Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 305 · 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: cutting the lemon is a job a child can do. (a) False (b) True
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) white paper
4. 4.⚖️ 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 iron setting (c) the kind of juice
5. 5.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) a cotton bud (d) a magnet
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a mirror (c) turmeric powder (d) a small bowl
7. 7.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the iron setting (c) how dark the writing is (d) the kind of juice
9. 9.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
10. 10.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) cutting the lemon (c) putting the iron away (d) ironing the paper
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
12. 12.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
13. 13.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
14. 14.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
15. 15.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
16. 16.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
17. 17.True or false: putting the iron away is a job for an adult. (a) False (b) True
18. 18.🍋 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
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
20. 20.True or false: letting the paper dry is a job for an adult. (a) True (b) False
21. 21.⚖️ 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
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) a rainbow (d) blue words
23. 23.True or false: ironing the paper is a job for an adult. (a) True (b) False
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a battery cell (c) a cotton bud (d) white paper
25. 25.True or false: yeast is needed for the secret lemon message. (a) True (b) False
26. 26.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
28. 28.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
29. 29.🧺 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) white paper
30. 30.⚖️ 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
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
32. 32.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) letting the paper dry (d) ironing the paper
33. 33.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a small bowl (c) lemon juice (d) white paper
35. 35.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) it gets darker (d) writing stays faint
36. 36.True or false: white paper is needed for the secret lemon message. (a) False (b) True
37. 37.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) dipping the cotton bud (d) plugging in the iron
38. 38.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
39. 39.⚖️ 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
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) white paper (d) a battery cell

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