Ch. 17: Physical Changes Vocabulary: physical change, texture, physical property, dissolve, matter, state of matter, solid, liquid, gas, melt, evaporate, water vapor, freeze, condense

Changes in Physical Properties The world around you is made of matter that is constantly changing. Matter is all the stuff in the world that takes up space. One of the way that matter changes is through physical changes. Physical changes are changes in which no new materials are formed.

Changes in Physical Properties Physical Changes Size Color Smell Weight State (solid, liquid, gas) Shape Texture Temperature Hardness Cutting Warming Melting Evaporating Boiling Bending Cooling Freezing Condensing Dissolving Physical changes are affected when you change a physical property. Physical properties are the features of objects that you can observe directly, or with a tool.

Changes in Physical Properties For example: One of the ways you can affect a physical change is by changing an objects texture. Texture is the way a surface feels. Some objects like clay, you can change the texture of. You can make clay either smooth or rough depending on how you mold it.

Changes in Physical Properties Another example: Another physical property of materials is whether or not it dissolves in water. Dissolve means to mix evenly in a liquid. When materials dissolve, they seem to disappear, but you can tell they are still there. Both sugar and salt dissolve in water, but you definitely can tell what water has salt dissolved into it compared to the water with sugar dissolved in it based on the taste.

Changes in Physical Properties Remember, physical changes can be reversed. If you make clay rough, you can smooth it back out. If you dissolve salt in water, you can evaporate the water and see the salt in the glass again.

Changes in State Another way matter can change is through a change in state. Matter can exist in three different forms. It can be in solid form, in liquid form, or in gas form. Solids keep their own shape. Liquids take the shape of the container that they are placed in. Gasses spread out in all directions as far as they can.

Changes in State By looking at the state each part of matter is in, you can tell what the atoms in that matter are doing. Atoms are the tiny building blocks that make up everything (even cells are made of atoms.) The atoms in solids don’t move around very much, they stay grouped together. The atoms in liquids kind of stay together, but they move around and push against each other. The atoms in gasses try to get as far away from each other as possible. Solid Liquid Gas

Changes in State Matter usually changes state when you raise or lower its temperature. When heat is added, the atoms in matter move around more. So when heat is added to solids it makes the atoms move which turns it into a liquid (melting.) When more heat is added the atoms move around even more turning the matter into a gas (evaporation.) When heat is removed from a gas, it makes the atoms slow down and turn back into a liquid (condensation.) When more heat is removed from the liquid the atoms move even less, turning it into a solid (freezing.)

Changes in State ICE LIQUID WATER WATER VAPOR

Question About Chapter 17 Describe what happens when you stir sugar into a hot cup of tea. Describe how you can you two different kinds of reverse physical changes. What happens to the atoms in a substance when it freezes? What happens to the atoms in a substance when it melts? What does it mean when something condenses? What does it mean when something evaporates? In which state of matter are the atoms in it the farthest apart?