Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 613 · 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.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
2. 2.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
3. 3.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) writing the message
4. 4.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a magnet (c) a small bowl (d) lemon juice
6. 6.⚖️ 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 keep it the same (c) we measure it
7. 7.⚖️ 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 measure it (c) we change it
8. 8.⚖️ 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) how dark the writing is (c) the same cotton bud (d) the ironing time
9. 9.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
10. 10.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
11. 11.⚖️ 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 change it (c) we keep it the same
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the iron setting (c) the kind of juice (d) how dark the writing is
13. 13.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
14. 14.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) white paper (d) a mirror
16. 16.🔮 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
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
18. 18.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
19. 19.True or false: putting the iron away is a job a child can do. (a) False (b) True
20. 20.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) a cotton bud (d) yeast
23. 23.🔮 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
24. 24.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) letting the paper dry (d) ironing the paper
25. 25.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) turmeric powder (d) a small bowl
26. 26.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) lemon juice (d) white paper
28. 28.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) letting the paper dry
29. 29.🍋 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
30. 30.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) cutting the lemon
31. 31.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) cutting the lemon (d) writing the message
32. 32.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
33. 33.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
35. 35.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
36. 36.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
37. 37.🍋 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
38. 38.True or false: letting the paper dry is a job for an adult. (a) True (b) False
39. 39.⚖️ 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
40. 40.⚖️ 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 change it (c) we measure it

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