Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 944 · 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) plugging in the iron (b) dipping the cotton bud (c) reading the message (d) letting the paper dry
2. 2.True or false: yeast is needed for the secret lemon message. (a) True (b) False
3. 3.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
4. 4.⚖️ 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
5. 5.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) a magnet (d) a battery cell
6. 6.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do 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 measure it (b) we change it (c) we keep it the same
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a mirror (c) a small bowl (d) a magnet
9. 9.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) dipping the cotton bud (d) putting the iron away
10. 10.True or false: putting the iron away is a job a child can do. (a) False (b) True
11. 11.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
12. 12.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) letting the paper dry (d) writing the message
13. 13.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
14. 14.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
16. 16.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
17. 17.True or false: letting the paper dry is a job for an adult. (a) True (b) False
18. 18.⚖️ 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
19. 19.⚖️ 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 measure it (c) we change it
20. 20.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
21. 21.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
22. 22.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown
23. 23.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
24. 24.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
25. 25.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
26. 26.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) yeast (d) a magnet
27. 27.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
28. 28.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) cutting the lemon
29. 29.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) the paper ate it (d) dry juice is see-through
30. 30.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
31. 31.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
32. 32.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
33. 33.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
34. 34.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
35. 35.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
36. 36.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) plugging in the iron (d) ironing the paper
37. 37.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a balloon (d) white paper
38. 38.⚖️ 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 cotton bud (d) the iron setting
39. 39.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
40. 40.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False

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