Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 893 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
2. 2.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
3. 3.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) writing the message
4. 4.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) putting the iron away (d) ironing the paper
5. 5.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
6. 6.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
7. 7.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
8. 8.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) lemon juice (d) a magnet
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
11. 11.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
12. 12.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
15. 15.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) almost nothing (d) a rainbow
16. 16.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) dipping the cotton bud (d) cutting the lemon
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) a small bowl (d) an adult with an iron
18. 18.🍋 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
19. 19.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) lemon juice (c) yeast (d) a battery cell
20. 20.True or false: ironing the paper is a job for an adult. (a) True (b) False
21. 21.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
22. 22.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) lick your fingers (d) skip washing
23. 23.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a balloon
25. 25.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) writing the message (d) letting the paper dry
26. 26.True or false: putting the iron away is a job a child can do. (a) True (b) False
27. 27.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
28. 28.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
29. 29.⚖️ 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
30. 30.⚖️ 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 same cotton bud (c) how dark the writing is (d) the iron setting
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) lemon juice (d) a cotton bud
33. 33.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) letting the paper dry (d) writing the message
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) a small bowl (c) a cotton bud (d) lemon juice
35. 35.⚖️ 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
36. 36.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
37. 37.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
38. 38.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
40. 40.⚖️ 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

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