Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 637 · 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.True or false: ironing the paper is a job a child can do. (a) True (b) False
2. 2.🔮 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
3. 3.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
4. 4.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a battery cell (c) a magnet (d) a mirror
5. 5.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a small bowl (d) turmeric powder
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
8. 8.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
9. 9.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) the youngest child (d) whoever is fastest
10. 10.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
11. 11.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
13. 13.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) heat adds colour (d) the iron is brown
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) a magnet (d) a mirror
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) how dark the writing is (c) the same paper (d) the ironing time
16. 16.🔮 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
17. 17.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) a rainbow (d) blue words
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
19. 19.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) reading the message (d) dipping the cotton bud
20. 20.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
21. 21.⚖️ 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
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 measure it (c) we change it
23. 23.True or false: writing the message is a job a child can do. (a) True (b) False
24. 24.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) cutting the lemon
25. 25.⚖️ 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) False (b) True
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
27. 27.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
29. 29.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
30. 30.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) ironing the paper (d) dipping the cotton bud
31. 31.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
32. 32.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) writing the message
33. 33.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
34. 34.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) writing the message
35. 35.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
36. 36.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
37. 37.⚖️ 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) the kind of juice (c) the same paper (d) how dark the writing is
38. 38.⚖️ 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
39. 39.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) letting the paper dry (d) cutting the lemon
40. 40.⚖️ 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

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