Milk is a kind of liquid. A liquid doesn't have its own shape. It has the shape of the container it is in. The milk shown here has taken the shape of the glass.
Click on image for full size
Image courtesy of Corel Corporation.
Liquid is one of the four common states of matter. The three others are gas, solid, and plasma. There are also some other exotic states of matter that have been discovered in recent years.
A liquid does not have a fixed shape, like a solid; instead it takes on the shape of the container that it is in. Liquids can flow. A liquid has a distinct surface, unlike a gas. This surface is called a free surface. For example, water in a glass has a surface where the water ends and the air above it begins.
When a liquid boils or evaporates, it becomes a gas. When a liquid freezes, it becomes a solid. For example, when liquid water boils, it becomes water vapor. When liquid water freezes, it becomes ice.
In everyday life we think of a liquid and a fluid as being the same thing. Scientists use the term "fluid" in a special way, though, to mean things that can flow. Liquids, gases, and plasmas are all fluids as far as scientists are concerned.
Water is probably what you think of when someone mentions a liquid. Milk, gasoline, and cooking oil are other common liquids. Some common substances, like the oxygen and nitrogen in air, are gases under "normal" circumstances but can become liquids if they are very, very cold. Mercury is a kind of metal that is a liquid at normal temperatures; it doesn't "freeze" and become a solid until cooled to -39° C (-38° F). Glass and steel become liquids when they are heated to very, very high temperatures.
Shop Windows to the Universe Science Store!
Our online store
on science education, ranging from evolution
, classroom research
, and the need for science and math literacy
You might also be interested in:
Solid is one of the four common states of matter. The three others are gas, liquid, and plasma. There are also some other exotic states of matter that have been discovered in recent years. Unlike liquids...more
Plasma is known as the fourth state of matter. The other three states are solid, liquid and gas.Almost everything is made up of atoms (your dog, your science book, this computer...). The atom has a nucleus...more
A snowman, glass of water and steam might look very different but they are made of the same stuff! Just like any substance, water has three different forms, called states: solid, liquid and gas. The state...more
Have you ever left a glass of water out for a long time? Did you notice that the water disappears after a few days? That's because it evaporated! Evaporation is when water passes from a liquid to a gas....more
Frozen water is found in many different places on Earth. Snow blankets the ground at mid and high latitudes during winter. Sea ice and icebergs float in the chilly waters of polar oceans. Ice shelves are...more
Oxygen (O2) is a kind of gas. A lot of the air you breathe is oxygen. That's a good thing, since we need oxygen to stay alive! About 4/5ths of the air in Earth's atmosphere is nitrogen (N2). Almost all...more
There is more nitrogen gas in the air than any other kind of gas. About four out of five of the molecules in Earth's atmosphere is nitrogen gas! A molecule of nitrogen gas is made up of two nitrogen atoms....more