Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 780 · 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? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
2. 2.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
3. 3.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
4. 4.⚖️ 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) the same cotton bud (c) the kind of juice (d) the ironing time
5. 5.🔍 Which is the odd one out? (a) writing the message (b) putting the iron away (c) dipping the cotton bud (d) letting the paper dry
6. 6.⚖️ 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 keep it the same (c) we measure it
7. 7.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) ironing the paper (d) writing the message
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) lemon juice (d) white paper
9. 9.True or false: cutting the lemon is a job a child can do. (a) True (b) False
10. 10.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) letting the paper dry (d) ironing the paper
11. 11.True or false: writing the message is a job for an adult. (a) False (b) True
12. 12.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
13. 13.⚖️ 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 same paper (c) how dark the writing is
14. 14.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) letting the paper dry (d) writing the message
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
16. 16.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) plugging in the iron (d) putting the iron away
17. 17.True or false: putting the iron away is a job for an adult. (a) True (b) False
18. 18.⚖️ 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) True (b) False
19. 19.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
20. 20.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a magnet (d) white paper
22. 22.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) lick your fingers (d) skip washing
23. 23.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
24. 24.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
25. 25.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) white paper (d) yeast
26. 26.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is magnetic (d) it is cold
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) a small bowl (d) a magnet
28. 28.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
29. 29.⚖️ 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
30. 30.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
31. 31.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) putting the iron away (d) plugging in the iron
32. 32.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
33. 33.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if cooled (d) yes, if shaken
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the ironing time (c) how dark the writing is (d) the kind of juice
35. 35.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) heat adds colour (d) paper turns lemony
36. 36.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
37. 37.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
38. 38.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
39. 39.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) reading the message (d) dipping the cotton bud
40. 40.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) the paper floats (d) writing turns green

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