Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 93 · 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.True or false: putting the iron away is a job a child can do. (a) True (b) False
2. 2.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) yes, if shaken (d) no, it stays brown
3. 3.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
4. 4.True or false: writing the message is a job for an adult. (a) False (b) True
5. 5.True or false: plugging in the iron is a job a child can do. (a) True (b) False
6. 6.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) skip washing (d) rub your eyes
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) False (b) True
8. 8.🍋 Which of these steps is a job for an adult? (a) reading the message (b) cutting the lemon (c) letting the paper dry (d) writing the message
9. 9.⚖️ 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
10. 10.⚖️ 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
11. 11.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) the paper floats (d) writing stays faint
12. 12.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) an adult with an iron (d) turmeric powder
14. 14.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) putting the iron away (c) cutting the lemon (d) ironing the paper
15. 15.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
16. 16.🧺 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 magnet
17. 17.🍋 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
18. 18.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
19. 19.True or false: letting the paper dry is a job a child can do. (a) False (b) True
20. 20.⚖️ 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
21. 21.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
22. 22.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
23. 23.True or false: yeast is needed for the secret lemon message. (a) True (b) False
24. 24.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) reading the message (d) cutting the lemon
25. 25.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) cutting the lemon (d) putting the iron away
26. 26.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) a magnet (d) turmeric powder
27. 27.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) plugging in the iron (d) writing the message
28. 28.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) white paper (c) a small bowl (d) a cotton bud
30. 30.⚖️ 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
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
32. 32.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
33. 33.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
34. 34.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) ironing the paper
35. 35.🛟 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
36. 36.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) letting the paper dry
37. 37.⚖️ 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) True (b) False
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) lemon juice (d) a mirror
39. 39.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) writing the message
40. 40.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed

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