Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 60 · 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.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) reading the message (d) ironing the paper
2. 2.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
4. 4.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) dipping the cotton bud (d) reading the message
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 same paper (b) how dark the writing is (c) the same cotton bud (d) the kind of juice
6. 6.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
7. 7.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) almost nothing (d) a rainbow
8. 8.True or false: plugging in the iron is a job a child can do. (a) False (b) True
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) an adult with an iron (c) a cotton bud (d) lemon juice
10. 10.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
11. 11.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) lemon juice (d) a magnet
13. 13.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
14. 14.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) magnetic (d) musical
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a small bowl (c) yeast (d) turmeric powder
17. 17.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
18. 18.⚖️ 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
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
20. 20.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the paper ate it (c) the ink is magnetic (d) it turned into air
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) lemon juice (c) white paper (d) an adult with an iron
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a battery cell (d) white paper
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
24. 24.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
25. 25.True or false: cutting the lemon is a job for an adult. (a) True (b) False
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) yeast (d) a small bowl
27. 27.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
28. 28.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) letting the paper dry (d) putting the iron away
29. 29.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
30. 30.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) dipping the cotton bud
31. 31.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
33. 33.⚖️ 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
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
35. 35.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
36. 36.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) ironing the paper (d) reading the message
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) yeast (d) white paper
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a mirror (c) an adult with an iron (d) a cotton bud
39. 39.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) the youngest child (d) whoever is fastest
40. 40.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) lick your fingers (d) rub your eyes

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