Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 609 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) paper turns lemony (d) the juice scorches first
3. 3.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) lemon juice (d) a mirror
5. 5.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) letting the paper dry
6. 6.⚖️ 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 cotton bud (d) the same paper
7. 7.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) ironing the paper (d) putting the iron away
8. 8.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
9. 9.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
10. 10.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
11. 11.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
12. 12.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) a balloon (d) a small bowl
13. 13.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) reading the message (d) putting the iron away
14. 14.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
15. 15.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
16. 16.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
17. 17.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) lemon juice (d) a cotton bud
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
21. 21.True or false: plugging in the iron is a job for an adult. (a) False (b) True
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
24. 24.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) reading the message (d) letting the paper dry
25. 25.True or false: letting the paper dry is a job for an adult. (a) False (b) True
26. 26.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
27. 27.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
29. 29.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) an adult with an iron (c) lemon juice (d) white paper
31. 31.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
33. 33.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) writing the message (c) plugging in the iron (d) ironing the paper
34. 34.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
35. 35.True or false: reading the message is a job a child can do. (a) True (b) False
36. 36.⚖️ 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 measure it (c) we change it
37. 37.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) an adult with an iron (d) a magnet
39. 39.🍋 Which of these steps is a job for an adult? (a) writing the message (b) ironing the paper (c) reading the message (d) letting the paper dry
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) lemon juice (d) white paper

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