Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 990 · 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.🔮 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
2. 2.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
3. 3.True or false: putting the iron away is a job a child can do. (a) True (b) False
4. 4.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) letting the paper dry
5. 5.True or false: ironing the paper is a job for an adult. (a) True (b) False
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a battery cell (d) white paper
7. 7.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) a balloon (d) yeast
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
10. 10.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
11. 11.🍋 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
12. 12.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) any child (d) only an adult
13. 13.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
14. 14.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) letting the paper dry (d) ironing the paper
15. 15.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it is magnetic (d) it can burn skin
16. 16.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
17. 17.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) putting the iron away (d) letting the paper dry
18. 18.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
19. 19.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
20. 20.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
21. 21.True or false: cutting the lemon is a job for an adult. (a) False (b) True
22. 22.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
23. 23.⚖️ 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
24. 24.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a balloon (d) white paper
26. 26.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) magnetic (d) chemical
27. 27.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) reading the message
28. 28.⚖️ 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
29. 29.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
30. 30.True or false: reading the message is a job for an adult. (a) False (b) True
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
33. 33.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
34. 34.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) dipping the cotton bud (d) plugging in the iron
35. 35.⚖️ 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
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) an adult with an iron (d) a magnet
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) how dark the writing is (c) the ironing time (d) the iron setting
38. 38.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
40. 40.⚖️ 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

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