Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 903 · 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? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
2. 2.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
3. 3.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
4. 4.⚖️ 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 iron setting (c) the same cotton bud (d) how dark the writing is
5. 5.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) letting the paper dry (c) cutting the lemon (d) putting the iron away
6. 6.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) white paper (d) yeast
8. 8.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a mirror (d) white paper
10. 10.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a balloon (c) a magnet (d) a battery cell
11. 11.⚖️ 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) True (b) False
12. 12.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) a magnet (d) a cotton bud
13. 13.True or false: reading the message is a job a child can do. (a) True (b) False
14. 14.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
15. 15.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
16. 16.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) reading the message
17. 17.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
19. 19.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) letting the paper dry (d) reading the message
20. 20.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air
21. 21.⚖️ 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 iron setting
22. 22.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) rub your eyes (d) wash your hands
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the ironing time (c) the kind of juice (d) the same cotton bud
25. 25.True or false: writing the message is a job a child can do. (a) True (b) False
26. 26.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
27. 27.⚖️ 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) the same paper (c) how dark the writing is
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) turmeric powder (c) lemon juice (d) a small bowl
29. 29.⚖️ 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
30. 30.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
31. 31.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
32. 32.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
33. 33.🛟 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
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
35. 35.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
36. 36.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
37. 37.⚖️ 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
38. 38.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) plugging in the iron (d) letting the paper dry
39. 39.🍋 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
40. 40.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it

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