Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 152 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) white paper (c) an adult with an iron (d) a cotton bud
2. 2.🛟 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
3. 3.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) letting the paper dry (c) ironing the paper (d) putting the iron away
4. 4.⚖️ 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
5. 5.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
6. 6.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
7. 7.🔍 Which is the odd one out? (a) cutting the lemon (b) reading the message (c) dipping the cotton bud (d) writing the message
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
9. 9.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) dipping the cotton bud (d) writing the message
10. 10.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
11. 11.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) reading the message (d) dipping the cotton bud
12. 12.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
13. 13.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
14. 14.True or false: ironing the paper is a job for an adult. (a) False (b) True
15. 15.True or false: reading the message is a job for an adult. (a) True (b) False
16. 16.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) the ink is magnetic (d) it turned into air
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a balloon (d) white paper
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.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) writing the message (c) cutting the lemon (d) ironing the paper
22. 22.⚖️ 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 kind of juice (c) how dark the writing is (d) the same paper
23. 23.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) writing the message (d) cutting the lemon
24. 24.⚖️ 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
25. 25.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
26. 26.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) it gets darker (d) writing stays faint
27. 27.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
28. 28.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
29. 29.True or false: writing the message is a job for an adult. (a) False (b) True
30. 30.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) dipping the cotton bud
31. 31.⚖️ 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
32. 32.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
33. 33.True or false: reading the message is a job a child can do. (a) True (b) False
34. 34.True or false: putting the iron away is a job a child can do. (a) True (b) False
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a cotton bud (d) yeast
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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) a cotton bud (c) an adult with an iron (d) a small bowl
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 lemon juice for the secret lemon message? (a) not needed (b) needed
40. 40.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) paper turns lemony (d) the juice scorches first

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