Chemistry Assessment 2 Material PDF

EXPLORATION 2 Properties of Matter Everything around you—your desk, your chair, and even the people—are all made of...

EXPLORATION 2 Properties of Matter Everything around you—your desk, your chair, and even the people—are all made of matter. Even things you cannot see, such as air, are made of matter. Matter is anything that takes up space and has mass. The mass of an object is the amount of matter the object contains. Although all things are made of matter, the kind and amount of matter in each object usually varies. FIGURE 1: A ball of clay is manipulated into different shapes in each of the images below. The particles of a gas are very far Density is the amount of mass per The starting substances are apart and move rapidly compared to volume of a substance. the (reactants) Tthe new particles in solids or liquids. true substances formed are the True (products) Every substance has unique physical Gas is the most common state of properties that help to distinguish it matter in the universe. from other substances. False Because no atoms are true gained or lost during the In general, the volume of a liquid or chemical reaction, the total The particles in a gas are packed closely solid decreases greatly when it together and have a fixed arrangement. mass of the substances forms a gas. They are widely spaced and move freely. involved ——— False false - sometimes increases and then decreases. ANALYZE The particles that make up aDo the amounts During liquid of massa and matter in Figure 1 change as the size change in state, the physical and shape then increases. decreases, move more rapidlyof the thanclay ballinisachanged? Explain those your reasoning. properties of a substance do not always increases solid do. change, but the chemical composition remains the same. True do. false © Houghton Mifflin Harcourt Publishing Company Image Credits: (all) ©HMH The law of conservation of matter, or the law of conservation of mass, states that matter cannot be created or destroyed in either physical or chemical changes. During a chemical reaction, substances interact with each other to form new substances. The starting substances are the reactants; the new substances formed are the products. The reactant particles are rearranged to form the product particles in such a way that no atoms are lost and no atoms are added. Because no atoms are gained or lost during the chemical reaction, the total mass of the substances involved remains the same. Now consider a spoonful of sodium chloride, also known as table salt. Sodium chloride is made when an atom of sodium bonds to an atom of chlorine. The spoonful of sodium chloride has a specific mass. You can change the total mass by adding salt to the spoon or removing salt from the spoon. The law of EXPLAIN Youconservation pour a spoonfulofofmatter, salt into or theof a glass law of conservation water. of mass, Explain what happens states to the that: mass of the salt and the mass of the water. matter can be created but not destroyed in either physical or chemical changes. matter can be created or destroyed in either physical or chemical changes. matter cannot be created but destroyed in either physical or chemical changes. - matter cannot be created or destroyed in either physical or chemical changes. Lesson 1 Exploring Matter 9  Physical Properties and Physical Changes Every substance has physical properties that help determine its identity. Knowing the properties of a substance is important when chemists choose the best material for a specific use. A physical property is a property that can be measured or observed without changing the identity of matter. Some physical properties are shown in Figure 2. FIGURE 2: Examples of some common physical properties of matter Explore Online Density, melting point, boiling point These may all be classified as the type of property shown in this diagram is: chemical properties physical properties Change of state Properties that can be measured or Corrosive Ice Melting observed without matter changing to an a Density is the amount b Conductivity is a c Malleability is the ability d Solubility is the amount entirely a different substance. of mass per volume of a Conductivity measure of the amount of a substance to be of a substance that substance. of electricity, heat, or flattened. can dissolve in a given plasma sound that a substance Malleability amount of another can carry. substance. physical property physical change Collaborate With a partner, make a list of the physical properties shown in Figure 2. List questions you have about these physical properties. What other characteristics of matter do you think are physical properties? © Houghton Mifflin Harcourt Publishing Company Image Credits: (tl) ©Richard Megna/Fundamental A physical change is a change of matter from one form to another without a change in Photographs; (tcl) ©George Resch/Fundamental Photographs; (tr) ©Chip Clark/Fundamental chemical properties. For example, sugar is soluble in water. When you drink the water, you can taste the sugar although you cannot see it. That is because in the water, the sugar is still sugar. Its identity has not changed. Using Physical Properties to Identify Matter Imagine you have two cups filled with colorless liquids. One cup contains water, and the other cup contains isopropanol, a common component of rubbing alcohol. To differentiate the liquids, you can study some of their physical properties. Property Water Isopropanol Boiling point 100 °C 82 °C 3 3 Density 1.0 g/cm 0.79 g/cm Photographs Conductivity poor poor ANALYZE Which properties would be helpful in determining the identity of the liquids, and which would not be helpful? Explain your answer. 