Explain the main goal of chemistry

Describe Rutherford's nuclear model

1) most of the atom's mass and all of its positive charge are contained in a small core called the nucleus 2) Most of the volume of the atom is empty space, throughout which tiny negatively charged electrons are dispersed 3) There are as many negatively charged electrons outside the nucleus as there are positively charged particles within the nucleus

main ideas of atomic theory

1. elements are composed of tiny, indestructible particles called atoms 2. all atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements 3. atoms combine in simple whole-number ratios to form compounds 4. Atoms of one element cannot change into atoms of another element

Explain the differences between a hypothesis, a law, and a theory

A hypothesis is a tentative interpretation or explanation of an observation. A law is a concise statement that summarizes past observations and predicts future ones. A theory attempts to explain why the observed behavior is happening.

Describe the scientific approach to knowledge. How does it differ from other approaches?

An approach to acquiring knowledge about the natural world that begins with observations and leads to the formation of testable hypotheses. Hypotheses are tested by experiments Which may support a hypothesis or prove it wrong - in which case the hypothesis must be modified or discarded. A series of similar observations can lead to the development of a scientific law. One or more well-established hypotheses may form the basis for a scientific theory. Alternative approaches, such as Plato's attempt to explain reality through reason rather than through observing the real physical world.

What observation did Antoine Lavoisier make? What law did he formulate?

He noticed that when an object was burned in a closed container, there was no change in mass within the container during combustion. Law of conservation of mass: In a chemical reaction, matter is neither created nor destroyed

What are isotopes? What is percent natural abundance of isotopes?

Isotopes are atoms with the same number of protons but different numbers of neutrons. The percent natural abundance is the relative amount of each different isotope in a naturally occurring sample of a given element.

What is wrong with the expression "That is just a theory"

It is generally taken to mean that there is no scientific proof behind it, which is the opposite of the meaning of a theory, which are tested again and again.

how and by whom was the electron discovered? what basic properties of the electron were reported with its discovery?

JJ Thomson performed experiments to probe the properties of cathode rays.

What are the three kinds of temperature scales? Does the size of a degree differ among them?

Kelvin Celsius Fahrenheit K and C degrees are same size (1.8x F)

history of atomic idea

Leucippus and democritus first proposed matter was composed of small indestructible particles. John Dalton then offered convincing evidence. important laws: conservation of mass, law of definite proportions, law of multiple proportions.

What are two different ways to classify matter?

Matter can be classified by its state - solid, liquid, or gas - or according to its composition

How is distillation used to separate mixtures

Mixtures of miscible liquids can usually be separated by distillation. The more volatile liquid is boiled off.

difference of physical change and chemical change

Physical changes change only state or appearance, not composition. Chemical changes change composition.

Physical Property vs Chemical

Physical: One that a substance displays without changing its composition Chemical: One that a substance displays only by changing composition through chemical change.

How do solids, liquids, and gases differ?

Solid: molecules close, don't move around much Liquid: molecules just as close, free to move Gas: molecules spread apart, free to move,

Difference of Z and A

The atomic number Z is the number of protons in an atom's nucleus.

What theory did John Dalton formulate?

The atomic theory of matter ( matter is composed of small indestructible particles called atoms)

Explain the main goal of chemistry

The main goal of chemistry is to seek to understand the behavior of matter by studying the behavior of atoms and molecules

Explain this statement in your own words and give an example: the properties of the substances around us depend on the atoms and molecules that compose them

The specific types of atoms and molecules that compose something tell us a great deal about which properties to expect from a substance. A material compound of only sodium and chloride ions will have the properties of of table salt. If the atoms and molecules change, so do the properties that we expect the material to have.

What is a derived unit?

a combination of other units. (m/s)

pure substance vs mixture

a pure substance is composed of only one kind of atom or molecule a mixture is a substance composed of two or more different kinds of atoms or molecules that can be combined in variable proportions.

What is the difference between a crystalline solid and an amorphous solid?

crystalline: atoms or molecules arranged in patterns with long-range, repeating order. amorphous: atoms or molecules have no long-range order

Difference between density and mass

density is mass/volume mass depends on the amount of substance (extensive)

Rutherford's gold foil experiment

directed positively charged particles at an ultra-thin sheet of gold foil. They should pass through if charge spreads through entire volume of atom. Since some particles didn't pass through, mass and charge must've been concentrated in space smaller than the atom.

element vs compound

element: pure substance that cannot be decomposed into simpler substances. compound: composed of two or more elements in fixed proportions

homogeneous vs heterogenous mixture

homogeneous: same composition throughout heterogeneous: different composition in different regions

intensive vs extensive

intensive properties are independent of amount of substance. Extensive properties are dependent on amount of substance.

What are the standard SI base units of length, mass, time, and temperature?

length: meter (m) mass: kilogram (kg) time: seconds (s) Temperature: Kelvin (K)

significance of law of conservation of energy

matter often exchanges energy with its surroundings, and the total energy is always conserved

what kind of mixtures can be separated by filtration?

mixtures composed of an insoluble solid and a liquid

plum-pudding model of the atom

negatively charged electrons were small particles electrostatically held within a positively charged sphere.

What are prefix multipliers?

prefix multipliers are used with the standard units of measurement to change the value of the unit by powers of 10. Example: kilo, micro

what defines an element

the number of protons in the nucleus defines the identity of an element