Answer the following question given this paragraph: Once excited, an atom or molecule will usually spontaneously de-excite quickly. (The electrons raised to higher levels are attracted to lower ones by the positive charge of the nucleus. ) Spontaneous de-excitation has a very short mean lifetime of 8 typically about 10 s . However, some levels have significantly longer lifetimes, ranging up to milliseconds to minutes or even hours. These energy levels are inhibited and are slow in de-exciting because their quantum numbers differ greatly from those of available lower levels. Although these level lifetimes are short in human terms, they are many orders of magnitude longer than is typical and, thus, are said to be metastable, meaning relatively stable. Phosphorescence is the de-excitation of a metastable state. Glow-in-the-dark materials, such as luminous dials on some watches and clocks and on children's toys and pajamas, are made of phosphorescent substances. Visible light excites the atoms or molecules to metastable states that decay slowly, releasing the stored excitation energy partially as visible light. In some ceramics, atomic excitation energy can be frozen in after the ceramic has cooled from its firing. It is very slowly released, but the ceramic can be induced to phosphoresce by heatinga process called "thermoluminescence. " Since the release is slow, thermoluminescence can be used to date antiquities. The less light emitted, the older the ceramic. (See Figure 30.35. Q: What makes luminous dials glow in the dark? Choices: - polymer substances - devil substances - eerie substances - phosphorescent substances A:
phosphorescent substances
Answer the following question given this paragraph: The stratosphere contains a layer of ozone gas. Ozone consists of three oxygen atoms (O 3 ). The ozone layer absorbs high-energy UV radiation. As you can see in Figure below , UV radiation splits the ozone molecule. The split creates an oxygen molecule (O 2 ) and an oxygen atom (O). This split releases heat that warms the stratosphere. By absorbing UV radiation, ozone also protects Earth's surface. UV radiation would harm living things without the ozone layer. Q: What is the name for the stratospheric gas layer that protects living things from uv radiation? Choices: - carbon layer - atmospheric layer - toposphere - ozone layer A:
ozone layer
Q: Answer the following question given this paragraph: Electromagnetic waves are waves that carry energy through matter or space as vibrating electric and magnetic fields. Electromagnetic waves have a wide range of wavelengths and frequencies. Sunlight contains the complete range of wavelengths of electromagnetic waves, which is called the electromagnetic spectrum. The Figure below shows all the waves in the spectrum. Q: What type of waves carry energy through matter or space as vibrating electric and magnetic fields? Choices: - light waves - mechanical waves - sound waves - electromagnetic waves A:
A: electromagnetic waves
Question: Answer the following question given this paragraph: During a thunderstorm, some parts of a thunderhead become negatively charged. Other parts become positively charged. The difference in charge creates lightning. Lightning is a huge release of electricity. Lightning can jump between oppositely charged parts of the same cloud, between one cloud and another, or between a cloud and the ground. You can see lightning in Figure below . Lightning blasts the air with energy. The air heats and expands so quickly that it explodes. This creates the loud sound of thunder . Q: What causes lightning during a thunderstorm? Choices: - difference in wind - difference in elevation - difference in temperature - difference in charge A:
Answer: difference in charge
*Question*
Answer the following question given this paragraph: Solid carbon dioxide is also called dry ice. That's because when it gets warmer and changes state, it doesn't change to a liquid by melting. Instead, it changes directly to a gas without going through the liquid state. The process in which a solid changes directly to a gas is called sublimation . It occurs when energy is added to a solid such as dry ice. You can watch dry ice changing directly to a gas in the video at this URL: http://www. youtube. com/watch?v=J8mDGwf-5x0 . Q: What is another term for dry ice? Choices: - liquid nitrogen - ice crystals - carbonated ice - solid carbon dioxide A:
**Answer**
solid carbon dioxide
Q: Answer the following question given this paragraph: Sperm are released into the surrounding water through the osculum. If they enter a female sponge through a pore, they may be trapped by collar cells. Trapped sperm are delivered to eggs inside the female body, where fertilization takes place. The resulting zygote develops into a larva. Unlike the adult, the larva is motile. It is covered with cilia that propel it through the water. As the larva grows, it becomes more similar to an adult sponge and loses its ability to swim. Q: Unlike an adult sponge, what stage is motile due to cilia that propel it through water? Choices: - parasite - zygote - pupa - larva A:
A: larva