Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 644 · 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.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony
2. 2.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
3. 3.🛟 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
4. 4.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
5. 5.🔮 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
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the same cotton bud (c) the kind of juice
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) an adult with an iron (c) a small bowl (d) white paper
8. 8.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) reading the message (d) writing the message
9. 9.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
10. 10.True or false: plugging in the iron is a job a child can do. (a) False (b) True
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) lemon juice (c) an adult with an iron (d) a cotton bud
12. 12.⚖️ 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) False (b) True
13. 13.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
14. 14.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) writing the message (c) letting the paper dry (d) reading the message
15. 15.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) physical (d) magnetic
16. 16.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) reading the message
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a mirror (d) lemon juice
18. 18.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) lemon juice (c) a small bowl (d) white paper
20. 20.True or false: cutting the lemon is a job a child can do. (a) False (b) True
21. 21.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) a magnet (d) lemon juice
22. 22.🍋 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) writing the message
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the iron setting (c) the same paper (d) the same cotton bud
24. 24.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
25. 25.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
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.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) letting the paper dry (d) ironing the paper
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
29. 29.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
30. 30.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
31. 31.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) ironing the paper
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
33. 33.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
34. 34.True or false: putting the iron away is a job for an adult. (a) True (b) False
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) white paper (d) turmeric powder
36. 36.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
38. 38.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
39. 39.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
40. 40.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) reading the message (c) plugging in the iron (d) cutting the lemon

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