Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 256 · 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 — cutting the lemon? (a) a child can do it (b) an adult does it
2. 2.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
3. 3.⚖️ 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
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) lemon juice (d) a battery cell
5. 5.True or false: plugging in the iron is a job for an adult. (a) False (b) True
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) a mirror (d) yeast
7. 7.True or false: reading the message is a job a child can do. (a) False (b) True
8. 8.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
9. 9.🍋 Which of these steps is a job a child can do? (a) reading the message (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a balloon (d) an adult with an iron
11. 11.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
12. 12.True or false: putting the iron away is a job for an adult. (a) True (b) False
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) a cotton bud (d) turmeric powder
14. 14.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
16. 16.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) putting the iron away (d) ironing the paper
17. 17.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
18. 18.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) lemon juice (d) an adult with an iron
20. 20.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
21. 21.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
22. 22.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) white paper (c) a small bowl (d) lemon juice
24. 24.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) writing the message
25. 25.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
26. 26.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
27. 27.🍋 Which of these steps is a job for an adult? (a) reading the message (b) putting the iron away (c) letting the paper dry (d) writing the message
28. 28.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
29. 29.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) letting the paper dry (d) cutting the lemon
30. 30.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
31. 31.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
33. 33.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) rub your eyes (d) skip washing
34. 34.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) writing the message (d) ironing the paper
35. 35.🔍 Which is the odd one out? (a) putting the iron away (b) letting the paper dry (c) plugging in the iron (d) cutting the lemon
36. 36.⚖️ 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 measure it (c) we keep it the same
37. 37.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
38. 38.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) yeast (d) a cotton bud
39. 39.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
40. 40.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False

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