 6.⚖️ 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
7. 7.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) putting the iron away
8. 8.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
9. 9.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
10. 10.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) cutting the lemon (d) ironing the paper
11. 11.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
12. 12.True or false: cutting the lemon is a job for an adult. (a) True (b) False
13. 13.True or false: ironing the paper is a job a child can do. (a) False (b) True
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the iron setting (c) how dark the writing is (d) the same paper
15. 15.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a mirror (d) lemon juice
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical
18. 18.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
19. 19.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) letting the paper dry (c) writing the message (d) reading the message
20. 20.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
21. 21.⚖️ 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 ironing time (c) the kind of juice (d) how dark the writing is
22. 22.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
23. 23.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
24. 24.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
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 — putting the iron away? (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: how dark the writing is is kept the same. (a) False (b) True
28. 28.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: plugging in the iron is a job for an adult. (a) True (b) False
30. 30.🧺 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 battery cell (d) lemon juice
31. 31.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) ironing the paper
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) False (b) True
33. 33.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) turmeric powder (d) lemon juice
35. 35.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) dark brown words (d) blue words
36. 36.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) yeast (d) a magnet
38. 38.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
39. 39.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False

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