# Basics of Chemistry

## What are some basics?

• Units of Measurement
• Scientific Notation and Dimensional Analysis
• How reliable are Measurements?
• Representing data in different ways
• Properties of matter
• Change in matter
• Mixtures of Matter
• Elements and Compounds

## SI Units

SI measurement units allow scientists to reuse or test measurements reported by other scientists. SI base units could be meter for length or second for time. By adding prefixes to SI units, it extends the range of possible measurements.

## Scientific Notation and Dimensional Analysis

Scientific Notation makes it easy to handle huge or small measurements. Numbers that have been added or subtracted in scientific notation must be shown to the same power of ten. When measurements are multiplied or divided in scientific notation, their exponents are added or subtracted in the right way.

Dimensional Analysis usually uses conversion factors to solve problems that involve units. A conversion factor is a ratio of an equivalent values.

TEK- 2(G)

## How reliable are measurements?

An accurate measurement is close to the accepted value. Precise measurements show little variation over a series of trials. The type of measurement instrument determines the degree of precision possible. The percent error compares the size of an error in experimental data to the size of the accepted value.

The number if significant figures reflects the precision of the reported data. Answers to calculations are normally always rounded off to maintain the correct number of significant figures.

TEKS- 2(F)

## Representing data in different ways

• Graphs are visual representations of data. They can reveal patterns in the data.
• Circle graphs show the parts of a whole.
• Bar graphs show how a factor varies with the time, location, and temperature.
• The relationship between the independent variables and the dependent variables on a line graph can be linear or nonlinear.

TEK- 2(I)

## Properties of Matter

Substance- a form of matter with a uniform and unchanging composition.

Physical properties- the uniform composition of an object.

Chemical properties- properties that become evident during a change or reaction.

Chemical and physical properties are affected by outside conditions like temperature. A chemical change would be rust on a old tractor. A physical change would be like dropping an egg and watching it bust. There are three common states of matter: solid- like an apple, liquid- like a dr. pepper, and gas- like fog. You can compare the three states in terms of compressibility, volume, structure, shape, and volume.

TEK- 4(A)

## Changes in Matter

Physical change- alters the physical properties of a substance without changing its composition.

Chemical change- changes the substances composition,

The Law of Conservation of Mass says that mass is neither created nor destroyed while a chemical reaction occurs; its conserved. In a chemical reaction reactants form products.

Intensive property- does not depend on system size or the amount of material in the system.

Extensive property- Is directly proportional with the material in the system.

http://cy.tl/NUWzSJ

TEK- 4(A,B)

## Mixtures of Matter

Mixture- a physical blend of to or more pure substances in any proportion.

Homogeneous Mixture- has a constant composition or a single phase.

Heterogeneous Mixture- does not blend smoothly throughout.

Mixtures can be separated by physical means. Usually they are separated by filtration, distillation, crystallization, and chromatography. Solutions are homogeneous mixtures.

## Elements and Compounds

Elements- substances that cannot be broken down into simpler substances through chemical or physical means.

Compound-chemical combination of two or more elements.

Matter is divided into two things, mixtures and pure substances. The mixtures can be divided into two things also, Heterogeneous mixtures an homogeneous mixtures. Pure substances can be divided into elements and compounds. This is an easy way to classify matter.

http://youtu.be/d0zION8xjbM

2 (G,H,I)

4 (A,B,C,D)

5 (A,B)

8 (D,E)