Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 669 · 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.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) wash your hands (d) rub your eyes
3. 3.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
4. 4.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
5. 5.True or false: white paper is needed for the secret lemon message. (a) True (b) False
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a battery cell (c) a small bowl (d) white paper
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) lemon juice (d) white paper
9. 9.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it can burn skin (d) it is cold
10. 10.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
13. 13.⚖️ 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
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) yeast (d) a small bowl
15. 15.True or false: putting the iron away is a job for an adult. (a) False (b) True
16. 16.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) plugging in the iron
17. 17.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
19. 19.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) magnetic (d) musical
20. 20.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) a magnet (d) white paper
22. 22.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a mirror (d) white paper
24. 24.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
25. 25.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same cotton bud (c) the same paper (d) the kind of juice
27. 27.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, in the dark (d) yes, if cooled
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: cutting the lemon is a job for an adult. (a) False (b) True
30. 30.True or false: yeast is needed for the secret lemon message. (a) False (b) True
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) lemon juice (c) yeast (d) a battery cell
32. 32.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
33. 33.⚖️ 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
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) lemon juice (d) white paper
36. 36.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) a cotton bud (d) a small bowl
38. 38.True or false: reading the message 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 kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
40. 40.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it

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