Solids, Liquids, and Gasses

Solids, liquids, and gasses Important Ideas ➢ The study of matter is called chemistry. ➢ Atoms and molecules are the minuscule building blocks of matter. ➢ The three common states of matter on Earth are gases, liquids, and solids, which are composed of atoms and molecules. ➢ Liquid particles are in motion, attracted to one another, and capable of passing one another. ➢ What makes a substance a solid, liquid, or gas is one of its properties. Chemistry is ... The study of matter and what matter does. In other words... The study of stuff and what stuff does on a very small scale Water • Is a good example of a molecule, and molecules are made of atoms Definition What are atoms? Atoms are the basic building blocks of matter that make up everyday objects. A desk, the air, even you are made up of atoms! There are 90 naturally occurring kinds of atoms. Scientists in labs have been able to make about 25 more. Bill Nye on Atoms Make a venn diagram for atoms and molecules: Definition A molecule is an electrically neutral group of two or more atoms held together by chemical bonds • • Why do you think the water keeps its shape the moment the balloon is popped? Imagine a drop of water hanging from your finger. How is this similar to the water staying together after the balloon is popped? Watch supercooled water Then what are elements? Definition: a pure chemical substance consisting of a single type of atom Molecules in Motion • • • • Heating a liquid increases the speed of the molecules. An increase in the speed of the molecules competes with the attraction between molecules and causes molecules to move a little further apart. Cooling a liquid decreases the speed of the molecules. A decrease in the speed of the molecules allows the attractions between molecules to bring them a little closer together. Molecules... move faster as (heat) energy is added to the system. Design an experiment that proves that hot water molecules are moving faster than cold water molecules Observation: Molecules are in constant motion and move faster as heat is added. Hypothesis: If I add heat to water then the molecules will move faster Experiment: Use water, food coloring, and glassware to design your experiment. How does this cause changes in state? • • • • Heating a substance increases molecular motion. Cooling a substance decreases molecular motion. As molecular motion increases, the space between molecules increases. As molecular motion decreases, the space between molecules decreases. Cold Water Would the water molecules be closer together or further apart? Would there be more or fewer motion lines? Hot Water • • • Would the water molecules be closer together or further apart? Would there be more or fewer motion lines? What evidence do you have from your experiment to show that the speed of the water molecules is different in hot water? Let’s say that you measure exactly 100 milliliters of water in a graduated cylinder. You heat the water to 100 °C and notice that the volume increases to 104 milliliters. Using what you know about the attractions between water molecules and the way heat affects molecular motion, explain why the volume of water in the cylinder increases when it is heated. Moving Molecules in a solid Key Concepts ➢ In a solid, the atoms are very attracted to one another. The atoms vibrate but stay in fixed positions because of their strong attractions for one another. ➢ Heating a solid increases the motion of the atoms. ➢ An increase in the motion of the atoms competes with the attraction between atoms and causes them to move a little further apart. Cooling a solid decreases the motion of the atoms. A decrease in the motion of the atoms allows the attractions between atoms to bring them a little close together. How can you describe them if you didn't know what they were? • • • Describing objects by using size shape • • • color texture uses an object's properties. Physical properties • • • • • • • Physical properties can be observed or measured without changing the identity of the matter. Basically, properties you notice when using one of your five senses: Feel - mass, volume, texture Sight - color Hear Smell Taste Physical properties of matter are categorized as either: Intensive or Extensive: • • • • • • • • • • Intensive - Properties that do not depend on the amount of the matter present. Color Odor Luster - How shiny a substance is. Malleability - The ability of a substance to be beaten into thin sheets. Ductility - The ability of a substance to be drawn into thin wires. Conductivity - The ability of a substance to allow the flow of energy or electricity. Hardness - How easily a substance can be scratched. Melting/Freezing Point The temperature at which the solid and liquid phases of a substance are in equilibrium at atmospheric pressure. Boiling Point - The temperature at which the vapor pressure of a liquid is equal to the pressure on the liquid (generally atmospheric pressure). More Physical Properties Density is a very important property. • • It is the amount of matter in a given volume. Density = M/ V Mass / Volume Properties of all objects • • • • Objects take up space. All objects take up space. Your computer is taking up space on the desk. You are taking up space on the chair. Properties of Matter • A property describes how an object looks, feels, or acts. Properties are constantly changing... • • • • Matter is constantly