Matter

Matter and Particles All matter is made up of tiny particles called atoms and molecules. The state of a substance depends on how fast its particles move and how strong the attraction is.

The Phases of Matter There are FOUR states of matter: Solid – has a definite shape and volume Liquid – has a definite volume but a shape that can change and can flow Gas – has neither a definite shape or volume and can flow Plasma – doesn’t have a definite shape or volume and only exists at high temperatures (stars, sun, etc…)

Solid Particles In a solid, the particles are packed together. They vibrate in place and the attraction between them is strong. This causes the particles to lock together.

Liquid Particles In a liquid, the particles vibrate faster and the attraction isn’t as strong. This allows the particles to flow around and over each other. Liquids assume the shape of their containers. Liquids can also be called “fluid” – which means a “substance that flows.”

Gas Particles In a gas, the particles move fast and overcome the attraction between them and separate from each other entirely. That’s why a gas will spread out in all directions – filling up a balloon, a room, or the atmosphere.

Melting: From Solid to Liquid Melting is the change from a solid state to a liquid state. The temperature at which a solid melts is called its melting point. The melting point is different for different solids. For ice, it is 0oC or 32oF.

Melting and the Particles As you heat a solid, the particles in that solid will begin to move faster. They are absorbing energy! Eventually the motion of the particles will become great enough to overcome the attraction that locks the particles together as a solid. When that happens, the solid becomes a liquid because the particles start to flow.

Freezing: From Liquid to Solid Freezing is the change from a liquid state to a solid state. The temperature at which a liquid freezes is called its freezing point. The freezing point for different solids is different. For water, it is 0oC or 32oF.

Freezing and the Particles If you cool a liquid, the particles will begin to slow down. They are releasing/losing energy! Eventually the motion of the particles will slow to the point where they cannot overcome the attraction between them. When that happens, the particles will lock together and become a solid.

Vaporization: From Liquid to Gas Vaporization is the change from a liquid state to a gaseous state. The temperature at which water changes from a liquid state to a gaseous state is 100oC or 212oF. This is known as its boiling point.

Vaporization and the Particles As a substance is heated, its particles begin to move faster and faster. They are absorbing energy! During vaporization, the fastest particles are able to overcome the attraction of the particles around them and break free completely. These escaped particles become a gas (ex: water vapor).

Vaporization vs. Evaporation Vaporization refers to the phase transition where a substance changes from a liquid to a gas. Evaporation is a specific type of vaporization which occurs at temperatures below the boiling point of a liquid. So vaporization includes evaporation and boiling.

Vaporization vs. Evaporation Evaporation occurs at the liquid’s surface, but vaporization could happen below the surface when a liquid is boiling. Think about water evaporating from a puddle vs water boiling in a pot.

Vaporization: Solid to Gas Sublimation is the change from a solid state to a gas state. This is a result of vapor pressure and temperature relationships. (Examples include dry ice and freeze drying food.)

Condensation: From Gas to Liquid Condensation is the change from a gaseous state to a liquid state. The temperature at which a gas condenses is called its condensation point. For water vapor, it is 100oC or 212oF.

Condensation: From Gas to Liquid If you cool a gas, the particles will begin to slow down. They are releasing/losing energy! Eventually the motion of the particles will slow to the point where they cannot overcome the attraction between them. When that happens, the particles will lock together and become a liquid.

Physical Properties A physical property of matter can be observed or measured without changing the matter’s identity. Some physical properties are color, odor, mass, volume, magnetism, ability to conduct current, strength, flexibility, hardness, and texture. Ex – Will your books fit into you backpack? You are using the physical property of volume.

Physical Properties Thermal conductivity – is the rate at which a substance transfer heat. Ex. Styrofoam is a poor conductor. State of Matter – solid, liquid, or gas (ex: ice, water, water vapor) Density – the mass per unit of volume. (ex: Lead is very dense so it is used to make an anchor.)

Physical Properties Solubility – is the ability of a substance to dissolve in another substance. (ex: Kool-Aid power dissolves is water.) Sometimes you can increase solubility by changing the temperature. Ductility – is the ability of a substance to be pulled into a wire. (ex: Copper is often used to make wiring because it is ductile.) Malleability – is the ability of a substance to be rolled or pounded into thin sheets. (ex: Aluminum can be rolled into sheets to make foil.)

Physical Changes A physical change is a change that affects one or more physical properties of a substance. Ex. A piece of silver is pounded and molded into a heart-shaped pendent. (it is still silver) Ex. – changing from a liquid to a solid (or any phase change) Ex. – crushing an Aluminum can. It is still aluminum, just the shape has changed. Ex – Sawdust – it is still wood – only in smaller pieces.

Chemical Properties Chemical properties describe matter based on its ability to change into new matter that has different properties (in the form of a chemical reaction). Chemical changes occur when bonds break and new bonds form. Ex. – burning wood, tarnishing, and rusting

Chemical Properties Flammability – is the ability of a substance to burn. (wood can burn, but ash and smoke cannot) Reactivity – is the ability of two or more substances to combine and form one or more new substances. Chemical reactions involve two main kinds of changes that you can observe – formation of new substances and changes in energy.

Physical Properties vs. Chemical Properties A nail will bend – physical property being changed is shape A nail will rust – chemical property being changed is composition (iron is reacting with oxygen to make iron oxide - rust) Alcohol will evaporate – physical change of state Alcohol will burn – chemical change – it is not alcohol any more.

How do I know that a chemical change is taking place? There will be a change is odor, color, heat will be either absorbed or released, the substance will bubble or fizz, light or sound may be given off. Ex. Soured milk Alka-Seltzer tablets fizzing Car rusting Cake baking Chemical reaction going on in your body

Changes in Energy As matter changes, it can either absorb or release energy. A change in energy occurs during a chemical reaction. An endothermic reaction is a reaction in which energy is absorbed. Many endothermic reactions occur when heat is constantly added. (Ex: egg frying) In other words…they need energy to keep going.

Changes in Energy An exothermic reaction is a reaction that releases energy in the form of heat. After an exothermic reaction, the products have less energy than the reactants. (Ex: the burning of fuel) The reaction between fuel and oxygen in an airplane engine releases energy, mostly in the form of heat. The expansion and movement of the gases out of the plane exerts a force that moves the plane forward.

Can physical and chemical changes be reversed? Physical changes are easily reversed. You can melt ice and then freeze it again. Chemical changed are not easily reversed. When a firework explodes it would be almost impossible to put the materials back together.