Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 833 · 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.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a balloon (d) a cotton bud
3. 3.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
5. 5.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
6. 6.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) reading the message
7. 7.⚖️ 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
8. 8.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) lemon juice (d) a 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 measure it (b) we change it (c) we keep it the same
11. 11.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
12. 12.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
13. 13.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) ironing the paper (d) putting the iron away
14. 14.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) white paper (c) a balloon (d) a magnet
16. 16.True or false: plugging in the iron is a job a child can do. (a) False (b) True
17. 17.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
18. 18.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) writing the message (d) ironing the paper
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
20. 20.True or false: cutting the lemon is a job for an adult. (a) False (b) True
21. 21.True or false: letting the paper dry is a job for an adult. (a) True (b) False
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
23. 23.⚖️ 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
24. 24.True or false: ironing the paper is a job for an adult. (a) True (b) False
25. 25.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) letting the paper dry (d) reading the message
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the kind of juice (d) the same cotton bud
27. 27.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) ironing the paper (c) letting the paper dry (d) writing the message
28. 28.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
29. 29.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
30. 30.🍋 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
31. 31.True or false: writing the message is a job a child can do. (a) True (b) False
32. 32.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
33. 33.True or false: ironing the paper is a job a child can do. (a) False (b) True
34. 34.⚖️ 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) the iron setting (c) the same paper (d) how dark the writing is
35. 35.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) a mirror (d) a magnet
36. 36.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a cotton bud (d) a balloon
38. 38.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
39. 39.True or false: putting the iron away is a job a child can do. (a) True (b) False
40. 40.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) the paper floats (d) writing turns green

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