Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 439 · 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) cutting the lemon (b) reading the message (c) dipping the cotton bud (d) letting the paper dry
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a magnet (c) an adult with an iron (d) a small bowl
3. 3.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a magnet (d) a cotton bud
5. 5.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
6. 6.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) lemon juice (c) a battery cell (d) yeast
7. 7.⚖️ 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
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
9. 9.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is cold (d) it is magnetic
10. 10.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
11. 11.⚖️ 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
12. 12.⚖️ 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
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
14. 14.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
17. 17.True or false: cutting the lemon is a job a child can do. (a) False (b) True
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) white paper (c) lemon juice (d) an adult with an iron
19. 19.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
20. 20.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
21. 21.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) reading the message (d) putting the iron away
22. 22.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) writing the message (d) ironing the paper
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a mirror (d) a cotton bud
24. 24.⚖️ 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
25. 25.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) white (d) green
26. 26.⚖️ 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
27. 27.True or false: yeast is needed for the secret lemon message. (a) False (b) True
28. 28.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) the paper floats (d) writing turns green
29. 29.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) yeast (d) a cotton bud
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) turmeric powder (d) an adult with an iron
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) an adult with an iron (d) a battery cell
33. 33.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
34. 34.True or false: reading the message is a job for an adult. (a) False (b) True
35. 35.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
36. 36.True or false: cutting the lemon is a job for an adult. (a) False (b) True
37. 37.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) ironing the paper (d) writing the message
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a balloon (d) white paper
39. 39.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
40. 40.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True

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