chemistry midterm

Compounds and elements

The two types of matter that are pure substances are _______ and ____.

Sn

Tin

Analytical

Two scientists are trying to determine the exact nature of the chemicals in a lava flow. They are working in the field of ___ chemistry.

elements in same group have similar properties. Because Xenon and Helium are in the same group, they have similar properties.

What can you predict about the properties of xenon and helium, both in Group 18 in the periodic table? Why?

Variants of a particular chemical element

What is an isotope?

count of how many protons an atom has in its nucleus

What is the atomic number of an atom?

total # of neutrons and protons in the nucleus

What is the mass number of an atom?

Kg.

What is the most appropriate SI unit for expressing the mass of a dog?

Inorganic

A chemistry student is studying the formation of quartz crystals. She is studying ____ chemistry.

Liquid

A sample of matter can be poured from container to container. It takes the shape of its container but only takes up a certain volume. Based on this information, the sample is in the ____ state.

Analytical

A scientist is using mathematical models to isolate a new chemical process. He is working in the field of ____ chemistry.

Physical

A scientist is working to determine the properties and changes of matter and their relation to energy of a newly discovered mineral. She is working in the field of ____ chemistry.

Organic

A scientist is working to develop better dating methods for substances that contain carbon. He is working in the field of _____ chemistry.

Bio

A team of scientists is working to discover how an enzyme affects blood cells in sheep. They are working in the field of ___ chemistry.

Aluminum

Al

homogenous

An alloy such as a gold ring is an example of a(n) ______ mixture.

Chemical

An apple turning brown after being cut is an example of a _____ change.

Chemical

Any substance with a definite composition is a ______.

Problem

Applied research is often performed to find the answer to a particular ______.

Knowledge

Basic research is performed to increase ____.

Bismuth

Bi

Cl

Chlorine

Theory - broad generalization that explains a body of facts or phenomena (before conclusion) Hypothesis - testable statement (after testing & question)

Define the terms theory and hypothesis in a way that shows the role of each in the scientific method.

made of 2 kinds of particles, protons, and neutrons

Describe the nucleus of an atom.

Qualitative - non-numerical info. Quantitative- numerical info.

Difference between qualitative and quantitative observations.

Atoms in a molecular compound share electrons to achieve stability. Atoms in an ionic compound gain or lose electrons to form ions, which combine so that the number of positive and negative charges is equal.

Differentiate between an ionic compound and a molecular compound.

Copper, Water - reactants (original substance) Copper (II) Oxide, Hydrogen - products (resulting substance)

Differentiate between the reactants and the products in the reaction represented by the equation---copper + water ---> copper(II) oxide + hydrogen.

Mass - measure of the quantity of matter Weight - measure of the gravitational pull on matter

Distinguish between mass and weight.

Precision - the exactness of a measurement Accuracy - how close a measurement is to the true value of the quantity measured

Distinguish between precision and accuracy.

1s2 2s2 2p2

Electron configuration for nitrogen, atomic number 7.

A homogeneous mixture can be separated by physical means, while a pure substance cannot. For example, salt can be removed from a saltwater mixture by evaporating the water, but to separate water into hydrogen and oxygen requires electrolysis, a chemical means

Explain the difference between a pure substance and a homogeneous mixture. Use an example in your answer.

Because to observe either, a chemical change, burning, must occur.

Explain why flammability and combustibility are chemical properties.

Any substance w/ a definite composition is a chemical; some substances that have definite compositions may be hazardous but most are not. water and oxygen

Explain why it is incorrect to assume that all chemicals are potentially dangerous or hazardous. Give two examples of chemicals that are necessary for human life.

Ar

Find the symbol for the element argon.

relative charge = +1 location = nucleus

Give the location and relative charge of a proton.

Heterogeneous

Gravel is an example of a(n) _____ mixture.

