Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 936 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
2. 2.⚖️ 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
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) brown (d) white
4. 4.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) white paper (d) yeast
5. 5.⚖️ 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 keep it the same (c) we measure it
6. 6.⚖️ 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
7. 7.⚖️ 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
8. 8.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) a cotton bud (c) a small bowl (d) an adult with an iron
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
11. 11.True or false: ironing the paper is a job a child can do. (a) False (b) True
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a battery cell (c) a cotton bud (d) an adult with an iron
13. 13.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
14. 14.True or false: plugging in the iron is a job for an adult. (a) False (b) True
15. 15.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
16. 16.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
17. 17.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
18. 18.True or false: white paper is needed for the secret lemon message. (a) True (b) False
19. 19.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
20. 20.🔮 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
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
22. 22.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
23. 23.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) the juice scorches first (d) heat adds colour
24. 24.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
25. 25.True or false: putting the iron away is a job for an adult. (a) True (b) False
26. 26.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) the paper floats (d) writing stays faint
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a balloon (c) an adult with an iron (d) white paper
28. 28.True or false: ironing the paper is a job for an adult. (a) False (b) True
29. 29.True or false: cutting the lemon is a job a child can do. (a) True (b) False
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 change it (c) we keep it the same
31. 31.True or false: plugging in the iron is a job a child can do. (a) False (b) True
32. 32.🧺 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 small bowl (d) a mirror
33. 33.⚖️ 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
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) lemon juice (c) a small bowl (d) white paper
35. 35.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, in the dark (d) yes, if shaken
36. 36.🍋 Which of these steps is a job for an adult? (a) writing the message (b) cutting the lemon (c) dipping the cotton bud (d) reading the message
37. 37.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) writing the message (d) letting the paper dry
38. 38.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
39. 39.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
40. 40.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) cutting the lemon (d) letting the paper dry

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