liquids

water and other liquids

Water is the most common substance on Earth, and most of it exists in the liquid state. A liquid is one of four well-known states of matter, along with solid, gas, and plasma states. The particles of liquids are in close contact with each other but not as tightly packed as the particles in solids. The particles can slip past one another and take the shape of their container. However, they cannot pull apart and spread out to take the volume of their container, as particles of a gas can. If the volume of a liquid is less than the volume of its container, the top surface of the liquid will be exposed to the air, like the vinegar in the bottle pictured in the Figure 1.1. Q: Why does most water on Earths surface exist in a liquid state? In what other states does water exist on Earth? A: Almost 97 percent of water on Earths surface is found as liquid salt water in the oceans. The temperature over most of Earths surface is above the freezing point (0 C) of water, so relatively little water exists as ice. Even near the poles, most of the water in the oceans is above the freezing point. And in very few places on Earths surface do temperatures reach the boiling point (100 C) of water. Although water exists in the atmosphere in a gaseous state, water vapor makes up less than 1 percent of Earths total water.

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surface tension and viscosity

Two unique properties of liquids are surface tension and viscosity. Surface tension is a force that pulls particles at the exposed surface of a liquid toward other liquid particles. Surface tension explains why water forms droplets, like the water droplet that has formed on the leaky faucet pictured in the Figure 1.2. Water drips from a leaky faucet. Viscosity is a liquids resistance to flowing. You can think of it as friction between particles of liquid. Thicker liquids are more viscous than thinner liquids. For example, the honey pictured in the Figure 1.3 is more viscous than the vinegar. Q: Which liquid do you think is more viscous: honey or chocolate syrup?

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instructional diagrams

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questions

particles of a liquid always take the volume of their container.

a. true

-->  b. false

surface tension is the

a) resistance of a liquid to flowing.

-->  b) force that causes water to form droplets.

c) tendency of fluids to flow downhill.

d) friction of particles flowing over a surface.

which of these liquids is most viscous?

a) water

b) milk

c) vinegar

-->  d) honey

surface tension and viscosity are unique properties of liquids.

-->  a. true

b. false

diagram questions

No diagram questions associated with this lesson