8/6/2019 chem qtr1

1/6

Alyssa Jane E. Boller

Chemistry 1Quarter 1

TOOLS IN CHEMISTRY

Scopes: Quantitative - associated with numbers (volume, mass, concentrations Qualitative - associated with kind or quality (color, sweetness)

Rules on the Use of Significant Figures: All non-zero digits are significant

467.89 = 5 sf Zeros between non-zero digits are significant

8.0098 = 5 sf Trailing zeros are siginificant only if the decimal point is specified

3.00 = 3 sf 300 = 1 sf Zeros before a decimal point are not significant

0.54 = 2 sf When there are no digits before a decimal point or when the digit before the

decimal point is zero, the zeros after the decimal point preceding other digitsare not significant

0.078 = 2 sf *Scientific notations remove the doubt in determining the number of

significant figures.1.23x10 8 = 3 sf

*the coefficient determines the number of sigfig*Significant figures do not apply to exact numbers. Exact numbers such as the

number 60 in the statement "there are 60 minutes in an hour" is said to havean unlimited number of significant figures.

Addition and Subtraction:- the final answer should never have more decimal places than themeasurement with the least number of decimal places

Multiplication and Division:- the final answer should follow the number of significant figures ofthemeasurement/factor with the least number of significant figures

Rules for Rounding Off Numbers: If the digit to be removed is less than 5, drop the digit and leave the remaining

number unchanged If the digit to be removed is equal to or greater than 5, drop the digit and

increase the preceding digit by one.

Dimensional Analysis:Conversion Factor - A fraction whose numerator and denominator are of the

same quantity expressed in different units

DESIRED unitGIVEN unit x ------------------- = DESIRED unit

GIVEN unit

MATTER

8/6/2019 chem qtr1

2/6

- anything that occupies space and has mass

States/Phases: Solid

- Has definite shape and definite volume- Rigid

- Molecules are held tightly together- Molecules can vibrate only very slightly Liquid

- Distinct volume independent of its container- No specific shape- Molecules slide over each other- Pours easily

Gas- No fixed volume or shape- Molecules are very far apart and are moving at high speeds- Molecules colliding repeatedly with each other and with the walls of the

container

Properties: Physical- Can be determined without changing the nature of the substance

Chemical- Described the ability of a substance to participate in chemical reactions

Intensive- Do not depend on the amountof the sample being examined

Extensive- Depends on the quantity of the sample

Changes: Physical

- Changes that alter the physical form of matter without changing its chemicalidentity

- Changes in state Chemical

- Occurs when the chemical identity of a substance is destroyed and a newsubstance is formed

- Chemical reactions

Processes: Endothermic

- the system absorbs heat- heat flow into the system

Exothermic- the system evolves heat- heat flows out of the system

Classification: Substance

- has its own set chemical and physical properties- cannot be separated into parts by physical means- has a definite, fixed composition that does not vary from one sample to

another

8/6/2019 chem qtr1

3/6

Mixture- consists of two or more chemicals- properties depend on the substances on it- composition can vary

Heterogenous - varies in composition

Homogenous - has the same/uniform composition throughout

Classification of Substances: Element

- defined by its atomic number- cannot be created or decomposed into simpler substances by ordinary

chemical process. Compound

- a substance made of more than one type of atom- composed of 2 or more elements- atoms combined in fixed proportions- can be decomposed into two or more other substances by chemical change

Types of Compounds: Acids

- turn blue litmus to red- react with many metals- react with bases- react with carbonates (HO 3) and bicarbonates (H 2CO 3) to produce carbon

dioxide gas- Aqueous acid solutions conduct electricity- pH (power of hydrogen) < 7

Oxoacid- acid that contains hydrogen, oxygen, and another element

Base- yields hydroxide ions (OH -) when dissolved in water- bitter taste- slippery- cause color changes in plant dyes- Aqueous base solutions conduct electricity- pH > 7- turn red litmus to blue

Salt- formed when one or more of the hydrogen ions of an acid react with one or

more hydroxide ions of a base

Types of Mixtures: Suspension

- >1000 nm- particles are more or less evenly dispersed throughout a liquid or gas- different parts separate over time- temporary heterogenous mixtures