Hydrogen

H

He

Helium

nonmetal, brittle, poor conductor of heat and electricity

I

prefix k by factor of 1000 prefix c by factor of 0.01

Identify 2 prefixes that can be added to an SI base unit to change its magnitude. For each prefix, tell how the magnitude changes.

Products

In a bonfire, oxygen allows wood to combust, leaving behind ashes. In this process, oxygen and wood are the reactants, and the ashes are the ______.

Melted - physical, didnt change identity burned - chemical, changed identity

In one experiment, magnesium metal is melted. In a second experiment, magnesium metal is burned. Classify the change in each experiment as chemical or physical. Explain your reasoning.

P and S are nonmetals - most similar Na is metal

In terms of the periodic law, explain which two of these elements are most similar: sodium (element 11), phosphorus (element 15), and sulfur (element 16).

14

In which group can you find the element carbon?

1

In which group can you find the element lithium?

18

In which group can you find the element neon?

10

In which group can you find the element nickel?

7

In which period can you find the actinide series?

6

In which period can you find the element gold?

4

In which period can you find the element iron?

6

In which period can you find the lanthanide series?

I

Iodine

Chemical

Iron and sulfur, when heated, form an iron sulfide that has different properties from either iron or sulfur. The formation of iron sulfide is an example of a _____ change.

mass cannot be created nor destroyed in ordinary chemical and physical changes

Law of Conservation

the statement that a chemical compound always contains the same elements in exactly the same proportions, regardless of the size or the source of the sample

Law of Definite Proportions.

When 2 elements combine to form 2 or more compounds, the mass of one element that combines with a given mass of the other in the ratio of small whole #'s

Law of Multiple Proportions

Gaseous

Matter that has neither a definite volume nor a definite shape is in the _____ state.

Magnesium

Mg

Filtration, vaporized, or distillation

Name 3 ways that mixtures might be separated.

Ne

Neon

Phosphorus

P

Lead

Pb

Metalloids; semiconductors of electricity, less malleable than metals, but not as brittle as nonmetals.

Properties for the elements in period , group 15.

V=m3 Kg/m3 to density or D=kg/m3 or m3 to volume unit

Show how SI units for volume and density are derived from SI base units for length and mass.

Compound

Some iron and sulfur are mixed together, then heated. When the result is cooled, the iron can no longer be separated from the sulfur with a magnet. The result of heating the mixture was the formation of a(n) ______.

metal, malleable, good conductor

Sr

quality of life

Technological development is performed to better our ______.

3 valence electrons in p orbital of 2nd energy level

The electron configuration for nitrogen is 1s2 2s2 2p3. What does the 3 in 2p3 mean?

Physical

The melting of butter is a _____ change because it does not produce any new substances.

Reactants

The oxygen in air causes iron to rust. Iron and oxygen are ____ in this process, and rust is the product.

Liquid state

The particles of a substance in the ____ ____ are able to slide past each other.

Chemistry

The study of matter and changes that occur in matter best describes the science of _______.

The mass # is basically given by finding the average of the most abundant isotope. Also within the mass #, if the # of neutrons is altered that means it becomes another isotope of the element.

What is the relationship between isotopes, mass number, and neutrons?

Physical

When examining a mineral, hardness and color are two of the properties used for identification. Hardness and color are examples of ____ properties.

In both changes, a gas is produced. Water boiling is a physical change because the water vapor has the same chemical properties as the water. In the chemical change, a new substance, carbon dioxide, is formed.

When water boils, steam forms. When vinegar and baking soda combine, carbon dioxide gas is released. Which change is physical, and which is chemical? How do you know?

bromine

Which element has the following electron configuration: [Ar] 4s2 3d10 4p5?

Gas particles do not attract one another, and can easily move from one place to another.

Why can a gas fill the entire volume of its container?

Atoms form chemical bonds to establish a more-stable arrangement. As independent particles, they are at high potential energy. By bonding, they decrease their potential energy, thus becoming more stable.

Why do most atoms form chemical bonds?

[Ne] 3p4

Write the noble-gas electron configuration for silicon.