Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 210 · 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.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
2. 2.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) writing the message (d) plugging in the iron
3. 3.⚖️ 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 ironing time (c) the kind of juice
4. 4.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is cold (d) it is sticky
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 kind of juice (b) the ironing time (c) the same paper (d) the iron setting
6. 6.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) letting the paper dry (d) reading the message
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) a small bowl (d) a cotton bud
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
11. 11.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) a rainbow (d) dark brown words
12. 12.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
13. 13.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
14. 14.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
15. 15.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) writing the message
16. 16.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
17. 17.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
18. 18.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) dipping the cotton bud (d) plugging in the iron
19. 19.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
20. 20.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
21. 21.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) writing the message (d) ironing the paper
22. 22.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
23. 23.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
24. 24.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) plugging in the iron (d) putting the iron away
25. 25.⚖️ 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) False (b) True
26. 26.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) yeast (d) a small bowl
28. 28.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: reading the message is a job a child can do. (a) False (b) True
30. 30.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
31. 31.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a mirror (d) an adult with an iron
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a battery cell
34. 34.True or false: letting the paper dry is a job a child can do. (a) False (b) True
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) lemon juice (d) a small bowl
36. 36.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) a magnet (d) lemon juice
38. 38.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
39. 39.True or false: writing the message is a job a child can do. (a) True (b) False
40. 40.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False

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