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Name: ___________________________ Period:__ Seat__ Date: _________

Unit-3: Matter—Properties and Changes Unit Introduction

Chemistry is a science that concerns matter and the changes of matter that result from the interactions of matter and energy. The terms matter and energy are familiar to all of us but their definitions, at least within chemistry, are not simple. Let’s look deeper into matter and energy by asking the questions, (1) what is, Energy and (2) what is, Matter.

1. ENERGY: there are many forms of energy and all forms adhere to the law of conservation of energy. Energy is the ability to do work or give off heat.

i. WORK = force on an object applied over a distance ii. HEAT = is related to the movement of atoms or molecules within a substance, its kinetic energy.

• The law of conservation of ENERGY: the total energy of a closed system remains constant or conserved

over time. So, energy can neither be created nor destroyed and it can only be transformed or transferred from one form to another.

Figure-1: Ten forms of energy:

2. MATTER: The visible portion of the universe (5% of the universe) is made up of matter. The rest is made up of

a mysterious substance called dark matter and a force called dark energy. Everything we see on Earth is made up of matter. For this course we will ONLY focus on this type of matter. Matter is made up of atoms. Atoms have mass and volume and so does matter. Now, look at the concept of “ATOM” as described by the atomic theory….

ATOMIC THEORY: All matter is composed of discrete units called atoms. It began as a philosophical concept in ancient Greece and entered the scientific mainstream in the early 19th century when discoveries in the field of chemistry showed that matter did indeed behave as if it were made up of atoms. An atom is made up of subatomic particles: protons (positive charge), neutrons (neutral charge) and electrons (negative charge). Each type of atom has a specific number of protons that is unique to it. Isotopes are atoms with the same number of protons but have different numbers of neutrons.

Atoms have energy stored in them in the form of chemical and nuclear energy. So, there are two possible reactions matter can undergo: Chemical and nuclear. In chemical reactions, atoms combine with each other to form new substances due to electron sharing or transfer among participating atoms. In Nuclear reactions, nuclear particles of an atom are rearranged causing the formation of a different type of atom or atoms. When a single atom is split into one or more types of atom, it is a Nuclear FISSION reaction. When two or more atoms to combine and form one or more different atoms, it is a nuclear FUSION reaction.

Most of our study of Chemistry will focus on Chemical reactions. We will only briefly investigate Nuclear reactions.

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13 3.1 Properties of Matter:

1. All matter is made up of atoms (Atomic Theory) and has mass and volume. 2. Made up of pure substances or mixtures of them. A substance is a form of matter with a uniform and

unchanging composition. 3. An element is a pure substance that cannot be broken down into simpler substances by chemical means.

An element is composed of atoms that have the same number of protons (atomic number) in its nucleus as all other atoms of that element.

4. When two or more atoms combine through a chemical reaction, a compound or molecule is formed. 5. Each pure substances has a specific chemical formula and unique physical and chemical properties that are

unique to it. [Chemical formula: a recipe of the types and number of atoms found in a compound]

a. Physical properties can be observed without changing a substance’s chemical composition. Color, hardness, and density, boiling point are examples.

b. Chemical properties cannot be observed without changing the composition of a substance. Examples: the tendency of iron to form rust when exposed to air, reactivity with acids or bases, nonreactivity with oxygen, reactivity with oxygen and etc.

6. Matter has extensive and intensive properties: a. Extensive properties: change with the amount of matter= ex: Mass, volume

b. Intensive properties: are inherent to each substance and do not depend on the amount of matter= Ex: boiling and freezing points, density, color.

Figure-2:Classification of matter concept map: Examples:

Q: Write the following examples beside the matching description of matter in Figure-2 above:

Baking soda (NaHCO3), sweet tea, sea water, blood, pure silver, salt (NaCl), sugar (C12H22O11), granite, nitrogen gas (N2), milk, pure water (H2O), mercury, carbon dioxide (CO2), air, tooth paste, dish soap, Gatorade, chicken and noodle soup, chocolate chip cookie, Coca Cola, ozone (O3)natural gas (CH4) pure gold and sulfur.

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PURE SUBSTANCES: sample of matter with both definite and constant composition and distinct chemical properties

1. Elements: is a substance whose atoms all have the same number of protons. Elements differ from each other due to proton numbers. Elements are the simplest form of substances because they cannot be broken down any further. Most elements are formed with isotopes. Isotopes are atoms with the same number of protons but have different numbers of Neutrons.

Ex: Carbon (C), hydrogen (H) and Oxygen (O) are three different elements. C-12, C-13 and C-14 are isotopes (species of atoms) of carbon. Carbon, the element is made up of all three

isotopes of carbon.

Figure-3 Isotopes of Carbon:

2. Compounds: substances with a definite composition that are made up of 2 or more atoms. These substances form molecules that are made up of specific ratios of specific atoms. Compounds are formed when elements undergo chemical reactions. Compounds can also decompose and form elements.

