Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 844 · 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? Which of these is the one thing we change? (a) the same paper (b) the ironing time (c) the same cotton bud (d) the kind of juice
2. 2.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) letting the paper dry (d) ironing the paper
3. 3.True or false: yeast is needed for the secret lemon message. (a) True (b) False
4. 4.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
5. 5.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) wash your hands (d) lick your fingers
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
8. 8.⚖️ 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
9. 9.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the paper ate it (c) the ink is magnetic (d) it turned into air
10. 10.True or false: cutting the lemon is a job a child can do. (a) False (b) True
11. 11.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
12. 12.True or false: writing the message is a job a child can do. (a) False (b) True
13. 13.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
14. 14.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
15. 15.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, in the dark (d) yes, if shaken
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
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) False (b) True
19. 19.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
20. 20.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
21. 21.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) whoever is fastest (d) the youngest child
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
23. 23.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) ironing the paper (d) dipping the cotton bud
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
25. 25.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
26. 26.⚖️ 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
27. 27.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the iron setting (c) the kind of juice (d) the same paper
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
30. 30.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
31. 31.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) lemon juice (d) turmeric powder
33. 33.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is cold (d) it is magnetic
34. 34.⚖️ 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 paper
35. 35.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
36. 36.⚖️ 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
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) turmeric powder (c) an adult with an iron (d) lemon juice
38. 38.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) letting the paper dry
39. 39.True or false: putting the iron away is a job a child can do. (a) True (b) False
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) yeast (d) an adult with an iron

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