Chemistry Midterm

Qualitative observations

Based on your senses and observations

quantitative observation

Involves numbers and measurements

All parts of a lab write-up (in order)

Title, purpose, procedure, data and observations, calculations, conclusion and questions

Intensive properties

do not depend on the amount of matter present

Extensive properties

depend on the amount of matter that is present

Physical vs. chemical change

Physical - does not create a new substance, atoms are not rearranged into different compounds; Chemical - converts one substance into another; atoms are rearranged

compounds

2 or more different elements chemically combined; composition always remains the same

elements

A molecule composed of one kind of atom; cannot be broken into simpler units by chemical reactions.

homogeneous material

an item that consists of only one material throughout or a combination of multiple materials that cannot be mechanically disjointed, excluding surface coatings

heterogeneous material

a material with a composition that varies from one point to the next within its structure

mixtures

A combination of two or more substances that are not chemically combined and have varying composition (wood, soda, coffee, air)

molecules

Groups of two or more atoms held together by chemical bonds

Difference in melting points for pure substances vs mixtures

Pure substances have definite melting points; mixtures do not

Methods of separating mixtures

filtration, distillation, crystallization, chromatography, magnet, sorting by color, centrifuging

Characteristic of solids and the atoms/molecules within them

Have definite shape and volume, atoms are tightly packed and vibrate in place, strong force of attraction between particles

Characteristic of liquids and the atoms/molecules within them

definite volume but no definite shape, flow, looser attractive forces

Characteristic of gases and the atoms/molecules within them

no definite volume or shape, weak attractive forces, flow

Physical property

Characteristic that can change without turning it into a different substance (odor, volume, state, density, melting point, boiling point)

Chemical property

Characteristic that describes the ability of a substance to change to a different substance

Physical change

change that does not affect a substance's composition

chemical change

substance becomes another substance (wood burning, rusting of steel, digestion of food, growth of plants)

Alloy

mixture of a metal

pure substances

always have the same composition (elements or compounds)

Matter

Must have mass and volume

Mass vs. weight

Mass is a measurement of the amount of matter something contains (makeup stays the same everywhere), while weight is the measurement of the pull of gravity on an object (changes on different planets).

Colloids

heterogeneous, shows Tyndall effect, will not settle out over time, think snickers bar or tapioca pudding

Suspensions

heterogeneous, shows Tyndall effect, settles out over time

Solutions

Homogeneous, no definite formula, type of mixture

Scientific method

1. Observations 2. Formulate hypothesis 3. Experiment -- Theory, prediction, experiment repeat enough and could end up with a law

Relationship between temperature and pressure

As temperature increases, so does pressure, and as it decreases, so does pressure (because temperature increases particle movement, they move more often and therefore hit the sides of things more, increasing pressure)

Percent composition by mass

part/whole x 100

Empirical formula

Expressing the smallest whole number ratio of atoms in a compound

Molecular formula

The actual formula of a compound

What is this and what is it for?

This is a test tube, and its purpose is to hold, mix, or heat small quantities of substances

What is this and what is it for?

This is an iron ring, and its purpose is to hold up whatever is placed on the Bunsen burner

What is this and what is it for?

This is a ring stand and it holds an iron ring. Commonly, a Bunsen burner is placed beneath it to heat whatever rests on it

What is this and what is it for?

This is a test tube rack and its purpose is to hold test tubes

What is this and what is it for?

This is a Bunsen burner and its purpose is to heat things

What are these and what are they for?

These are crucible tongs and they hold the crucible

What are these and what are they for?

These are beaker tongs and they hold the beaker

What is this and what is it for?

This is a dropper pipette and its purpose is to transfer small amounts of liquid

What is this and what is it for?

This is a watch glass and is typically used for evaporation and weighing solids

What is this and what is it for?

This is a glass stirring rod and it is for stirring solutions/mixtures

What is this and what is it for?

This is a thermometer and it is for checking the temperature of something

What is this and what is it for?

This is a scoopula and it is for scooping small amounts of things and removing/scraping substances

What is this and what is it for?

This is a test tube holder and its purpose is to carry/hold test tubes

What is this and what is it for?

This is a pipestem triangle and its purpose is to hold up the crucible while it is being heated above the Bunsen burner

What is this and what is it for?

This is a crucible and cover, and its purpose is to hold, typically solids, to give them somewhere to be while they are being burned/heated over a Bunsen burner

What are these are what are they for?

These are forceps and they help hold/carry small things

What are these and what are they for?

This is a mortar and pestle and they are for grinding/crushing solids

What is this and what is it for?

This is a graduated cylinder and its purpose is to measure amounts of liquid in milliliters

What is this and what is it for?

This is an evaporating dish and it is used to allow things to heat/evaporate over time

What is this and what is it for?

This is a wire gauze and it is for protecting glassware on a Bunsen burner by diffusing the heat

What is this and what is it for?

This is a beaker and it is for measuring liquids, containing liquids/solids, and for holding things that may be used in a reaction