Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 435 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) a cotton bud (d) white paper
2. 2.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) reading the message (d) letting the paper dry
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
4. 4.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
5. 5.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) a small bowl (d) a magnet
6. 6.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) writing turns green (d) it gets darker
7. 7.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
8. 8.True or false: yeast is needed for the secret lemon message. (a) False (b) True
9. 9.⚖️ 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
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the same cotton bud (c) how dark the writing is (d) the same paper
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
12. 12.🍋 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) letting the paper dry
13. 13.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
14. 14.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) skip washing (d) lick your fingers
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) turmeric powder (d) a small bowl
16. 16.🍋 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
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
18. 18.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
19. 19.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) putting the iron away (d) plugging in the iron
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) a small bowl (c) an adult with an iron (d) white paper
21. 21.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) plugging in the iron
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a balloon (d) a cotton bud
23. 23.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) lemon juice (d) a balloon
25. 25.⚖️ 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 iron setting (c) how dark the writing is
26. 26.⚖️ 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
27. 27.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) almost nothing (d) blue words
28. 28.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
29. 29.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
30. 30.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a magnet (c) a small bowl (d) lemon juice
32. 32.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
33. 33.True or false: plugging in the iron is a job for an adult. (a) True (b) False
34. 34.True or false: cutting the lemon is a job for an adult. (a) False (b) True
35. 35.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
36. 36.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
37. 37.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) putting the iron away (d) ironing the paper
38. 38.True or false: putting the iron away is a job for an adult. (a) True (b) False
39. 39.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) cutting the lemon
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) an adult with an iron (c) lemon juice (d) a cotton bud

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