Chemistry Test -- Matter, Density Percent Error, Atoms, Temperature Conversions

matter, density, atoms

what is chemistry?

study of matter, its composition, its structure, its properties, and its reactions

what is matter? is air matter?

• anything that has mass and takes up space

• yes because it takes up space and has mass

what is a pure substance?

• matter that always has the same composition

• uniform composition and fixed properties

• elements and compounds

what are elements?

• cannot be broken down

• substances made up of one type of atom

• contains one type of atom

• 1st letter capital and 2nd letter lowercase

what are compounds?

• substances made of 2 or more elements that are chemically bonded

• can be broken down into simpler substances and will not have those characteristics

• properties of a compound are different than the properties of the elements that make up

what are mixtures?

• combinations of substances that are not chemically bonded together

• retain some properties of individual substances

• composition is not fixed

what are the two types of mixtures?

homogenous and heterogenous

what is an example of a homogenous mixture? explain.

• solution

• particle are too small to settle out, to be trapped by filter, to scatter light

what are 2 examples of a heterogenous mixture? explain.

• suspension

  • separates into layers over time

  • particle are trapped by filters and can scatter light

  • oil and water, dirt and water, orange juice

• colloid

  • particles never settle out

  • scatter light = Tyndall effect

  • gel, fog

how do you find density?

• D = m/v

• solids —> g/cm³

• liquids —> g/mL

• round to sig fig

how do you find volume with formula and water displacement?

• volume found by multiplying height, width, and length

• subtract amount of water by how much it rose

what is the formula for percent error?

percent error = (experimental value - accepted value) / (accept value) * 100

review the scientists and their experiments.

review !!

know this

what is the atomic number?

• # of protons in each atom of a given element

• unique to each elements and does not change

• tells # of electrons for the elements if the element is neutral

protons = ___ or ___

electrons or mass number

what is an isotope?

• amount of protons and electrons are constant in all neutral atoms of an element, but the # of neutrons can vary

• atoms of the same element that have different # of neutrons

what are ions?

• typically in an atom, the electron can change the # of protons and neutron do not change especially in chemical reactions

• gained or lost electron therefore they have a charge

• cation: lost (+)

• anion: gained (-)

what is a Bohr model?

• focused on electron

• count # of electrons and place in energy levels

what changes in an atom and what stays the same for chemical reactions?

• the electrons in the outer shells of atoms are rearranged

• the number of protons and neutrons in the nucleus stays the same

what is unique for each element? what is the most common isotope for each element? why does an element have a positive or negative charge?

• it has a specific number of protons in its nucleus, called its atomic number

• most common isotope of an element is the one that has the most stable nucleus

• an element gets a positive charge if it loses electrons or a negative charge if it gains electrons

how do you calculate average atomic mass?

(mass * percent) + (mass * percent) …

what are the conversion formulas for Celsius, Fahrenheit, and Kelvin?

• F = (C * 1.8) + 32

• C = (F - 32)/1.8

• K = C + 273.15

identify the masses of various subatomic particles and tell where the atom gets most of its weight/mass.

• almost all of an atom’s weight comes from the protons and neutrons in the nucleus

what is the difference between accuracy and precision?

• accuracy is how close a measurement is to the actual value

• precision is how close together a group of measurements are

how is science and philosophy different?

• science uses experiments and observations to test ideas about the natural world

• philosophy uses reasoning and logic to explore questions about existence, knowledge, and meaning.