Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 899 · 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.⚖️ 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
2. 2.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a balloon (c) a small bowl (d) a cotton bud
4. 4.True or false: cutting the lemon is a job for an adult. (a) True (b) False
5. 5.True or false: ironing the paper is a job for an adult. (a) False (b) True
6. 6.⚖️ 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 keep it the same (c) we change it
7. 7.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) a cotton bud (c) white paper (d) lemon juice
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) lemon juice (d) white paper
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) yeast (d) white paper
11. 11.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
12. 12.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a cotton bud (d) turmeric powder
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a small bowl (d) a mirror
15. 15.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
17. 17.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
18. 18.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) plugging in the iron (d) writing the message
19. 19.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
20. 20.⚖️ 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 keep it the same (c) we measure it
21. 21.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) writing the message (d) putting the iron away
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
23. 23.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) heat adds colour (d) paper turns lemony
24. 24.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is cold (d) it is magnetic
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) lemon juice (d) a magnet
26. 26.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
27. 27.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
28. 28.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
29. 29.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) turmeric powder (d) a small bowl
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
31. 31.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
32. 32.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) reading the message (d) plugging in the iron
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the same cotton bud (c) the kind of juice (d) the iron setting
34. 34.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
35. 35.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
36. 36.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
38. 38.⚖️ 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
39. 39.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) letting the paper dry (c) writing the message (d) reading the message
40. 40.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) an adult with an iron (d) a battery cell

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