Math Review for Chemistry



Unit 1: Introduction to Chemistry



Key Ideas

• Matter is classified as a pure substance or as a mixture of substances. (3.1q)


• The three phases of matter (solids, liquids, and gases) have different properties. (3.1kk)

• A pure substance (element or compound) has a constant composition and constant properties throughout a given sample, and from sample to sample. (3.1r)

• Elements cannot be broken down by chemical change. (3.1u)

• Mixtures are composed of two or more different substances that can be separated by physical means. When different substances are mixed together, a homogeneous or heterogeneous mixture is formed. (3.1s)

• The proportions of components in a mixture can be varied. Each component in a mixture retains its original properties. (3.1t)

• Differences in properties such as density, particle size, molecular polarity, boiling point and freezing point, and solubility permit physical separation of the components of the mixture. (3.1nn)

• A solution is a homogeneous mixture of a solute dissolved in a solvent. The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical natures of the solute and solvent. (3.1oo)

• Energy can exist in different forms, such as chemical, electrical, electromagnetic, thermal, mechanical, and nuclear. (4.1a)

• Heat is a transfer of energy (usually thermal energy) from a body of higher temperature to a body of lower temperature. Thermal energy is the energy associated with the random motion of atoms and molecules. (4.2a)

• Temperature is a measurement of the average kinetic energy of the particles in a sample of material. Temperature is not a form of energy. (4.2b)

• The concepts of kinetic and potential energy can be used to explain physical processes that include: fusion (melting), solidification (freezing), vaporization (boiling, evaporation), condensation, sublimation, and deposition. (4.2c)

• A physical change results in the rearrangement of existing particles in a substance. A chemical change results in the formation of different substances with changed properties. (3.2a)

• Chemical and physical changes can be exothermic or endothermic. (4.1b)

• The structure and arrangement of particles and their interactions determine the physical state of a substance at a given temperature and pressure. (3.1jj)

Matter Activity

|Station Number/ |Description/Observations |Classification |How do you know? |

|Identity of Substance | |(Element, | |

| | |Compound, | |

| | |Homogeneous Mixture, | |

| | |Heterogeneous Mixture) | |

|1 | | | |

|2 | | | |

|3 | | | |

|4 | | | |

|5 | | | |

|6 | | | |

|7 | | | |

|8 | | | |

|9 | | | |

|10 | | | |

|11 | | | |

|12 | | | |

|13 | | | |

|14 | | | |

Questions:

1. How could you tell a substance is an element?

2. What phases can elements be in?

3. How could you tell a substance is a compound?

4. What phases can compounds be in?

5. How could you tell a sample is a mixture?

6. What phases can mixtures be in?

7. How do you know the difference between a homogeneous and heterogeneous mixture?

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Matter Practice

Classify each of the following with the combination of terms listed below.

pure substance – element mixture – homogeneous

pure substance – compound mixture – heterogeneous

1. HCl (aq) 2. sugar (C11H22O11) 3. KBr (s) 4. Soil

5. Cl2 (g) 6. water 7. CH2(OH)2 (aq) 8. Sodium

9. Hg (l) 10. iron oxide 11.NH3 (l) 12. salt water

13. Matter that is composed of two or more different elements chemically combined in a fixed proportion is classified as

(1) a compound (2) an element (3) a mixture (4) a solution

14. A compound differs from an element in that a compound

(1) is homogeneous

(2) has a definite composition

(3) has a definite melting point

(4) can be decomposed by a chemical reaction

15. A compound differs from a mixture in that a compound always has a

(1) homogeneous composition

(2) maximum of two elements

(3) minimum of three elements

(4) heterogeneous composition

16. A heterogeneous material may be

(1) an element

(2) a compound

(3) a pure substance

(4) a mixture

17. Which statement is an identifying characteristic of a mixture?

(1) a mixture can consist of a single element

(2) a mixture can be separated by physical means

(3) a mixture must have a definite composition by weight

(4) a mixture must be homogeneous

18. Which must be a mixture of substances?

(1) solid (2) liquid

(3) gas (4) solution

19. Which substance can be decomposed by chemical means?

(1) aluminum (2) octane (3) silicon (4) xenon

20. Which substance can be decomposed by chemical means?

(1) ammonia (2) oxygen

(3) phosphorus (4) silicon

21. Which substance can not be broken down by a chemical reaction?

(1) ammonia (2) argon (3) methane (4) water

22. Two substances, A and Z, are to be identified. Substance A can not be broken down by a chemical change. Substance Z can be broken down by a chemical change. What can be concluded about these substances?

