Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 209 · 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.🔮 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
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) turmeric powder (d) lemon juice
3. 3.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
4. 4.🧺 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 mirror (d) a small bowl
5. 5.True or false: writing the message is a job for an adult. (a) False (b) True
6. 6.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
8. 8.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the ironing time (c) the same paper (d) how dark the writing is
10. 10.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
11. 11.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) lemon juice (d) a battery cell
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) a battery cell (d) a small bowl
14. 14.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) putting the iron away (d) cutting the lemon
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
16. 16.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) white (d) green
17. 17.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
18. 18.True or false: putting the iron away is a job for an adult. (a) True (b) False
19. 19.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
20. 20.⚖️ 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
21. 21.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) white paper (d) a cotton bud
24. 24.⚖️ 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 keep it the same (c) we measure it
25. 25.True or false: letting the paper dry is a job for an adult. (a) False (b) True
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
27. 27.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) wash your hands (d) lick your fingers
28. 28.⚖️ 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 same cotton bud (d) the ironing time
29. 29.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a battery cell (d) an adult with an iron
30. 30.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) letting the paper dry (d) ironing the paper
31. 31.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) turmeric powder (d) lemon juice
33. 33.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
34. 34.⚖️ 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
35. 35.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) putting the iron away (d) writing the message
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
37. 37.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
38. 38.🧺 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) an adult with an iron
39. 39.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
40. 40.True or false: cutting the lemon is a job for an adult. (a) False (b) True

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