Basic Chemistry: Elements, Mixtures, and Measurement Concepts

element

A pure substance made of only one kind of atom that cannot be broken down by chemical means.

compound

A substance made from two or more elements chemically bonded in fixed ratios.

homogenous mixture

A mixture with a uniform composition throughout (also called a solution).

heterogenous mixture

A mixture where the components are not uniformly distributed and can be visibly distinguished.

matter

Anything that has mass and occupies space.

mass

The amount of matter in an object, typically measured in grams or kilograms.

volume

The amount of space an object or substance occupies.

exact number

A number known with complete certainty, often from counting or defined values (e.g., 1 dozen = 12)

Measurement

A value that includes a number and a unit, obtained by using instruments (e.g., 5.0 cm).

Accuracy

How close a measured value is to the true or accepted value.

Precison

How close repeated measurements are to each other, regardless of accuracy.

How can you tell the difference between an element, a compound, a homogeneous mixture, and a heterogeneous mixture?

Element - Only one type of atom (like oxygen or gold).Compound - Two or more elements chemically joined (like water - H₂O).

Homogeneous Mixture - Looks the same throughout (like saltwater).

Heterogeneous Mixture - You can see the different parts (like salad or sand in water).

What are the common base units for the metric system and what does each measure?

Meter (m) - measures lengthGram (g) - measures mass

Liter (L) - measures volume

Second (s) - measures time

Kelvin (K) - measures temperature

How do you convert between different prefixes within the metric system?

You move the decimal left or right based on the size of the prefix. Example:

1,000 millimeters (mm) = 1 meter (m) → move decimal 3 places left1 kilogram (kg) = 1,000 grams (g) → move decimal 3 places right

How do you convert numbers into scientific notation? How do you convert numbers in scientific notation back to standard format?

To scientific notation: Move the decimal so there's 1 digit in front. Example: 45,000 → 4.5 × 10⁴

To standard form: Move the decimal based on the exponent. Example: 3.2 × 10³ → 3,200

How do you do calculations with scientific notation?

Multiply: Multiply the numbers, add the exponents Example: (2 × 10³) × (3 × 10²) = 6 × 10⁵Divide: Divide the numbers, subtract the exponents Example: (6 × 10⁵) ÷ (2 × 10²) = 3 × 10³

What are significant figures (sig figs)? Why are they important?

Significant figures are the digits that show how exact a number is.They are important because they show the precision of your measurement or calculation.

How can you determine the accuracy of your data?