Invisible Ink Experiment Worksheet

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

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