Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 157 · 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 is the odd one out? (a) reading the message (b) letting the paper dry (c) plugging in the iron (d) dipping the cotton bud
2. 2.⚖️ 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
3. 3.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
4. 4.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) writing the message
5. 5.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
6. 6.True or false: plugging in the iron is a job for an adult. (a) True (b) False
7. 7.True or false: ironing the paper is a job a child can do. (a) False (b) True
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green
9. 9.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
10. 10.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
11. 11.⚖️ 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
12. 12.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
13. 13.⚖️ 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 kind of juice (d) how dark the writing is
14. 14.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
15. 15.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
16. 16.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
17. 17.⚖️ 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
18. 18.True or false: writing the message is a job a child can do. (a) False (b) True
19. 19.⚖️ 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
20. 20.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
22. 22.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
23. 23.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) writing the message (d) dipping the cotton bud
24. 24.True or false: putting the iron away is a job for an adult. (a) True (b) False
25. 25.True or false: reading the message is a job a child can do. (a) True (b) False
26. 26.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) lemon juice (d) a mirror
27. 27.🛟 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
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) a cotton bud (d) a small bowl
29. 29.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) ironing the paper (d) putting the iron away
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
31. 31.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
32. 32.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) cutting the lemon (d) reading the message
33. 33.True or false: plugging in the iron is a job a child can do. (a) True (b) False
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) white paper (d) a balloon
35. 35.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) putting the iron away
36. 36.🛟 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
37. 37.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
38. 38.⚖️ 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 cotton bud (c) the iron setting (d) how dark the writing is
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
40. 40.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint

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