(1) Both substances are elements.

(2) Both substances are compounds.

(3) Substance A is an element and substance Z is a compound.

(4) Substance A is a compound and substance Z is an element.

23. Which terms are used to identify pure substances?

(1) an element and a mixture

(2) an element and a compound

(3) a solution and a mixture

(4) a solution and a compound

24. Two different samples decompose when heated. Only one of the samples is soluble in water. Based on this information, these two samples are

(1) both the same element

(2) two different elements

(3) both the same compound

(4) two different compounds

25. Tetrachloromethane, CCl4, is classified as a

(1) compound because the atoms of the elements are combined in a fixed proportion

(2) compound because the atoms of the elements are combined in a proportion that varies

(3) mixture because the atoms of the elements are combined in a fixed proportion

(4) mixture because the atoms of the elements are combined in a proportion that varies

Drawing Particle Arrangements

Draw a diagram of a:

pure diatomic pure diatomic mixture of mixture of mixture of

element compound two elements an element & two diatomic

a compound elements &

a compound

1.) In terms of composition/type of atoms, what is the difference between a monatomic element, a diatomic element, and a diatomic compound?

2.) Use the following key for parts a-c. = element X = element Z

a.) 8 atoms of element X in gaseous form b.) 4 molecules of compound X2Z in liquid form

c.) Homogeneous mixture of element Z with element X (10 atoms of each element).

Phases and Phase Changes

Directions: Using the boxes provided below as your container, place six circular molecules in each container representing the given phase. Then on each line with the arrow label which phase change is occuring. Last fill in the chart below about phases using the words provided in the parenthesis.

SOLID (s) LIQUID (l) GAS (g)

| |Solid |Liquid |Gas |

|Shape | | | |

|(Has a fixed shape or takes the shape of| | | |

|the container) | | | |

|Volume | | | |

|(Has a fixed volume or takes the volume | | | |

|of the container) | | | |

|Density | | | |

|(high or low) | | | |

| | | | |

|Particle arrangement | | | |

|(rigid or free) | | | |

| | | | |

|Attraction | | | |

|(particles are highly attracted and | | | |

|close or weakly attracted and spread | | | |

|out) | | | |

Unit 1 Review

Regents Chemistry

METRIC

1. Using tables on page one of your reference table you should be able to identify which unit is used to measure each quantity and you should be able to convert between units using the prefixes. Locate the prefix assigned to the measurement unit that you are starting with and then find the prefix that you want to convert to. Count the number difference between the factors and then move your decimal that many places.

a. Identify the unit used for each quantity:

(1) mass _________ (4) temperature __________

(2) volume _________ (5) length __________

(3) energy _________ (6) time __________

b. Convert the following:

(1) 568 mL to L ___________________

(2) 0.00897 g to mg ___________________

(3) 45700 mm to km ___________________

2. Density is the measurement of mass divided by volume. A substance’s density can help identify it. For example, water’s density is 1.00g/mL. Substances float in water of they have low densities, and sink when their densities are greater than 1.00 g/mL.

a. Calculate the density of 5.00 gram sample of an unknown substance, which has a volume of

5.15mL.

b. Using table S, identify the unknown substance in question (a) above. __________________________

c. Calculate the mass of a substance with a density of 2.50 g/mL and a volume of 23.0mL.

d. Calculate the volume of a metal rectangle with a height of 2.0cm, a length of 3.0cm, and a width

of 1.0cm.

e. If the metal in question (d) above is iron, calculate the mass. (Hint: density is on table S)

SCIENTIFIC NOTATION

3. Scientific Notation is used to represent very small or very large numbers. Convert the following to scientific notation:

a. 0.00000345 ____________________________

b. 1098000000 ____________________________

c. 0.000345 ____________________________

d. 0.000005677 ____________________________

SIGNIFICANT FIGURES

4. All whole numbers 1-9 count. Preceding zeros never count, trapped zeros always count, and trailing zeros count IF THERES A DECIMAL before the zero. Count the number of significant figures:

