Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 135 · 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 cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
2. 2.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) writing the message (c) putting the iron away (d) cutting the lemon
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
4. 4.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) letting the paper dry (d) plugging in the iron
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a mirror (c) an adult with an iron (d) a cotton bud
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) turmeric powder (d) yeast
7. 7.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
8. 8.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
9. 9.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
10. 10.True or false: putting the iron away is a job for an adult. (a) False (b) True
11. 11.🧺 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
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
13. 13.⚖️ 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
14. 14.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) brown (d) white
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the kind of juice (d) the iron setting
17. 17.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
18. 18.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) ironing the paper (c) reading the message (d) letting the paper dry
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) a mirror (d) white paper
20. 20.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) dark brown words (d) blue words
23. 23.True or false: yeast is needed for the secret lemon message. (a) True (b) False
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) white paper (d) lemon juice
25. 25.True or false: cutting the lemon is a job a child can do. (a) True (b) False
26. 26.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
27. 27.True or false: reading the message is a job a child can do. (a) True (b) False
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) a balloon (d) a cotton bud
29. 29.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) writing the message
30. 30.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) rub your eyes (d) lick your fingers
31. 31.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is magnetic (d) it is sticky
32. 32.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) whoever is fastest (d) any child
33. 33.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) putting the iron away (d) dipping the cotton bud
34. 34.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) yeast (c) a mirror (d) a battery cell
35. 35.🔮 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
36. 36.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
37. 37.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
38. 38.🧺 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
39. 39.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
40. 40.⚖️ 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

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