Figure-4: Pure substances and how they are constructed (Glucose molecula and the element, carbon)

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13 Table-1: Some common substances and their molecular formulas

Ethyl alcohol (vodka), glucose (dextrose) and citric acid (vinegar) are all chemical compounds (molecules) that are made up of the elements C, H and O. The number of atoms in the chemical formula is shown as subscripts.

MIXTURES: When pure substances mix together, mixtures are formed.

1. Homogeneous mixtures have a uniform composition – the components are indistinguishable. These are also called SOLUTIONS, even if they are not liquid mixtures. Ex. Water and sugar solution, cocoa powder and flour mixture.

2. Heterogeneous mixtures do not have a uniform composition – different phases can be seen. Ex: solid and liquid (water, sand and oil) or small and large particles (granite chips and salt crystals), different colored particles (copper sulfate, sulfur and salt crystals), etc.

Q: Label models of substances given below as pure substances or mixtures and state is they are homogeneous or heterogeneous, elements and molecules/compounds.

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13 3.2 Changes in MatterAll types of matter undergo both physical and chemical changes

3.2.1 Physical changes in matter:

States of matter: Solid, liquid, gas and plasma. We will be studying the other 3 states shown in the figure below in detail.

Q: Describe models of states of matter below by Labeling each as gas, liquid or solid:

3.2.2 Chemical changes in matter:

Matter undergoes chemical changes when atoms share or exchange electrons and rearrange to form new substances.

3.2.2.A. Signs of chemical change may include any of the following: 1. Formation of new compounds or break down of a compound 2. a new gas is formed (bubbling is observed) 3. a new solid is formed (solid/ powder or precipitate is seen at the bottom of container) 4. a new colorful substance is formed (color change) 5. A temperature change occurs:

i. Exothermic reaction = energy is released causing the system to warm up ii. Endothermic reaction = energy is absorbed causing the system to cool down

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13 3.2.2.B. All chemical reactions obey 3 fundamental laws: 1. Law of mass conservation: (Antoine Lavoisier, 1773) mass in an isolated system is neither created nor

destroyed by chemical reactions or physical transformations. Thus, the mass of the products in a chemical reaction must equal the mass of the reactants.

Mass of sample: 12.0 g + ______g à 44.0 g

2. Law of definite proportions: (Joseph Proust, 1794) a chemical compound is always composed of the same

proportions of elements by mass.

Mass of sample-1: 12.0 g + ______g à 44.0 g CO2

Mass of sample-2: 24.0 g + ______g à 88.0 g CO2

3. Law of multiple proportions: (John Dalton, 1803) If two elements form more than one compound between them, the second element will combine with fixed mass of the first element in small whole number ratios.

How to write chemical equations

1. In a chemical reaction, the reactants are written on the left-hand side and the products are written on the right-hand side of the equation.

2. An arrow (→) pointing towards the products is inserted between the reactants and the products 3. Each individual substance’s chemical formula is separated from others by a plus sign. 4. The state of matter of each compound or molecule is indicated in subscript next to the compound by an

abbreviation in parentheses. For example, a compound in the gas state would be indicated by (g), solid (s), liquid (l), and aqueous (aq). Aqueous means dissolved in water; it is a common state of matter for acids, bases, and dissolved ionic compounds.

5. The stoichiometric coefficients (the numbers in front of the chemical formulas) result from the law of conservation of mass and the law of conservation of charge (see the “Balancing Chemical Equations” section for more information).

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13 PERCENT COMPOSITION: The law of definite proportions states that regardless of the amount, a compound is always composed of the same elements in the same proportion by mass. So, the percent of each element in a given compound will be the same in any pure sample of that compound.

Q. What is the percent composition of C, H and O in C2H2O (atomic masses: C= 12g, H=1g, O = 16g) Unit 3: Practice questions -1 Q1. A 20.0-g sample of sucrose contains 8.4 g of carbon. What is the mass percentage of carbon in sucrose? Show your

work. Q2. Which of the following compounds can be used to explain the law of multiple proportions?

a. C2H2O b. CH3CH2OH c. C3H8O2 d. CO2

Q3. Ibuprofen has the chemical formula C13H18O2. It is 75.69% carbon, 8.80% hydrogen, and 15.51% oxygen. How many mg of carbon does a 200.0-mg tablet of ibuprofen contain?

Q4. Which of the following has the lowest percent composition of Carbon? a. C2H6O b. C2H3Br c. CO2 d. CO

Q4. For each compound in the table, fill in the ratio of the mass of oxygen to the mass of hydrogen. Compound Mass of Oxygen Mass of Hydrogen Mass O/Mass H

H2O 16 g 2 g _____________

H2O2 32 g 2 g _____________

a. Write a brief statement comparing the two mass ratios from the table.

b. Are H2O and H2O2 the same compound? Explain your answer.

