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What is the reason sliced apples turn brown when left out?

• Oxidation
• Fermentation
• Rotting
• Dehydration

Have you ever bitten into an apple, set it down for a few moments, and found that it has turned brown? This is caused by an enzyme (polyphenol oxidase and catechol oxidase are two common examples) that reacts with oxygen in the air and an iron or copper cofactor in the fruit. A cofactor is a component that is necessary for a certain enzymatic reactions to happen. The fruit starts to oxidize when electrons are lost to another molecule (in this case, the air), and the food turns brown. In other words, it’s like edible rust on your food! Oxidation can be prevented or slowed down by not allowing oxygen to get to the surface of the fruit. To accomplish this, you can cook the food, which destroys the enzyme. It is also possible to prevent browning without cooking by covering the fruit (preventing air from reaching the fruit), or by lowering the pH on the surface, making it more acidic.

Source: Massachusetts Farm To School

Which everyday product can be used to clean mold?

• Detergent
• Vinegar
• Oil
• Water

Vinegar is mildly acidic and kills up to 82% of mold species. It is also natural and one of the safest products you can use to clean. You will not have to worry about using it around children or pets. White vinegar is extremely inexpensive and has many other helpful uses around the house. Therefore, it is beneficial to always keep a gallon jug in with your cleaning supplies.

Source: Maid Heathy

Why does soda fizz when you open the can?

• Carbon dioxide gas escapes
• Liquid boils
• Metal of the can shrinks
• Sugar dissolves

Carbon dioxide is made from one carbon atom and two oxygen atoms. The molecules of carbon dioxide are thoroughly mixed and dissolved into the water in the soda pop. When you open a soda can or bottle, the Carbon dioxide gas escapes from the soda and into the air. Eventually, enough will come out, and the soda will become flat.

Source: ACS

Which force pulls the ink down toward the paper in a ballpoint pen?

• Acceleration
• Torque
• Gravity
• Friction

The vital key to what makes a ballpoint pen tick is its bearing ball, which is found at the very tip of the nib. This bearing ball is a minuscule metal sphere, usually made of either brass, steel, or tungsten carbide. Gravity pulls the ink in the refill cartridge toward the tip of the pen, coating one-half of the bearing ball. As the writer moves the tip of the pen across a paper, the bearing ball rotates in its socket, transferring ink from the inside of the ink reservoir to the paper.

Source: Goldspot

Which of these processes releases oxygen into the atmosphere?

• Recreation
• Photosynthesis
• Respiration
• Inspiration

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar. During photosynthesis, plants take in carbon dioxide (CO2) and water (H2O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air, and stores energy within the glucose molecules.

Source: National Geographic

Microwave ovens cook using which form of energy?

• Chemical Energy
• Nuclear Fission
• Electromagnetic Radiation
• Heat

Microwaves are a form of "electromagnetic" radiation; that is, they are waves of electrical and magnetic energy moving together through space. Electromagnetic radiation spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an X-ray machine uses yet another portion.

Source: US Food and Drug Administration

If a living organism is bioluminescent, it emits what?

• Light
• Gas
• Heat
• Sound

Bioluminescence is the production and emission of light by a living organism. The light emitted by a bioluminescent organism is produced by energy released from chemical reactions occurring inside (or ejected by) the organism. While the functions of bioluminescence are not known for all animals, typically bioluminescence is used to warn or evade predators), to lure or detect prey, and to communication between members of the same species.

Source: National Ocean Service

What is the chemical symbol for iron?

• H
• Fe
• Au
• Na

Iron is a chemical element with the symbol Fe and atomic number 26. The symbol Fe is derived from the Latin ferrum for "firmness." Classified as a transition metal, iron is a solid at room temperature. Archaeological evidence suggests that people have been using iron for at least 5,000 years. Iron is cheap and one of the most abundant of all metals, comprising nearly 5.6% of the earth's crust.

Source: Pub Chem

What do we call the process of a solid becoming a liquid?

• Evaporation
• Melting
• Desublimation
• Freezing

A change of state is a physical change in a matter. They are reversible changes and do not involve any changes in the chemical makeup of the matter. If you took out the ice cubes from the freezer and placed them in a warm room, the ice would absorb energy from the warmer air around them. This absorbed energy would facilitate them to overcome the force of attraction holding them together, enabling them to slip out of the fixed position that they held as ice. The process in which a solids change to a liquid is called melting.

Source: BYJUS

Besides an earthquake, what other phenomena can cause a tsunami?