10 Unit 1 Introduction to Chemistry and Engineering  States of Matter FIGURE 3: Water changes state States of matter—solid, liquid, gas, or plasma—are the common forms in from solid (ice) to liquid (liquid which matter exists in the universe. When a substance goes from one state water) to gas (water vapor). of matter to another, the process is called a change in state. During a change in state, the physical properties of a substance change, but the chemical composition does not. When water in the form of ice melts, it looks different on the macroscopic scale, but its chemical composition has not changed on the molecular scale. The What ASK ability of matter questions toyou could conduct electric ask about current or the arrangement heat in the of particles states of matter shown in Figure 3? Mass - Conductivity - Solubility - Malliability The particles in a solid are packed very closely together in a rigid, orderly arrangement. They are held together by the attractive forces that act between all particles of matter. Solids, therefore, have fixed volumes and shapes. In the solid state, particles cannot break away from their fixed position; they can only vibrate in place. The particles that make up a liquid move more rapidly than those in a solid do. This causes the particles in the liquid to overcome some of the attractive forces between them, and the particles can slide freely around each other. The particles of a gas are very far apart and move rapidly compared to particles in solids or liquids. At these distances, the attractive forces between gas particles have a lesser effect than they have on particles in liquids and solids. In general, the volume of a liquid or solid increases greatly when it forms a gas. However, the density of the gaseous state of most substances is approximately one-thousandth the density of the liquid state. © Houghton Mifflin Harcourt Publishing Company Image Credits: ©Richard Megna/Fundamental Plasma is a gas in which the particles have so much energy that they become electrically charged. Plasma is the most common state of matter in the universe, with more than 99.99% of observable matter in the universe being plasma. Most of the matter of the sun is plasma. Stars and lightning are also examples of plasma. However, this state is not experienced in the physical and chemical changes we encounter every day on Earth. MODEL Draw a diagram of the arrangement of water molecules when water is a solid, a liquid, and a gas. Photographs Lesson 1 Exploring Matter 11  Energy and Matter Bose-Einstein Condensate A fifth state of matter, a Bose-Einstein condensate (BEC), was identified by scientists in 1995. In this state, extremely cold particles just above absolute zero (–273 °C or 0 K) barely move. BEC particles have so little energy that they clump and behave as a single particle. Satyendra Nath Bose and Albert Einstein predicted the BEC in the 1920s, but the technology needed to produce the matter did not exist until 1995. Collaborate With a partner, discuss how the matter in a BEC is different from other states of matter. Chemical Properties and Chemical Changes A chemical property is a property that can be determined by attempting to change the identity of a substance, but it cannot be determined simply by observing the substance. Rather, a change (or lack of a change) in a substance must be observed during or after a chemical reaction. Explore Online FIGURE 4: The alkali metals lithium, sodium, and potassium react with water. © Houghton Mifflin Harcourt Publishing Company Image Credits: (all) ©HMH a lithium b sodium c potassium In a chemical change, the particles of a substance are rearranged, resulting in a change in chemical composition. Figure 4 shows three metals—lithium, sodium, and potassium— each reacting with water. The products of the reactions include hydrogen gas, which can burn if the reactions take place in the presence of oxygen. The reactivity of alkali metals with water is a chemical property. This property cannot be observed until the metal and water react and both the metal and the water change identity in the process. Rusting is also a chemical change. Iron oxide, or rust, forms when iron is exposed to water and oxygen. Understanding the chemical properties of matter is critical for safety when using materials such as the rechargeable lithium batteries found in laptop computers. ANALYZE Classify each statement as describing a chemical or a physical change. Explain your reasoning. A piece of metal melts. A piece of coal burns. An egg cooks on a stove. 12 Unit 1 Introduction to Chemistry and Engineering  Using Chemical Properties to Identify Matter Chemical properties can also be used to identify a substance and they determine which kinds of materials a substance will react with. An example of a chemical property is flammability, or the ability of a substance to catch on fire. Water is not flammable, but isopropanol is. Another chemical property, reactivity, describes how likely a substance is to undergo a chemical reaction. Acidity is another chemical property. Some strong acids, such as hydrochloric acid, are highly corrosive. EVALUATE You have two samples of gray powder, both of which are flammable. Are these powders the same substance? Explain your reasoning. Extensive and Intensive Properties Scientists describe properties of matter as extensive and intensive. An extensive property depends directly on the amount of the substance present. An intensive property is one that does not depend on the amount of the substance present. For any particular substance, any amount of the substance has the same value for any intensive property. APPLY Classify each statement as an extensive or an intensive property. A pot of boiling water has more energy than a cup of boiling water. extensive | intensive A big piece of metal melts at the same temperature as a small piece. extensive | intensive Copper wire conducts electricity. extensive | intensive As seen in Figure 5, if you put a 12-ounce can of regular cola and a 12-ounce can of diet cola in a tub of water, you will notice the regular cola sinks and the diet cola floats. The sweetener in diet cola is hundreds of times sweeter per unit volume than the sugar in regular cola. © Houghton Mifflin Harcourt Publishing Company Image Credits: ©HMH EXPLAIN Why does the can of diet cola float in water but the can of regular FIGURE 5: Cans of regular cola does not? Consider mass and density in your explanation. cola and diet cola behave differently in water. Collaborate With a partner, list the extensive and intensive properties described in the cola experiment. Which properties would change and which would stay the same if you ran the experiment using 7.5-ounce cans instead? Evidence Notebook Which physical and chemical properties would allow you to determine if a new material can replace an existing material? For example, what properties must a plastic pipe have in order to perform the same function as a metal pipe? Lesson 1 Exploring Matter 13