Mass percentage of an element (%) =mass of element

mass of compound´ 100%

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3.3 Physical Separations of mixtures: When two or more substances, that do not react chemically, are blended together, the result is a mixture in which each component retains its individual identity and properties. The separation of the components of a mixture is a problem frequently encountered in chemistry. The basis of the separation is the fact that each component has a different set of physical and chemical properties.

1. Decanting: is the pouring of a liquid from a solid-liquid mixture, leaving the solid behind.

2. Filtration: used to separate a mixture of solids or solid and liquid mixture by passing it through a porous membrane to separate matter based on differences in particle size.

3. Chromatography: A mixture is dissolved in a fluid (called the mobile phase) and passed through a static material (called the stationary phase). The different components of the mixture travel at different speeds, causing them to separate. A Retardation factor can then be calculated this way: Rf value = distance component travels ÷ distance solvent travels.

Ex: Gas chromatography, paper chromatography, thin-layer chromatography, gel electrophoresis and column chromatography.

4. Evaporation: used to separate a solid that is dissolved in a liquid by heating it to its boiling point, causing vaporization, and then condensing the vapors into the liquid state and collecting the liquid. Separation of two or more liquids requires that they have different boiling temperatures.

5. Centrifugation: is the process of separating a suspended solid from a liquid by spinning the mixture in a tube at high speed inside a centrifuge. Sedimentation occurs based on density of contents in the mixture. The most dense matter will be at the very bottom of the tube and the least dense matter will be at the very top.

6. Extraction: is the removal of one substance from a mixture because of its greater solubility in a given solvent.

7. Sublimation: is the physical property of some substances to pass directly from the solid state to the gaseous state without the appearance of the liquid state. Not all substances possess this characteristic. Iodine (I2), naphthalene (C10H8, mothballs), ammonium chloride. (NH4Cl) and dry ice (solid CO2) are some substances which sublimation.

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13 Name: ________________________ ______ Period__ Seat__ Due Date:____________ Score:_______/ 100 Unit-3_Homework Problems_ Matter—Properties and Changes A new gas is formed Label each property as either physical or chemical:

__________________ 1. Chemical formula H2O __________________ 2. Forms green carbonate when exposed to moist air __________________ 3. Remains unchanged when in the presence of nitrogen __________________ 4. Colorless __________________ 5. Solid at normal temperatures and pressures __________________ 6. Ability to combine with another substance __________________ 7. Melting point __________________ 8. Liquid at normal temperatures and pressures __________________ 9. Boiling point is 100°C __________________ 10. Conducts electricity __________________ 11. Density

For each statement below, write true or false.

__________________ 12. All matter that we encounter in everyday life exists in one of three physical forms.

__________________ 13. A solid has definite shape and volume.

__________________ 14. A liquid has a definite shape and takes on the volume of its container.

__________________ 15. A gas has both the shape and the volume of its container.

__________________ 16. The particles in a gas cannot be compressed into a smaller volume.

__________________ 17. Liquids tend to contract when heated.

__________________ 18. The particles in a solid are spaced far apart.

__________________ 19. The words gas and vapor can be used interchangeably.

20. Sort the contents into box as physical or chemical change: boil crumple crush explode

burn ferment freeze grind

condense melt oxidize rot

corrode rust tarnish vaporize

Physical Change Chemical Change

1. __________________________ 9. _____________________

2. __________________________ 10. _____________________

3. __________________________ 11. _____________________

4. __________________________ 12. _____________________

5. __________________________ 13. _____________________

6. __________________________ 14. _____________________

7. __________________________ 15. _____________________

8. __________________________ 16. _____________________

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13 For each item in Column A, write the letter of the matching item in Column B:

Column A Column B

_____ 21. The new substances that are formed in a chemical reaction

_____ 22. A chemical reaction that involves one or more substances changing into new substances

_____ 23. Shows the relationship between the reactants and products in a chemical reaction

_____ 24. States that mass is neither created nor destroyed in any process

_____ 25. The starting substances in a chemical reaction

a. chemical change

b. reactants

c. products

d. chemical equation

e. law of conservation of mass

Answer the following question. Write an equation showing conservation of mass of reactants and products.

26 In a laboratory, 178.8 g of water is separated into hydrogen gas and oxygen gas. The hydrogen gas has a mass of 20.0 g.

I. Write a chemical equation for this reaction:

II. What is the mass of the oxygen gas produced?

For each item in Column A, write the letter of the matching item in Column B.

Column A Column B

______ 27. Separates substances on the basis of the boiling points of the substances

______ 28. Separates by formation of solid, pure particles from a solution

______ 29. Separates substances based on their movement through a special paper

_____ 30. Separates solids from liquids by using a

a filtration

b. distillation

c. crystallization

d. chromatography

porous barrier