Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 5 · 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.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
2. 2.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
3. 3.True or false: writing the message is a job for an adult. (a) True (b) False
4. 4.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) how dark the writing is (c) the kind of juice (d) the iron setting
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) an adult with an iron (d) white paper
7. 7.True or false: ironing the paper is a job for an adult. (a) True (b) False
8. 8.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) heat adds colour (d) the iron is brown
9. 9.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
10. 10.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
11. 11.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
12. 12.🧺 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
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) a mirror (d) a cotton bud
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) yeast (d) lemon juice
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
17. 17.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) dry juice is see-through (d) it turned into air
18. 18.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
19. 19.True or false: white paper is needed for the secret lemon message. (a) False (b) True
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
21. 21.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
22. 22.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) rub your eyes (d) skip washing
23. 23.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) ironing the paper (d) writing the message
24. 24.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
25. 25.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if cooled (d) yes, if shaken
26. 26.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
27. 27.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
28. 28.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
29. 29.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) lemon juice (d) a magnet
31. 31.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
32. 32.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a small bowl (d) a battery cell
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
35. 35.⚖️ 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
36. 36.🛟 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
37. 37.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) a magnet (d) lemon juice
38. 38.🔮 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
39. 39.True or false: reading the message is a job a child can do. (a) False (b) True
40. 40.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) writing the message (d) dipping the cotton bud

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