Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 557 · 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.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
2. 2.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
3. 3.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the paper ate it (d) the ink is magnetic
4. 4.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) heat adds colour (d) paper turns lemony
5. 5.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) turmeric powder (c) white paper (d) a battery cell
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the same cotton bud (c) the kind of juice (d) how dark the writing is
7. 7.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
8. 8.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) how dark the writing is (d) the same paper
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) turmeric powder (d) a cotton bud
11. 11.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) yeast (d) a mirror
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) white paper (c) a cotton bud (d) lemon juice
13. 13.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
14. 14.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
15. 15.⚖️ 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 ironing time
16. 16.True or false: reading the message is a job a child can do. (a) True (b) False
17. 17.⚖️ 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
18. 18.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) reading the message
19. 19.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
20. 20.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
21. 21.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) lemon juice (d) yeast
23. 23.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) putting the iron away (d) dipping the cotton bud
24. 24.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
25. 25.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) cutting the lemon (d) writing the message
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) lemon juice (d) a magnet
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a small bowl (d) lemon juice
28. 28.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
29. 29.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) wash your hands (d) rub your eyes
30. 30.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
32. 32.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) dipping the cotton bud (d) plugging in the iron
33. 33.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
34. 34.True or false: reading the message is a job for an adult. (a) False (b) True
35. 35.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
37. 37.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
39. 39.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) cutting the lemon
40. 40.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white

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