Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 456 · 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.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
2. 2.🧺 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 mirror
3. 3.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) reading the message (d) putting the iron away
4. 4.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a balloon (d) lemon juice
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the same cotton bud (d) the same paper
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) lemon juice (d) turmeric powder
11. 11.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
12. 12.⚖️ 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
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a magnet (c) a cotton bud (d) a small bowl
15. 15.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
16. 16.⚖️ 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 same paper (c) how dark the writing is
17. 17.🍋 Which of these steps is a job for an adult? (a) writing the message (b) cutting the lemon (c) reading the message (d) letting the paper dry
18. 18.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a battery cell (d) an adult with an iron
20. 20.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
21. 21.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
22. 22.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
23. 23.⚖️ 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
24. 24.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
25. 25.🍋 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
26. 26.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) a mirror (d) white paper
27. 27.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
28. 28.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
31. 31.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
32. 32.True or false: writing the message is a job for an adult. (a) False (b) True
33. 33.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
34. 34.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) reading the message (d) writing the message
35. 35.True or false: reading the message is a job a child can do. (a) False (b) True
36. 36.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
38. 38.True or false: putting the iron away is a job a child can do. (a) False (b) True
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud
40. 40.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) a rainbow (d) dark brown words

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