Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 753 · 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 measure it (b) we keep it the same (c) we change it
2. 2.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
3. 3.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) writing the message (d) reading the message
4. 4.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) letting the paper dry
5. 5.🔍 Which is the odd one out? (a) cutting the lemon (b) reading the message (c) letting the paper dry (d) writing the message
6. 6.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing turns green (d) writing stays faint
8. 8.True or false: plugging in the iron is a job a child can do. (a) True (b) False
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) yeast (c) a small bowl (d) a cotton bud
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) turmeric powder (d) a cotton bud
11. 11.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
12. 12.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
13. 13.True or false: plugging in the iron is a job for an adult. (a) False (b) True
14. 14.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) it turned into air (d) the paper ate it
16. 16.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) a magnet (d) an adult with an iron
17. 17.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it can burn skin (d) it is cold
18. 18.True or false: reading the message is a job for an adult. (a) False (b) True
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a magnet (c) white paper (d) a small bowl
20. 20.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) reading the message (d) plugging in the iron
21. 21.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) dipping the cotton bud
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the same cotton bud (c) how dark the writing is (d) the ironing time
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) True (b) False
24. 24.🍋 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
25. 25.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
26. 26.⚖️ 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
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a balloon (d) white paper
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) turmeric powder (d) white paper
29. 29.True or false: letting the paper dry is a job for an adult. (a) False (b) True
30. 30.True or false: white paper is needed for the secret lemon message. (a) True (b) False
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.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a cotton bud (d) a magnet
34. 34.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
35. 35.⚖️ 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
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
37. 37.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
38. 38.⚖️ 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
39. 39.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) lemon juice (d) a mirror
40. 40.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical

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