Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 645 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
3. 3.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
4. 4.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
5. 5.True or false: cutting the lemon is a job for an adult. (a) False (b) True
6. 6.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) a battery cell (d) a cotton bud
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) a small bowl (d) turmeric powder
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) a cotton bud (d) an adult with an iron
10. 10.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) letting the paper dry
11. 11.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
12. 12.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) a mirror (d) white paper
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the same cotton bud
14. 14.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) ironing the paper
15. 15.🛟 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
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
17. 17.⚖️ 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
18. 18.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
19. 19.🍋 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) letting the paper dry
20. 20.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) letting the paper dry (d) plugging in the iron
21. 21.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
22. 22.⚖️ 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 paper
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) lemon juice (d) yeast
24. 24.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
25. 25.⚖️ 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) False (b) True
26. 26.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) heat adds colour (d) paper turns lemony
27. 27.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) it gets darker (d) the paper floats
28. 28.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) writing the message (d) dipping the cotton bud
29. 29.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
30. 30.🍋 Which of these steps is a job a child can do? (a) writing the message (b) cutting the lemon (c) putting the iron away (d) ironing the paper
31. 31.True or false: letting the paper dry is a job for an adult. (a) True (b) False
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
33. 33.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the kind of juice (c) the ironing time (d) how dark the writing is
35. 35.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) putting the iron away (d) plugging in the iron
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
37. 37.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
38. 38.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) plugging in the iron (d) reading the message
39. 39.🍋 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
40. 40.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it

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