Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 886 · 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? True or false: the ironing time is what we measure. (a) True (b) False
2. 2.⚖️ 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
3. 3.🔮 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
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a mirror (d) a cotton bud
5. 5.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) dipping the cotton bud (d) ironing the paper
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
7. 7.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) ironing the paper
8. 8.⚖️ 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
9. 9.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
10. 10.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
11. 11.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) writing the message
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) how dark the writing is (c) the kind of juice (d) the same paper
13. 13.True or false: reading the message is a job a child can do. (a) False (b) True
14. 14.⚖️ 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) False (b) True
15. 15.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
16. 16.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
17. 17.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) reading the message (c) dipping the cotton bud (d) letting the paper dry
18. 18.⚖️ 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
19. 19.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
20. 20.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) cutting the lemon (c) reading the message (d) writing the message
21. 21.⚖️ 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) how dark the writing is (d) the ironing time
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) an adult with an iron (d) turmeric powder
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold
24. 24.⚖️ 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 change it (c) we measure it
25. 25.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
26. 26.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
27. 27.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
29. 29.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) a balloon (d) lemon juice
31. 31.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
32. 32.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
33. 33.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
34. 34.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) skip washing (d) rub your eyes
35. 35.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) putting the iron away (d) plugging in the iron
36. 36.🍋 Which of these steps is a job a child can do? (a) reading the message (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
37. 37.True or false: letting the paper dry is a job for an adult. (a) True (b) False
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
39. 39.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True

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