Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 74 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) heat adds colour (d) the iron is brown
3. 3.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
4. 4.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
5. 5.🛟 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
6. 6.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
7. 7.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
8. 8.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
9. 9.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
10. 10.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
11. 11.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) plugging in the iron
12. 12.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a mirror (d) lemon juice
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) an adult with an iron (d) turmeric powder
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the iron setting (c) the same cotton bud (d) the kind of juice
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) lemon juice (d) a cotton bud
17. 17.🔮 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
18. 18.🧺 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) white paper
19. 19.⚖️ 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 measure it (c) we keep it the same
20. 20.⚖️ 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
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) an adult with an iron (d) a magnet
22. 22.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
23. 23.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
24. 24.True or false: putting the iron away is a job for an adult. (a) True (b) False
25. 25.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
26. 26.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) brown (d) white
27. 27.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) any child (d) only an adult
28. 28.🍋 Which of these steps is a job for an adult? (a) writing the message (b) putting the iron away (c) dipping the cotton bud (d) reading the message
29. 29.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) letting the paper dry
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
31. 31.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
32. 32.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
33. 33.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
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 ironing time (b) the same paper (c) the kind of juice (d) how dark the writing is
35. 35.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) letting the paper dry (d) ironing the paper
36. 36.⚖️ 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
37. 37.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
38. 38.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a balloon (d) a cotton bud
40. 40.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed

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