Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 829 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a magnet (d) a small bowl
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) a small bowl (d) white paper
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
4. 4.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the juice scorches first (d) the iron is brown
5. 5.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
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.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
8. 8.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) turmeric powder (d) a cotton bud
9. 9.⚖️ 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
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
11. 11.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
13. 13.🧺 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 balloon
14. 14.⚖️ 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
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) lemon juice (d) white paper
16. 16.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
18. 18.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) yeast (d) a small bowl
20. 20.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
21. 21.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) reading the message
22. 22.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a small bowl (c) white paper (d) lemon juice
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
25. 25.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) a cotton bud (c) lemon juice (d) a small bowl
27. 27.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
28. 28.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
29. 29.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) letting the paper dry
30. 30.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) dipping the cotton bud (c) putting the iron away (d) ironing the paper
31. 31.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a mirror (c) a battery cell (d) a magnet
33. 33.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
34. 34.⚖️ 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 kind of juice (c) the ironing time (d) the iron setting
35. 35.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
36. 36.True or false: reading the message is a job a child can do. (a) False (b) True
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) lemon juice (d) white paper
38. 38.True or false: ironing the paper is a job a child can do. (a) False (b) True
39. 39.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) yes, if shaken (d) no, it stays brown
40. 40.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed

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