Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 693 · 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.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) an adult with an iron (d) white paper
2. 2.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) plugging in the iron (d) ironing the paper
3. 3.⚖️ 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 keep it the same (c) we measure it
4. 4.⚖️ 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 keep it the same (c) we measure it
5. 5.⚖️ 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 iron setting
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
7. 7.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a balloon (d) an adult with an iron
9. 9.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
10. 10.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
11. 11.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
12. 12.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) dry juice is see-through (d) the ink is magnetic
13. 13.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) a small bowl (d) yeast
15. 15.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) reading the message
16. 16.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) reading the message (d) letting the paper dry
17. 17.⚖️ 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
18. 18.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) white paper (c) a cotton bud (d) an adult with an iron
20. 20.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) wash your hands (d) rub your eyes
21. 21.True or false: putting the iron away is a job for an adult. (a) False (b) True
22. 22.⚖️ 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
23. 23.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) putting the iron away (d) plugging in the iron
24. 24.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) writing the message (d) reading the message
25. 25.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) yeast (c) a small bowl (d) white paper
27. 27.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
28. 28.⚖️ 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 ironing time (c) the kind of juice
29. 29.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) a cotton bud (d) an adult with an iron
31. 31.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
32. 32.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
35. 35.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) letting the paper dry
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
37. 37.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
38. 38.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
39. 39.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
40. 40.⚖️ 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

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