Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 471 · 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.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the paper ate it (d) the ink is magnetic
2. 2.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a small bowl (c) yeast (d) a battery cell
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a battery cell (c) white paper (d) an adult with an iron
4. 4.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
5. 5.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) reading the message
6. 6.⚖️ 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
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same cotton bud (c) how dark the writing is (d) the same paper
8. 8.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, if shaken (d) yes, in the dark
9. 9.🛟 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
10. 10.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
11. 11.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
12. 12.⚖️ 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) False (b) True
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) white paper (c) an adult with an iron (d) a small bowl
14. 14.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a magnet (d) white paper
16. 16.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) ironing the paper (c) plugging in the iron (d) putting the iron away
17. 17.⚖️ 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 change it (c) we measure it
18. 18.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) the juice scorches first (d) paper turns lemony
19. 19.⚖️ 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 kind of juice (c) the ironing time (d) the iron setting
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) a battery cell (d) an adult with an iron
21. 21.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
22. 22.⚖️ 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
23. 23.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
24. 24.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
25. 25.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
26. 26.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
27. 27.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) ironing the paper
28. 28.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
29. 29.⚖️ 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 same paper (c) how dark the writing is
30. 30.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) putting the iron away (d) plugging in the iron
31. 31.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) yeast (d) lemon juice
33. 33.⚖️ 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 measure it (c) we keep it the same
34. 34.True or false: plugging in the iron is a job a child can do. (a) True (b) False
35. 35.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
36. 36.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
37. 37.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) letting the paper dry
38. 38.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a cotton bud (d) a mirror
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) white paper (d) turmeric powder
40. 40.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False

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