Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 518 · 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.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) letting the paper dry (d) writing the message
2. 2.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
3. 3.⚖️ 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) True (b) False
4. 4.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
5. 5.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
6. 6.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
7. 7.⚖️ 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
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) rub your eyes (d) skip washing
9. 9.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
11. 11.⚖️ 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
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
13. 13.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
14. 14.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) white (d) green
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a small bowl (d) a balloon
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
18. 18.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) it turned into air (d) the paper ate it
19. 19.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
20. 20.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
21. 21.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) the youngest child (d) any child
22. 22.True or false: putting the iron away is a job for an adult. (a) False (b) True
23. 23.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
24. 24.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) reading the message (d) plugging in the iron
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the ironing time (c) the kind of juice (d) the iron setting
26. 26.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) the juice scorches first (d) paper turns lemony
27. 27.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) plugging in the iron (d) writing the message
28. 28.⚖️ 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
29. 29.True or false: writing the message is a job a child can do. (a) False (b) True
30. 30.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
31. 31.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing stays faint (d) writing turns green
32. 32.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, in the dark (d) yes, if shaken
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) white paper (d) lemon juice
34. 34.True or false: yeast is needed for the secret lemon message. (a) True (b) False
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) lemon juice (d) a mirror
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
37. 37.True or false: cutting the lemon is a job a child can do. (a) True (b) False
38. 38.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) reading the message (d) letting the paper dry
39. 39.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
40. 40.True or false: ironing the paper is a job a child can do. (a) True (b) False

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