23,105 questions and answers — page 1 of 1156
📕 Print the encyclopedia / PDFLearn about Science Quizzes · Secrets of the Human Body 🫀 · Math Geniuses: Beginner
Answer: Jabir ibn Hayyan, then Abu Bakr al-Razi, then Antoine Lavoisier, then Dmitri Mendeleev
💡 Jabir ibn Hayyan is associated with the 8th century CE, al-Razi with the 9th and 10th centuries, Lavoisier with the 18th century, and Mendeleev with the 19th century.
Answer: True ✔
💡 Dissolved salt raises the boiling point of water slightly, so salt water needs a little more than 100 degrees Celsius to boil.
Answer: True ✔
💡 Marie Curie studied the radiation given off by some elements and coined the term "radioactivity," and with her husband Pierre she discovered polonium and radium in 1898.
Answer: Physics and chemistry
💡 Marie Curie won the Nobel Prize in Physics in 1903 with her husband Pierre and Henri Becquerel, then the Nobel Prize in Chemistry in 1911.
Answer: Abu Bakr al-Razi
💡 Abu Bakr al-Razi was a physician and chemist who lived in the 9th and 10th centuries CE; he is credited with classifying substances and describing lab tools and processes such as distillation.
Answer: Because the mixture releases dangerous toxic gases
💡 Mixing bleach with ammonia or some acidic cleaners releases toxic gases that harm the lungs, so each cleaner should be used alone with good ventilation.
Answer: Its molecules have one end attracted to water and one end attracted to grease, so it surrounds the grease and carries it away with the water
💡 Soap surrounds droplets of grease with its grease-loving ends, while its water-loving ends stay on the outside, so the water washes them away during rinsing.
Answer: Carbon dioxide
💡 Baking soda is a base and vinegar is an acid, and when they react, carbon dioxide gas is released, making bubbles and foam.
Answer: Bronze
💡 Bronze is an alloy of copper and tin, and it was so important that a whole era of human history was named "the Bronze Age."
Answer: Condensation
💡 Water vapor in the air cools when it touches the cold surface of the glass and turns into liquid; this is condensation.
Answer: Lemon juice, then Coffee, then Pure water, then Baking soda solution, then Household bleach
💡 Lemon juice is about 2, coffee about 5, pure water 7, baking soda solution about 9, and household bleach about 12 or higher.
Answer: Solid ↔ Has a fixed shape and a fixed volume, Liquid ↔ Has a fixed volume and takes the shape of its container, Gas ↔ Has no fixed shape or volume and spreads out to fill the space
💡 The particles of a solid are close together and held tightly, the particles of a liquid slide over one another, and the particles of a gas are far apart and move freely.
Answer: Acetic acid
💡 Vinegar contains a small amount of diluted acetic acid, which is responsible for its sour taste and distinctive smell.
Answer: A salt and water
💡 This reaction is called neutralization: the acid and the base cancel each other's effects and produce a salt and water.
Answer: It turns red
💡 Litmus paper is a simple indicator: acid turns blue paper red, and a base turns red paper blue.
Answer: False ✖
💡 Numbers above 7 mean the solution is basic, and the higher the number, the more basic it is, while acidity increases as the number goes lower below 7.
Answer: 7
💡 The pH scale usually runs from 0 to 14; 7 is neutral, anything below it is acidic, and anything above it is basic.
Answer: The mass of substances before a chemical reaction equals their mass after it
💡 In a chemical reaction, atoms are rearranged and are neither destroyed nor created, so the total mass stays the same if the gases produced are also counted.
Answer: Hydrogen and oxygen
💡 Water is a compound of hydrogen and oxygen, and an electric current breaks it down into them, with twice as much hydrogen produced by volume as oxygen.
Answer: Because the water suddenly turns to steam and throws the burning oil, spreading the fire
💡 Water is heavier than oil, so it sinks below it and boils off suddenly, throwing the burning oil around and making the fire bigger; the right thing to do is turn off the heat and cover the pan with its lid if it can be done safely.
