Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 271 · 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.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
2. 2.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
3. 3.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
4. 4.🍋 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
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
7. 7.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) turmeric powder (d) white paper
8. 8.🔮 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
9. 9.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) a battery cell (d) lemon juice
11. 11.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
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 keep it the same (b) we measure it (c) we change it
13. 13.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
14. 14.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
15. 15.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) ironing the paper (d) reading the message
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) a cotton bud (c) lemon juice (d) white paper
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the ironing time (c) the kind of juice (d) how dark the writing is
19. 19.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) writing the message (d) letting the paper dry
20. 20.⚖️ 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
21. 21.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) reading the message (d) ironing the paper
22. 22.🍋 Which of these steps is a job a child can do? (a) writing the message (b) plugging in the iron (c) putting the iron away (d) ironing the paper
23. 23.⚖️ 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
24. 24.⚖️ 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 iron setting (c) how dark the writing is
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
26. 26.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
27. 27.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
28. 28.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) cutting the lemon (d) dipping the cotton bud
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
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 keep it the same (b) we measure it (c) we change it
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) yeast (d) a small bowl
32. 32.True or false: white paper is needed for the secret lemon message. (a) True (b) False
33. 33.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) white paper (c) turmeric powder (d) yeast
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
36. 36.True or false: cutting the lemon is a job for an adult. (a) True (b) False
37. 37.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
38. 38.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
39. 39.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) letting the paper dry
40. 40.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False

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