5678 0.09809 0.00345 0.0712

0.0987 10000 10200 102.0986

5. When rounding, your answer can only be as precise as your least precise measurement. When adding or subtracting numbers, round your answer to the lowest decimal place given. When multiplying or dividing, round your answer to the least number of significant figures. Calculate and round to the correct number of significant figures:

a. 4.567 + 1.2 = _____________ d. 67065/87.2 = ________________

b. 678.345-234.98 = ______________ e. (54.0-32.34)/1.202 = ________________

c. 45 x789 = _____________ f. 3.108*(98.70-8.20) = __________________

ELEMENTS, COMPOUNDS, AND MIXTURES

6. Matter is anything that has a mass and takes up space. An element is the simplest form of matter, which cannot be broken down any further. Elements are listed on Table S and the periodic table. Their symbols start with an uppercase letter.

a. Which of the following is not matter? _____________________

Magnesium Calcium Carbonate Salt water Heat

b. Which of the above is an element? _____________________

7. Compounds are composed of two or more elements. They can only be decomposed chemically. Elements and compounds are also known as substances.

a. Which of the choices in number one was a compound? ________________________

b. How can compound be broken down? __________________________________________________

c. Which of the choices in question one are substances? ______________________________________

8. Mixtures are physical combinations of two or more substances (elements and/or compounds). Mixtures can be homogeneous (completely mixed, cannot see the parts) or heterogeneous (unevenly mixed, can see the parts). Mixtures can be separated by physical means. Label each as homogeneous or heterogeneous:

Sand: ____________________ Brass: ______________________________

Milk: ____________________ Oil and water: ________________________

9. Compounds must be separated chemically but mixtures can be separated easily using physical methods.

a. Match each method with its name.

Distillation Separated by differences in particle size

Filtration To pour off the top layer of an uneven mixture

Decant Separated by differences in boiling point.

Chromatography Just a test for purity

b. Which of the above processes only work if the mixture is heterogeneous? _____________________

10. Mixtures are composed of solutes that dissolve and solvents that do the dissolving. The solute should be the smaller quantity.

a. In iced tea, what is the solute? ___________________ solvent? ________________________

b. In air, name a solute: _________________

c. Do all solvents have to be water? Explain. _______________________________________________

SOLIDS, LIQUIDS, AND GASES

11. A solid has a definite shape and volume. Solids are arranged in a geometric pattern. Liquids have a definite volume but take the shape of the container they are in. Gases have an indefinite shape and volume; they take the shape and volume of the container. Gases are easily compressed.

a. Draw particle diagrams for a solid, liquid, and a gas using at least 5 particles:

b. Which has a definite shape?

HCl(g) H2O(l) Cu(s)

c. Which has a definite volume?

LiF(g) Br2(l) Mg(s)

12. Vapors are the gas phase of substances that are normally solid or liquid at room temperature. Which can be a vapor?

Carbon dioxide ______ Water _____ Oxygen _____

13. Phase changes occur when heat is given to or taken from a sample. For each of the following, give the phases involved and if it is endothermic or exothermic.

Evaporation ___________________________ __________________________

Melting ___________________________ __________________________

Deposition ___________________________ __________________________

Boiling ___________________________ __________________________

Condensation ___________________________ __________________________

Sublimation ___________________________ __________________________

CHANGES IN THE LAB

14. Physical changes are changes where the substance retains its properties. Chemical changes will make substances change into new substances and change properties.

a. Label the following as physical (P) or chemical (C) properties:

Texture ____ flammability ____ boiling point: ____

Odor ____ color ____ chemical composition: ____

b. Label the following as physical (P) or chemical (C) changes:

Corrosion: ____ melting: ____ mixing: ____

Freezing: ____ cutting: ____ decaying: ____

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Matter

Anything that has mass and volume (takes up space)

CAN be separated by PHYSICAL means

Can NOT be separated by physical means

MIXTURES (each piece is different – not pure)

PURE SUBSTANCES (each piece looks the same – PURE!)

-each piece has exact same composition.

Can NOT be separated by chemical means

Separated by chemical means, only

Different composition throughout

Same composition throughout

HETEROGENEOUS MIXTURE (not uniform throughout— a pattern)

Example: Italian dressing, concrete, soil, chocolate chip cookie

Hetero = opposite

HOMOGENEOUS MIXTURE (uniform throughout—distinct pattern)

Example: saltwater, iced tea

Homo = same

ELEMENT (simplest form of matter)

Example: Na, Cl2

COMPOUND or MOLECULE

(2+ different elements chemically combined)

Example: NaCl (table salt), H2O (water)

Particle Diagram

Particle Diagram

Particle Diagram

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