Solution- 0.2-2.0 nm- A homogenous mixture of two or more substances uniformly dispersed

throughout a single phase

8/6/2019 chem qtr1

4/6

Colloid- 2.0 - 1000 nm- consists of tiny particles that are suspended in a liquid, solid or gas- particles do not settle- exhibits Tyndall Effect

Coarse Mixture- mixture of substances when you mix all the substances, you can see that thesubstances are mixed but not dissolved

Separating Mixtures: Decantation

- separates liquids from solids that have sttled Evaporation

- separates the solid (residue) from the liquid (filtrate) parts of the mixture Distillation

- separate components of a mixture of liquids based on their boling points Filtration

- separates solids from liquid parts of the mixture Centrifugation

- separate substances of different densities Chromatography

- separates components of mixtures based on how quickly moleculesdissolved in a mobile phase solvent move along a solid phase

Subatomic Particles: Protons - positive-charged particles Neutrons - neutral Electrons - negative-charged particles

Atomic Number (Z)- number of protons in the nucleus

Mass Number (A)- number of protons + the number of neutrons

Atomic Mass- The average mass of all atoms of an element as they occur in nature

Atomic Mass Unit- Exactly 1/12 the mass of a carbon-12 atom- 1 amu = 1.66x10 -24 g

Isotopes- atoms of the same element (X) with different numbers of neutrons in their

nuclei

Isotopic Mass- the mass of a given isotope

8/6/2019 chem qtr1

5/6

Isobars- atoms or ions having the same atomic mass but different atomic numbers.

They are generally formed by subsequent beta emissions in which theatomic number changes by one unit but the atomic mass of beta particles arenegligible as compared to neutrons or protons

- the atoms or ions having same atomic mass but different atomic numbers

- different number of protons; same mass numberIsomers

- compounds with the same molecular formula but different structuralformula. Isomers do not necessarily share similar properties until they also havethe same functional groups

Allotropes- different forms of the same element in the same physical state- Diamond and Graphite

Ion- an atom, or group of atoms, that has a net positive or negative charge

cation- ion with a positive charge- loses one or more electrons

anion- ion with a negative charge- gains one or more electron

Molecule- an aggregate of two or more atoms in a definite arrangement held together

by chemical bonds Diatomic Molecule

- contains only two atoms- H 2 N2 F2 O 2 I2 Cl2 Br 2 (Have No Fear Of Ice CoLd BeeR

Polyatomic Molecule- contains more than two atoms

Molecular Formula- shows the exact number of atoms of each element in the smallest unit of a

substance

Empirical Formula- shows the simplest whole-number ration of the atoms in a substance

John Dalton- Father of Modern Atomic Theory

- Research in color blindness Atomic Theory:

Elements- composed of small particles called atoms- all atoms of a given element are identical- the atoms of one element are different from the atoms of all

others Compounds

- composed of atoms of more than one element combined

8/6/2019 chem qtr1

6/6

- the relative number of atoms of ach element is always the same

Chemical Reactions- rearrangement of atoms- atoms are not created nor destroyed

Law of Definite Composition- Proust's law- Made by John Proust (French Chemist)- A chemical compound always contains the same proportion of elements by

massLaw of Multiple Proportions

- Dalton's law- If 2 elements form more than 1 compound between them, then the ratios of

the masses of the second element which cobined with a fixed mass of the firstelement will be rations of small whole numbersLaw of Conservation of Mass

- Lomonosov-Lavosier Law

- The mass of substances in a closed system will remain constant, no matterwhat processes are acting inside the system- the mass of the reactants must always be equal to the mass of the products

Limiting Reactant- Limits the production of products- Totally consumed in a reaction- Determines the amount of products

Accuracy- closeness to true value

Precision- reproductability of values

1 drop -> about 0.05ml20 drops -> about 1 mlFew drops -> 1-2 dropsSeveral drops -> 3-5 drops

Graduated beakers & Erlenmeyer flasks- accurate to about +- 10 ml

Graduated cylinder- accurate to about +- 0.5 ml

Burettes, Volumetric Flask & Transfer Pipettes- accurate to about +- 0.01 ml

Mass - measure of the quantity of matterWeight - pull of gravity on an object