Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 961 · 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.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
2. 2.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
3. 3.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
4. 4.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
5. 5.⚖️ 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
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the ironing time (c) how dark the writing is
7. 7.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a small bowl (d) a balloon
9. 9.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
10. 10.⚖️ 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) the kind of juice (c) the same cotton bud (d) the ironing time
11. 11.True or false: cutting the lemon is a job a child can do. (a) False (b) True
12. 12.True or false: writing the message is a job for an adult. (a) True (b) False
13. 13.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
14. 14.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
16. 16.⚖️ 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 measure it (c) we change it
17. 17.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
18. 18.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
20. 20.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) putting the iron away
21. 21.True or false: yeast is needed for the secret lemon message. (a) True (b) False
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a mirror (c) a small bowl (d) yeast
23. 23.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
24. 24.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the kind of juice (c) how dark the writing is (d) the ironing time
26. 26.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a mirror (d) lemon juice
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a cotton bud (d) a magnet
28. 28.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
29. 29.⚖️ 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
30. 30.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
31. 31.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
32. 32.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) the iron is brown (d) heat adds colour
33. 33.True or false: putting the iron away is a job for an adult. (a) False (b) True
34. 34.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
35. 35.⚖️ 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 keep it the same (c) we measure it
36. 36.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
37. 37.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) writing the message
38. 38.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
39. 39.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) reading the message (d) plugging in the iron
40. 40.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) dipping the cotton bud (d) writing the message

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