Energy and Matter

Lesson Objectives

• I can explain movement of particles in the different states/phases of matter.

Introduction

Why do different states of matter have different properties? The tiny particles that make up matter, called atoms and molecules, are affected by energy. The amount of energy the particles have determines how fast these particles move and how tightly connected they are.

Guided Learning

Energy

Energy is defined as the ability to cause changes in matter. You can change energy from one form to another when you lift your arm or take a step. In each case, energy is used to move matter — you.

These three states of matter are common on Earth. What are some substances that usually exist in each of these states?

States of Matter

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In solids, the particles are packed closely together and cannot move around. All they can do is vibrate. This explains why solids have a fixed volume and shape. The particles are constantly moving but very slowly which maintains a very strong bond among the particles.

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In liquids, the particles can slide past one another but not pull completely apart. This explains why liquids can change shape but have a fixed volume. The particles are moving more rapidly than in solids and the particles maintain a strong bond but not as strong as that of solids.

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In gases, the particles can completely overcome the force of attraction between them and move apart. This explains why gases have neither a fixed volume nor a fixed shape. The particles are moving extremely fast and lose their bond with other particles.

Remember when we talked about the way molecules move in the different phase of matter? We mentioned that the speed of movement of molecules is different in each of the phases because of the amount of energy contained in the particles. Later, we will talk about how these affect evaporation, condensation, and freezing.

Solids = molecules move slowly and are tightly connected with little space in between molecules

Liquids = molecules move more rapidly and are loosely connected with moderate space between molecules

Gases = molecules move very rapidly and are very loosely connected with a great deal of space between molecules

This is important to remember because thermal expansion, contraction, and compression all depend on the spacing between molecules of a given object which is directly affected by the amount of energy contained in the particles.

Will it all fit?^[4]

When we pack to go on vacation, there is always “one more” thing that we need to get in the suitcase. Maybe it’s another bathing suit, pair of shoes, book – whatever the item, we need to get it in. Fortunately, we can squeeze things together somewhat. There is a little space between the folds of clothing, we can rearrange the shoes, and somehow we get that last thing in and close the suitcase. This is what we call compression.

Compression

Have you ever tried to squeeze a balloon? If you have, you know that the balloon changes shape depending on where you put pressure. This is what we call compression. We can compress air very easily, because it is a gas and the molecules are very loosely connected which means that gases can occupy large areas. As we have learned, the molecules of gas are spread out giving it low density which makes it easy for us to squeeze into smaller spaces. It would be very different if we tried to squeeze a balloon full of water, wouldn’t it? What do you think would happen to the balloon? Water is more dense and therefore cannot be compressed as easily. Because the particles of a solid are already very closely packed together, compressing a solid is very difficult. Think of a book you have read. What would happen if you tried to squeeze the book? Would it occupy a smaller space?

Compressibility is the measure of how much a given volume of matter decreases when placed under pressure. If we put pressure on a solid or a liquid, there is essentially no change in volume because the particles are already so closely packed together.

Learn more about expansion and contraction with this five-minute video.

Expansion and Contraction^[5]

Thermal Expansion occurs when the volume of a substance is increased by adding energy in the form of heat. The added energy causes the particles to move quickly and spread apart. Contraction occurs when there is a decrease in volume due to a loss of energy in the form of heat. As a substance cools or loses heat, the particles move less quickly which causes them to move closer together.

Before the digital thermometer was invented, thermometers were made of glass and contained liquid mercury inside of the tube. The change in temperature would expand the liquid which then caused the liquid to rise in the tube allowing for the measurement of temperature. Mercury was later discovered to be poisonous and alcohol was used instead.

If you’ve ever watched popcorn pop, you’ve seen another example of thermal expansion. Inside each kernel is a small amount of water. When that water is heated, it causes the expansion of the water which then causes the popcorn kernel to POP!

Review

• Solid molecules move slowly and are tightly connected with little space in between molecules.
• Liquid molecules move more rapidly and are loosely connected with moderate space between molecules.
• Gas molecules move very rapidly and are very loosely connected with a great deal of space between molecules.
• There is no change in volume when pressure is applied to liquids and solids.
• Gases compress more easily than liquids and solids.

Energy        

Energy is defined as the ability to cause changes in matter.

Compression

        Compression is the decrease in volume of a substance due to pressure applied to that substance.

Compressibility  

Compressibility is the measure of how much a given volume of matter decreases when placed        under pressure.

Thermal Expansion

Thermal expansion occurs when the volume of a substance is increased by adding energy in the form of heat.

Contraction  

Contraction occurs when there is a decrease in volume due to a loss of energy in the form of heat.