Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 324 · 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.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) heat adds colour (d) the iron is brown
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) chemical (d) musical
3. 3.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
4. 4.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the kind of juice (c) how dark the writing is (d) the iron setting
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a mirror (c) a cotton bud (d) an adult with an iron
7. 7.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) reading the message (d) plugging in the iron
8. 8.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) cutting the lemon (d) dipping the cotton bud
9. 9.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
10. 10.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
11. 11.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
12. 12.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
13. 13.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) white paper (c) a magnet (d) yeast
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) the ink is magnetic (d) it turned into air
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
17. 17.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
18. 18.⚖️ 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) False (b) True
19. 19.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
20. 20.🛟 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
21. 21.True or false: writing the message is a job a child can do. (a) False (b) True
22. 22.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) letting the paper dry
23. 23.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) putting the iron away (d) dipping the cotton bud
24. 24.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a magnet (c) white paper (d) lemon juice
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) yeast
27. 27.True or false: yeast is needed for the secret lemon message. (a) True (b) False
28. 28.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a battery cell (c) a cotton bud (d) lemon juice
30. 30.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
31. 31.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
32. 32.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
33. 33.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown
34. 34.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) white paper (d) an adult with an iron
36. 36.⚖️ 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
37. 37.🍋 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) writing the message
38. 38.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) turmeric powder (d) a magnet
39. 39.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) ironing the paper
40. 40.⚖️ 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 keep it the same (c) we change it

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