CHEM 1111: Chapter 1

What is matter?

Anything that has mass and takes up space.

How are particles in a solid arranged?

They are very close together, fixed in place, and have strong interactions. Solids have a definite shape and volume.

How is a liquid different from a solid?

Liquid particles can move past each other, so liquids have a definite volume but take the shape of their container.

How is a gas different from a liquid and solid?

Gas particles are far apart and constantly moving. Gases have no definite shape or volume and are compressible.

What are the two major categories of matter?

Pure substances and mixtures.

What is a pure substance?

Matter with a fixed or constant composition that can be classified as an element or compound.

What is an element?

A pure substance that cannot be broken down into simpler substances by chemical means.

What is a compound?

A pure substance made of two or more elements chemically bonded together in a constant composition.

What is a mixture?

A combination of two or more pure substances with a variable composition.

What is the difference between a homogeneous and heterogeneous mixture?

A homogeneous mixture is uniform throughout while a heterogeneous mixture is not uniform and has different parts or phases.

What is a physical property?

A characteristic that can be observed or measured without changing the identity of the substance. Examples include density color melting point and boiling point.

What is a chemical property?

A characteristic describing how a substance can change into another substance. Examples include flammability reactivity acidity and rusting.

What is an intensive property?

A property that does not depend on the amount of substance. Examples include density color melting point and boiling point.

What is an extensive property?

A property that depends on the amount of substance. Examples include mass volume length and heat.

What is a physical change?

A change that does not change the identity or composition of the substance. Examples include melting boiling and dissolving.

What is a chemical change?

A change that forms one or more new substances and involves breaking or making chemical bonds.

How can you tell a chemical change occurred?

A new substance forms with a new composition and new physical and chemical properties.

What are the basic steps of the scientific method?

Observation hypothesis experiment and analyze results or make a conclusion.

What is a hypothesis?

A tentative explanation for observations that can be tested.

What happens if experimental results do not support a hypothesis?

The hypothesis is revised and tested again.

What is accuracy?

How close a measurement is to the actual or true value.

What is precision?

How close measurements are to each other or how reproducible they are.

What is systematic error?

Error that consistently makes measurements too high or too low.

What is random error?

Error that causes measurements to vary above and below the actual value.

What is the relationship between precision accuracy and error?

High precision means low random error and high accuracy means low systematic error.

What is an exact number?

A number known with no uncertainty usually from counting or a defined relationship.

What is a measured number?

A number obtained using a measuring device so it contains some uncertainty or error.

What digits are always significant?

All nonzero digits.

Which zeros are significant?

Captive zeros are significant and trailing zeros after a decimal are significant. Leading zeros are not significant.

What is scientific notation used for?

Writing very large or very small numbers conveniently.

What does the exponent in scientific notation tell you?

It tells you how many places and in which direction the decimal moves. Large numbers have positive exponents and numbers less than 1 have negative exponents.

What is the sig fig rule for multiplication and division?

The answer has the same number of significant figures as the measurement with the fewest significant figures.

What is the decimal place rule for addition and subtraction?

The answer has the same number of decimal places as the number with the fewest decimal places.

What rounding rule should I remember for different types of calculations?

Multiplication and division use significant figures while addition and subtraction use decimal places.

What is dimensional analysis or the factor label method?

A method of converting units by multiplying by conversion factors so unwanted units cancel.

What should you do when converting a unit raised to a power such as cm squared?

Raise both the number and the unit in the conversion factor to that power.

What is density?

A physical property relating mass to volume.

What is the density equation?

Density equals mass divided by volume.

What are common units for density?

g/mL or g/cm3 for solids and liquids and g/L for gases.

Does density depend on how much of a substance you have?

No. Density does not depend on sample size.

What happens to density when temperature increases?

Generally density decreases as temperature increases.

How can you find the volume of an irregular solid?

Use water displacement. The increase in water volume equals the object's volume when fully submerged.

What does percent mean?

Parts per hundred.

What is the basic percent equation?

Percent equals part divided by whole times 100 percent.

When using a percentage as a conversion factor what must happen to the units?

The part and whole must have the same units.

How do you convert Celsius to Fahrenheit?

Fahrenheit equals 1.8 times Celsius plus 32.

How do you convert Fahrenheit to Celsius?

Celsius equals Fahrenheit minus 32 divided by 1.8.

How do you convert Celsius to Kelvin?

Kelvin equals Celsius plus 273.15.

How do you convert Kelvin to Celsius?

Celsius equals Kelvin minus 273.15.