Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 727 · 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.⚖️ 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 ironing time (c) how dark the writing is
2. 2.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
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.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) an adult with an iron (d) a cotton bud
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) how dark the writing is (c) the kind of juice
6. 6.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the same paper (c) the kind of juice
8. 8.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) the juice scorches first (d) heat adds colour
9. 9.⚖️ 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 paper (c) the kind of juice (d) the same cotton bud
10. 10.⚖️ 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
11. 11.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
12. 12.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
13. 13.True or false: cutting the lemon is a job for an adult. (a) True (b) False
14. 14.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) writing the message (d) putting the iron away
15. 15.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
16. 16.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) reading the message (d) cutting the lemon
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a mirror (d) an adult with an iron
18. 18.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
19. 19.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) yeast (c) a battery cell (d) a magnet
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
21. 21.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
22. 22.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) a balloon (d) a cotton bud
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
25. 25.True or false: ironing the paper is a job for an adult. (a) True (b) False
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we keep it the same (c) we change it
27. 27.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
28. 28.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) writing the message (d) ironing the paper
29. 29.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a small bowl (c) a balloon (d) a mirror
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the iron setting (c) the ironing time (d) how dark the writing is
32. 32.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) ironing the paper (d) cutting the lemon
33. 33.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) lemon juice (d) a cotton bud
35. 35.⚖️ 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
36. 36.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) dipping the cotton bud
37. 37.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) reading the message (c) cutting the lemon (d) ironing the paper
38. 38.⚖️ 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
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a mirror
40. 40.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False

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