Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 170 · 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.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
2. 2.🧺 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) white paper (d) turmeric powder
3. 3.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a magnet
5. 5.🧺 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) a balloon
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
8. 8.⚖️ 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 iron setting (c) the same cotton bud (d) how dark the writing is
9. 9.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
10. 10.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
11. 11.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) whoever is fastest (c) the youngest child (d) any child
12. 12.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) it gets darker (d) the paper floats
13. 13.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
14. 14.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) reading the message
15. 15.⚖️ 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 kind of juice (c) the ironing time (d) the same paper
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we keep it the same (c) we change it
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) lemon juice (d) an adult with an iron
18. 18.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
19. 19.True or false: white paper is needed for the secret lemon message. (a) False (b) True
20. 20.True or false: yeast is needed for the secret lemon message. (a) True (b) False
21. 21.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
22. 22.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) letting the paper dry (d) putting the iron away
23. 23.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a mirror (c) yeast (d) a balloon
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.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
26. 26.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
27. 27.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
28. 28.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
30. 30.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) a battery cell (d) a magnet
32. 32.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
33. 33.True or false: writing the message is a job for an adult. (a) True (b) False
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) yeast (d) a cotton bud
35. 35.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) cutting the lemon (d) writing the message
36. 36.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
37. 37.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
38. 38.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
39. 39.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) white paper (c) lemon juice (d) a small bowl

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