Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 220 · 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.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it can burn skin (d) it is sticky
2. 2.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) plugging in the iron (d) putting the iron away
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) lemon juice (d) a balloon
4. 4.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) letting the paper dry (d) writing the message
5. 5.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
6. 6.True or false: cutting the lemon is a job for an adult. (a) False (b) True
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we measure it (c) we change it
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) white paper (c) a balloon (d) a magnet
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
10. 10.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) lemon juice (c) a balloon (d) a mirror
11. 11.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) magnetic (d) musical
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a mirror (d) a cotton bud
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a magnet (d) a small bowl
14. 14.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) paper turns lemony (d) the iron is brown
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a magnet (c) yeast (d) turmeric powder
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 change it (b) we keep it the same (c) we measure it
17. 17.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) the youngest child (d) any child
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
19. 19.True or false: plugging in the iron is a job a child can do. (a) True (b) False
20. 20.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
21. 21.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
22. 22.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) yeast (d) lemon juice
23. 23.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) writing turns green (d) it gets darker
24. 24.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) plugging in the iron (d) writing the message
25. 25.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
26. 26.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a cotton bud (d) a mirror
28. 28.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
29. 29.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) wash your hands (d) lick your fingers
30. 30.True or false: yeast is needed for the secret lemon message. (a) True (b) False
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a battery cell (c) white paper (d) lemon juice
32. 32.⚖️ 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 kind of juice (c) how dark the writing is (d) the iron setting
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the same paper (c) the ironing time (d) how dark the writing is
34. 34.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
35. 35.True or false: ironing the paper is a job for an adult. (a) True (b) False
36. 36.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
38. 38.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) putting the iron away (d) reading the message
39. 39.⚖️ 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
40. 40.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True

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