Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 871 · 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.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) putting the iron away (d) letting the paper dry
2. 2.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
3. 3.🛟 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
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a balloon (d) a cotton bud
5. 5.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) dry juice is see-through (d) it turned into air
6. 6.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) paper turns lemony (d) heat adds colour
7. 7.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
8. 8.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
9. 9.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) white (d) green
10. 10.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a cotton bud (d) a battery cell
12. 12.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
13. 13.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) a rainbow (d) almost nothing
14. 14.⚖️ 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 keep it the same (c) we measure it
15. 15.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
16. 16.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) how dark the writing is (c) the kind of juice (d) the iron setting
18. 18.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) yeast (c) a battery cell (d) a magnet
19. 19.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) writing the message
20. 20.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) writing the message (c) ironing the paper (d) plugging in the iron
21. 21.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) turmeric powder (c) white paper (d) lemon juice
24. 24.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) any child (c) the youngest child (d) whoever is fastest
25. 25.🧺 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) a battery cell
26. 26.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) ironing the paper (d) reading the message
27. 27.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
28. 28.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
29. 29.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
30. 30.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
31. 31.True or false: putting the iron away is a job a child can do. (a) True (b) False
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
33. 33.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) lemon juice (d) white paper
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the ironing time (c) how dark the writing is
36. 36.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a balloon (c) a magnet (d) a mirror
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
38. 38.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
39. 39.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
40. 40.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed

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