Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 356 · 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 of these is needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) a battery cell (d) yeast
2. 2.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) whoever is fastest (d) only an adult
3. 3.⚖️ 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 same cotton bud (c) the kind of juice (d) how dark the writing is
4. 4.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
6. 6.⚖️ 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
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) lemon juice (d) a balloon
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) brown (d) green
9. 9.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
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 kind of juice (b) the same paper (c) the iron setting (d) the ironing time
11. 11.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) plugging in the iron
12. 12.True or false: letting the paper dry is a job a child can do. (a) False (b) True
13. 13.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
15. 15.⚖️ 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
16. 16.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
17. 17.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
18. 18.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) writing the message (d) cutting the lemon
19. 19.⚖️ 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 measure it (c) we keep it the same
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) writing stays faint (d) the paper floats
21. 21.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
22. 22.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a battery cell (c) a cotton bud (d) white paper
25. 25.True or false: cutting the lemon is a job for an adult. (a) True (b) False
26. 26.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
28. 28.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) putting the iron away (d) reading the message
29. 29.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
30. 30.🍋 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) cutting the lemon
31. 31.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
32. 32.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) plugging in the iron (d) dipping the cotton bud
33. 33.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) a cotton bud (d) a small bowl
35. 35.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
36. 36.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) a small bowl (d) an adult with an iron
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) dipping the cotton bud (b) reading the message (c) putting the iron away (d) writing the message
40. 40.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True

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