changing. Ice in your soda melts, glass breaks, paper is ripped. When ice in your soda melts where does it go? What does it become? Physical vs. Chemical • • • Physical properties: observe without changing the identity of the substance Chemical properties: observe only when the identity changes How do you know if it is chemical or physical? ▪ If it CHanges, it’s Chemical Chemical properties • • A common chemical property is reactivity. ▪ Reactive to oxygen ▪ Reactive to air ▪ Reactive to water… Notice that chemical properties aren’t EASY to observe, unlike physical properties. Physical Changes: • • • Changes in matter that do not alter the identity of the matter itself. Changes that do NOT change the identity of the substance. You may or may not be able to undo a physical change. For example: • • • • • • • Size Shape State - solid liquid gas Dilutions The water doesn't turn into soil or macaroni. It remains water. If it did change into soil or macaroni, your drink would taste terrible and you would have an example of a chemical change Chemical change • • • Chemical changes do alter the identity of a substance In other words, a chemical change is when something changes into an entirely different substance For example: ▪ Iron rusting ▪ Wood burning ▪ Copper turning to brass ▪ Baking a cake ▪ spoiled milk Chemical properties: • • • • These are properties that can only be observed by changing the identity of the substance. A piece of paper burns and turns to a black substance. After the flame goes out you can no longer burn the new substance. The chemical properties Common Errors • • • *Ice melting, water freezing, water evaporating, and steam condensing are all examples of a state change. *These are physical changes, not chemical. *Diluting a solution is a physical change, even if the color becomes more faint. Energy • • Like conservation of matter states that matter can’t be created or destroyed…. Conservation of energy means that energy can’t be created or destroyed Some types of energy • Kinetic: energy of motion Potential • Energy of position Chemical • A form of potential energy stored in the bonds between molecules Electromagnetic • A form of kinetic energy, found I the form of waves. For example, light waves, sound waves, radio waves, etc. Electrical • The energy of moving electrons Review: What do you know about the molecules in a liquid? How does heating or cooling affect the speed of the molecules and the distance between them? Do you think the atoms in a solid are attracted to each other? Do you think heating or cooling a solid might affect the motion of the atoms? In a solid... • • • The particles (atoms or molecules) are attracted to each other. The particles (atoms or molecules) vibrate but do not move past one another. The solid retains its shape. Compare the particles in a liquid to the particles in a solid • • The atoms in a solid are so attracted to each other that they vibrate and don’t move past each other. The molecules of a liquid are attracted to each other, but move more freely and past one another. Why won’t the ball fit through the ring? the speed of the atoms in the metal ball has increased. This increased motion competes with the attractions the atoms have for each other, causing the atoms to move slightly further apart. This is why the heated ball is too big to fit through the ring. Many People think the size of the particles get bigger: WRONG! It’s the space between the particles that is bigger Use what you have learned ... - to describe why bridges must have flexible connections Key Concepts • • • • • In a gas, the molecules have very weak attractions for one another. Molecules are able to move freely past each other with little interaction between them. The molecules of a gas are much more spread out and move independently compared to the molecules of liquids and solids. Whether a substance is a solid, liquid, or gas at a certain temperature depends on the balance between the motion of the atoms or molecules at that temperature and how strong their attractions are for one another. Heating a gas increases the speed of its molecules. Cooling a gas decreases the speed of its molecules. Since gasses are matter... They behave like solids and liquids when energy (heat) is added or taken away. Evidence that gases expand when heated Review: Behaviors of solids, liquids, and gasses as you add or remove heat. Solid • • • • Molecules are very attracted to one another. Molecules vibrate but do not move past one another. The molecules stay in fixed positions because of their strong attractions for one another. A solid has a definite volume and a definite shape. Liquid • • • Molecules are attracted to one another. Molecules vibrate but are also able to move past one another. A liquid has a definite volume but does not have a definite shape. Gas • • • • Molecules are not attracted to each other much at all. Molecules vibrate and are also able to move freely past each other. A gas does not have a definite shape or volume. Gas molecules will spread out evenly to fill any container. Imagine what a tablespoon of water looks like. If that same number of molecules was a gas, they would be spread out enough to fill up a whole beach ball. The molecules that make up a gas are about 100 to 1000 times further apart than the molecules of a solid or liquid. At room temperature they are moving at about 1000 miles per hour, but over very short distances.