Why do liquids pour

Nature of science Things can be done to materials to change some of their properties, but not all materials respond in the same way. Go to full glossary Add 0 items to collection. Download 0 items. Twitter Pinterest Facebook Instagram. Email Us. See our newsletters here. Would you like to take a short survey?

This survey will open in a new tab and you can fill it out after your visit to the site. These are all made up of tiny particles but the strength by which they connect to one another differs.

In solids these particles hold on to one another tightly. For liquids and gases these particles can flow over or alongside one another. That is why liquids and gases are also called fluids: because they can flow.

This flow can be smooth, chaotic or anything in between. A smooth flow is called laminar and its opposite is called a turbulent.

When you pour fluid out of a container you remove particles from that container leaving space behind. One of two things can happen as a result: The container can collapse and become smaller or another fluid can rush in and fill the emptiness. This happens because the tiny particles that make up a fluid press against everything around them.

As long as the particles inside the container press about as hard as the particles on the outside, the container will hold its form. If fluid flows out, there are suddenly many fewer particles pressing on the inside of the container while the pressure on the outside remains constant. As a result, the container might collapse. In other circumstances another fluid will rush in, fill the space and help press against the inner walls so the inside and outside pressures equalize again.

This activity explores the different ways a fluid can flow in while you pour water—and how that can affect the flow. Observations and results Did the water flow the smoothest when you held the box on side panel C?

Did it flow most turbulently when your hand covered part of side panel A? Maybe you even developed a new preference. Preferences are personal choices and can differ from person to person. Laws of physics, by contrast, determine how the water flows.

You might think the box was empty when you poured all the water out, but it was not. Something else filled the box—something you cannot see: air. If liquid is poured out, another fluid such as air will take its place or the container will collapse. Unless you take very special measures, the empty space created by pouring out water does not stay empty for long!

In your case the container probably held its form and air rushed in. Sometimes air can flow in and water can pour out simultaneously. The two flow alongside each other, resulting in fluent or laminar flows. You probably saw this when you poured while gripping side panel C.

Holding the box by this side allows you to tilt the box quite far before the water level reaches the spout. This makes it easier to create a nice stream of water without filling the spout opening entirely, leaving space for air to flow in while water pours out.

When you poured while holding side panel A, a much smaller tilt of the box made the water pour out but it almost instantly covered the spout completely, leaving no room for air to flow in. Geological Survey.

Cohesive forces are greatest beneath the surface of the liquid, where the particles are attracted to each other on all sides. Particles at the surface are more strongly attracted to the identical particles within the liquid than they are to the surrounding air.

This accounts for the tendency of liquids to form spheres, the shape with the least amount of surface area. When these liquid spheres are distorted by gravity, they form the classic raindrop shape. Adhesion is when forces of attraction exist between different types of particles.

Particles of a liquid will not only be attracted to one another, but they are generally attracted to the particles that make up the container holding the liquid. Particles of the liquid are drawn up above the surface level of the liquid at the edges where they are in contact with the sides of the container.

The combination of cohesive and adhesive forces means that a slight concave curve, known as the meniscus, exists at the surface of most liquids.

The most accurate measurement of the volume of a liquid in a graduated cylinder will be observed by looking at the volume marks closest to the bottom of this meniscus. Adhesion also accounts for capillary action when a liquid is drawn up into a very narrow tube. One example of capillary action is when someone collects a sample of blood by touching a tiny glass tube to the blood droplet on the tip of a pricked finger. Viscosity is a measure of how much a liquid resists flowing freely.

A liquid that flows very slowly is said to be more viscous than a liquid that flows easily and quickly. A substance with low viscosity is considered to be thinner than a substance with higher viscosity, which is usually thought of as being thicker.

For example, honey is more viscous than water.