Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 635 · 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.True or false: letting the paper dry is a job a child can do. (a) False (b) True
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) lick your fingers (d) skip washing
3. 3.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) ironing the paper (d) writing the message
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) a balloon (d) lemon juice
5. 5.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a mirror (c) a cotton bud (d) a magnet
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 ironing time (b) the same paper (c) how dark the writing is (d) the kind of juice
7. 7.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) heat adds colour (d) the iron is brown
8. 8.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
9. 9.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
10. 10.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) plugging in the iron (d) ironing the paper
11. 11.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) putting the iron away (d) ironing the paper
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) lemon juice (c) an adult with an iron (d) a small bowl
13. 13.⚖️ 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
14. 14.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
15. 15.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if cooled (d) yes, if shaken
16. 16.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) putting the iron away
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) yeast (d) an adult with an iron
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) green (d) brown
19. 19.⚖️ 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
20. 20.⚖️ 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
21. 21.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) writing the message (c) letting the paper dry (d) reading the message
22. 22.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
23. 23.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
24. 24.🔮 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
25. 25.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) lemon juice (c) a balloon (d) a battery cell
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) white paper (d) a balloon
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
28. 28.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
30. 30.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
31. 31.⚖️ 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
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) a magnet (d) white paper
33. 33.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) any child (d) whoever is fastest
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) a cotton bud (c) white paper (d) a small bowl
35. 35.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) cutting the lemon (d) dipping the cotton bud
36. 36.⚖️ 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
37. 37.True or false: putting the iron away is a job a child can do. (a) False (b) True
38. 38.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is sticky (d) it is magnetic
39. 39.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) cutting the lemon (c) writing the message (d) reading the message
40. 40.🔮 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

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