The Properties and Changes of Matter

Section 1 Physical Properties

Physical Properties and Changes When you look into your wallet, guess what, it is EMPTY! You need money but none is coming any time soon You decide it is time to get a job. You find a job at a grocery store that is getting ready to make its grand opening Your first job is to make decisions on where things go. What do you do first? First you should make observations What can you see, hear, taste, smell, and touch

Physical Properties and Changes Whether in a new job or a laboratory, you use your senses to observe materials. Any Characteristic that can be observed or measured without changing the identity of the material is a physical property. WARNING: you should never touch, smell, or taste anything in the lab without guidance.

Physical Properties Your first assignment of your new job is to give input on how to arrange a list of items in the store. You decide to go make some observations about the items you will be arranging. One of the key senses in making physical observations is sight Everything you can see, touch, smell, or taste is matter. Matter is anything that has mass and take up space You could arrange items with similar color packaging together, or perhaps similar shape packaging

Physical Properties As you arrange the laundry detergent in the store, you notice many of the bottles are made of plastic When that plastic is molded to make the bottle, it changes its shape, but it is still plastic This type of change is a physical change A physical change is when the properties of a substance change, but the identity of the substance does not change

Length and Mass Some physical properties can be observed, while others can be measured. One useful measureable property is length. Length can be measured using a ruler, meter stick, or tape measure. Maybe you decide to order the French bread in the store by length. Another physical property that can be measured is mass - a physical property that describes the amount of material in an object. You notice that some of the boxes of detergent are heavier than others. The detergent did not change, just the size of the box. This is an example of mass

Volume and Density Mass isn’t the only measurement that describes how much of something there is. Volume measures the amount of space something takes up Liquids are usually measured by volume, so you could arrange your juices by volume Another measurement related to mass and volume is density Density measures how much mass a material has for a given volume Density is found using the formula D=m/V or Density equals mass divided by volume

Same Volume, Different Mass Try lifting a bowling ball and a Volleyball. Which would be heavier and therefore, more dense? Customers at your store would notice different densities if you loaded all the canned goods in one bag, while putting all the napkins and cereal in the other. Density stays the same as long as temperature and pressure stay the same Water at room temperature has a density of 1.00 g/cm3, while ice has a density of .9168 g/cm3. Has the identity of water changed, no, but something has changed

States of Matter When water goes from 20oC to 0oC, it changes from a liquid to a solid. There are 4 states of matter, solid, liquid, gas, and plasma The state of matter of a substance depend on temperature and pressure While you experience 3 of the states of matter on a daily basis, plasma occurs only at very high temperatures such as in fluorescent lightbulbs, the atmosphere, and lightning strikes

Moving Particles Matter is made up of moving particles. The amount of energy those particles have determine the state of matter. Particles in a solid vibrate in a fixed position and therefore give the solid definite shape and volume Particles in a liquid move much faster and have the energy to move past one another, giving the object a definite volume but allows it to take the shape of its container Particles in a gas move so freely, they can move away from other objects. Gases will take up as much space as possible meaning they no definite shape or volume

Bellringer What are the four states of matter? Which state of matter has so much energy that the molecules spread out as much as possible? Which is more dense, a brick or a loaf of bread? Melting ice is an example of what kind of change? Which state of matter only happens at extremely high temperatures?

Changes of State When you put ice into water it melts, you still have water, just in another state. As part of your job at the store, you will need to make decisions based on the ability of objects to changes states. You do not want the frozen foods turning into a slushy liquid and you don’t want other liquids to freeze The temperature at which a solid becomes a liquid is its melting point. The temperature at which a liquid becomes a gas is its boiling point. The melting point nor boiling point change based on how much of the substance there is, water will always melt at 0oC and boil at 100oC The boiling point and melting point can help us identify a substance, if it boils at 56.1oC, it can not be water since water boils at 100oC.

Metallic Properties Certain physical properties allows you to classify things as metal Have you noticed how metals are shiny. This shine is called luster Metals also have the ability to be hammered or rolled into sheets. This property of metal is called malleability Metal can also be drawn into thin wires. This is called ductility. Many metals can also respond to the force of magnets These properties can be useful at your store because you know your shiny, new carts can be dented because they are malleable and that magnets can be used to hang sale papers.

Substances Matter can be classified by its physical properties One way is to classify something by its chemical composition. Matter that has the same composition and properties throughout is called a substance There are two types of substances – elements and compounds Substances made of only one kind of atom are called elements – they can not be broken down into simpler substances by physical or chemical means Different elements can combine to create new substances called compounds. These compounds can be broken down by physical or chemical means Gold is and Element Bronze is a compound made of tin and copper

Mixtures When two or more substances combine but do not chemically combine or bond to make a new substance, a mixture results You can add dry sand to a bucket of water to make a mixture, you can add more sand or more water but you still have mud. Physical properties can be used to separate the mixture into simpler substances such as pouring the mixture through a sieve to separate the solids from the liquids

Mixtures There are two kinds of mixtures, homogenous and heterogeneous mixtures Homogenous mixtures – meaning the same throughout, these mixtures are mixed evenly so you cant tell the individual pieces that make up the mixture You can’t see the zinc and copper used to make brass trumpets, or the oxygen, neon, argon, helium, carbon dioxide, and water that makes up the air we breathe Heterogeneous mixtures are not evenly mixed and it is easy to see the individual parts that make up the mixture You can easily see the individual toppings that make up a pizza or the ingredients that make up a salad

Section 2 Chemical Properties

Chemical Properties After successfully stocking the store shelves, the manager decides to take the group on a campout with a bonfire to celebrate All of the properties we looked at in the first section were physical changes, but something different appears to happen when the fire burns Some properties indicate that a change of identity has occurred A chemical property is any characteristic that gives a substance the ability to undergo a change that results in a new substance

Chemical Changes Common chemical properties that substances may have include flammability or the ability to react with electricity, oxygen, light, or water. When these substances combine to create a new substance, this is a chemical change. When wood burns, it combines with oxygen to create gas, smoke, and ash. When iron combines with air it creates the a new substance called rust.

Chemical Changes Did you ever notice that vitamins come in dark colored bottles, that is because some of the ingredients can combine with light to create a change Limestone can be heated to create lime and carbon dioxide, apples when exposed to air turn brown, electricity can be used to separate the oxygen and hydrogen atoms that make water. The important thing to understand is that when a substance goes through a chemical change, it has created a new substance. If a chemical change has occurred, the new substance CAN NOT go back to what it was

Conservation of Mass When you burned that pile of wood at the campfire, you started with many kilograms of wood, but end up with just a few kilograms of ash. It seems as though you lost a lot of mass, the amount of ash does not equal the mass of the starting amount of fire wood. However, when you burned the wood, smoke was created that escaped into the air If you were to capture all of the smoke and ash put out by the fire, it would equal the mass of all of the starting fire wood and oxygen burned in the fire.

Conservation of Mass The law of conservation of mass states that the mass of what you end up with is always the same as what you start with. Mass is neither created nor destroyed during any chemical change, it simply changes to a new substance. When you bake a cake, many ingredients are mixed together, but the cake does not weigh the same as the starting ingredients. That is because during the baking process, some water turned to a gas and escaped into the air If this gas were captured, and weighed with the cake, it would equal the original mass of the ingredients