• Blizzard
• Volcanic eruption
• Hurricane
• Typhoon

Volcanic eruptions, submarine landslides, and coastal rock falls can also generate a tsunami, as can a large asteroid impacting the ocean. They originate from a vertical movement of the sea floor with the consequent displacement of water mass. Although relatively infrequent, violent volcanic eruptions represent also impulsive disturbances, which can displace a great volume of water and generate extremely destructive tsunami waves in the immediate source area. According to this mechanism, waves may be generated by the sudden displacement of water caused by a volcanic explosion, by a volcanos slope failure, or more likely by a phreatomagmatic explosion and collapse/engulfment of the volcanic magmatic chambers. One of the largest and most destructive tsunamis ever recorded was generated in August 26, 1883 after the explosion and collapse of the volcano of Krakatoa (Krakatau), in Indonesia.

Source: Indian Ocean Unesco

What is the common name given to the outer layer of the earth?

• Layer
• Crust
• Core
• Mantle

Earth's crust is Earth's thin outer shell of rock, regarding for less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The lithosphere is broken into tectonic plates whose motion allows heat to escape from the interior of the Earth into space.

Source: Wikipedia

Due to its motion, what type of energy does an object possess?

• Kinetic
• Elastic
• Potential
• Chemical

In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.

Source: Wikipedia

What does the pH scale measure?

• Acidity
• Color
• Humidity
• Voltage

The pH scale measures how acidic an object is. Objects that are not very acidic are called basic. The scale has values ranging from zero (the most acidic) to 14 (the most basic). For example, pure water has a pH value of 7. This value is considered neutral—neither acidic nor basic. Normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. However, when rain combines with sulfur dioxide or nitrogen oxides—produced by power plants and automobiles—the rain becomes much more acidic. Typical acid rain has a pH value of 4.0. A decrease in pH values from 5.0 to 4.0 means that the acidity is 10 times greater.

Source: USGS

Earth's tilted axis directly causes which of these phenomena?

• Earthquakes
• Volcanic eruptions
• Seasons
• Ocean currents

Earth's axis is an imaginary pole going right through the center of Earth from "top" to "bottom." Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth's surface gets some of each. Earth's tilted axis causes the seasons. Throughout the year, different parts of Earth receive the Sun's most direct rays. So, when the North Pole tilts toward the Sun, it's summer in the Northern Hemisphere. And when the South Pole tilts toward the Sun, it's winter in the Northern Hemisphere.

Source: NASA Spaceplace

Which of these elements has better electrical conductivity?

• Silver
• Copper
• Gold
• Iron

Conductivity refers to the ability of a material to transmit energy. There are different types of conductivity, including electrical, thermal, and acoustical conductivity. The most electrically conductive element is silver, followed by copper and gold. Silver also has the highest thermal conductivity of any element and the highest light reflectance. Although it is the best conductor, copper, and gold are used more often in electrical applications because copper is less expensive and gold has a much higher corrosion resistance.

Source: ThoughtCo

What term describes how much water vapor is in the air?

• Absolute humidity
• Precipitation
• Atmospheric pressure
• Afterglow

The amount of water vapor in the air is called absolute humidity. The amount of water vapor in the air as compared with the amount of water that the air could hold is called relative humidity. This amount of space in the air that can hold water changes depending on the temperature and pressure. The dew point is the temperature when water will start to condense out of the air.

Source: Center For Science Education

What caused the tilt of the Leaning Tower of Pisa?

• Unstable subsoil
• It was hit by a hurricane
• Poor material quality
• Humidity

The Leaning Tower of Pisa is the freestanding bell tower of the cathedral of the Italian city of Pisa. Famous for its unintended tilt, the 184 feet tower took nearly 200 years to build. Work started in 1173, and five years later, it started tilting. The tilt was noticeable as workers were making the second floor. The shift was caused by shallow foundations of 9.9 feet and unstable subsoil. Engineers working on the tower in later years built upper floors with one side shorter than the other to compensate. That means the structure is curved as well as tilted. Work was slow and sometimes abandoned for decades as Pisa was often at war with nearby Florence, Genoa, and other city-states. They finally completed the tower in 1372. Engineers believe the tower's future is now secure for at least 200 years.

Source: Institution of Civil Engineers

What does the temperature at which water boils depend on?

• Fire intensity
• Gravity
• Pressure
• Acceleration

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding environmental pressure. A liquid in a partial vacuum, i.e., under a lower pressure, has a lower boiling point than when that liquid is at atmospheric pressure. Because of this, water boils at 99.97 °C (211.95 °F) under standard pressure at sea level, but at 93.4 °C (200.1 °F) at 1,905 meters (6,250 ft) altitude. For a given pressure, different liquids will boil at different temperatures.

Source: Wikipedia

Irish soda bread is made without what?

• Butter
• Flour
• Yeast
• Sugar

It’s called Irish Soda Bread because it’s made with baking soda instead of yeast. Because of this, it’s more dense than your everyday white sandwich bread. Hearty and rustic are the words that come to mind, and it tastes kind of nutty from the wholemeal flour. While dense, it still has an aerated crumb like “normal” bread.

Source: RecipeTin Eats