Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 804 · 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: a mirror is not needed for the secret lemon message. (a) False (b) True
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) magnetic (d) chemical
3. 3.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
4. 4.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
5. 5.⚖️ 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 keep it the same (c) we measure it
6. 6.True or false: plugging in the iron is a job for an adult. (a) False (b) True
7. 7.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) green (d) blue
9. 9.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
10. 10.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) writing the message (d) reading the message
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) white paper (d) a cotton bud
12. 12.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) dry juice is see-through (d) the ink is magnetic
13. 13.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
14. 14.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) letting the paper dry (d) ironing the paper
15. 15.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we keep it the same (c) we change it
17. 17.⚖️ 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) the same cotton bud (d) the kind of juice
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) turmeric powder (d) a small bowl
19. 19.🧺 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) a balloon (d) white paper
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a cotton bud (d) a battery cell
21. 21.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) writing the message
22. 22.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) the juice scorches first (d) heat adds colour
23. 23.True or false: cutting the lemon is a job a child can do. (a) True (b) False
24. 24.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) letting the paper dry (d) dipping the cotton bud
25. 25.True or false: cutting the lemon is a job for an adult. (a) True (b) False
26. 26.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is cold (d) it is sticky
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
28. 28.⚖️ 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
29. 29.True or false: putting the iron away is a job for an adult. (a) False (b) True
30. 30.⚖️ 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
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the kind of juice (c) how dark the writing is (d) the iron setting
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) a small bowl (d) white paper
34. 34.True or false: reading the message is a job for an adult. (a) False (b) True
35. 35.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) a mirror (d) lemon juice
37. 37.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
38. 38.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) lemon juice (d) a cotton bud
40. 40.True or false: yeast is not needed for the secret lemon message. (a) False (b) True

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