Chemistry 2023 Exam

What is chemistry?

What is chemistry?

the study of the composition, structure, and properties of matter, the processes that matter undergoes, and the energy changes that accompany these processes

What is mass?

A measure of the amount of matter in an object

What is matter?

Anything that has mass and takes up space

What is an atom?

the smallest unit of an element that maintains the chemical identity of that element

What is an element?

pure substance that consists entirely of one type of atom, and it cannot be broken down into simpler substances

What is a compound?

a substance that can be broken down into simple stable substances and is made of 2 or more chemically bonded elements

What are extensive properties?

properties that depend on the amount of matter that is present ex. mass, volume, length

What are intensive properties?

properties that do not depend on the amount of matter present ex. density, temperature, color, boiling point

What is a physical change?

a change of matter from one form to another without a change in chemical properties

What is a chemical change?

Changing of one substance into a new substance that has different properties

Is frying an egg a physical or chemical change?

chemical change

Is sharpening a pencil a physical or chemical change?

physical change

Is an ice cube melting a physical or chemical change?

physical change

is a leaf changing colors a physical or chemical change?

chemical change

Is iron rusting a physical or chemical change?

chemical change

What happens during a chemical reaction?

reactants come to together to form products

Differentiate between a mixture and a pure substance.

A mixture is a combination of two or more substances that are physically mixed but not chemically bonded, and can be easily separated by physical means. A pure substance is a substance with a constant composition and distinct properties, either an element or compound.

What is a homogeneous mixture?

a mixture in which the composition is uniform throughout

What is a heterogeneous mixture?

a mixture in which the composition is not uniform throughout

Is saltwater a homogeneous or heterogeneous mixture?

homogeneous

Is Kool-Aid a homogeneous or heterogeneous mixture?

homogeneous

Is garden salad a homogeneous or heterogeneous mixture?

heterogeneous

Is clay and water a homogeneous or heterogeneous mixture?

heterogeneous

Is granite a homogeneous or heterogeneous mixture?

heterogeneous

Is air a homogeneous or heterogeneous mixture?

homogeneous

Is Italian salad dressing heterogeneous or homogeneous mixture?

heterogeneous

What is a change in state?

the transition of matter from one physical form into another ex. solid to liquid

Is a change of state a physical or chemical change? Why?

Physical, because it involves a transformation into a physical form of matter without altering its chemical composition (no new substance formed).

What are some indicators that a chemical reaction has occured?

heat is released or absorbed, light is given off, gas has formed (odor, bubbles), precipitate (solid) formed, or a color change

What is a mixture?

A combination of two or more substances that are not chemically combined

What is a pure substance?

A single element or compound, not mixed with any other substance

Is water an element, compound, mixture, or pure substance? List all that apply.

compound and pure substance

Is orange juice with pulp an element, compound, mixture, or pure substance? List all that apply.

mixture

Is potassium an element, compound, mixture, or pure substance? List all that apply.

element and pure substance

Is salt an element, compound, mixture, or pure substance? List all that apply.

compound and pure substance

Is lead an element, compound, mixture, or pure substance? List all that apply.

element and pure substance

Is sand an element, compound, mixture, or pure substance? List all that apply.

mixture

In the lab we separated purple Kool-Aid into red and blue dyes. Was this a physical change or a chemical change? Why?

Physical, because we separated a mixture of blue and red dyes. Mixtures can be separated without chemical reactions.

What is volume?

The amount of space an object takes up

Calculate the density of an object having a mass of 8.4 grams and a volume of 3.1 cm³.

2.71 g/cm³

Diamond has a density of 3.26 g/cm³. What is the mass of a diamond that has a volume of 0.351 cm³?

1.14 g

Find the volume of a substance having a density of 22.4 g/mL and a mass of 5.3 grams.

0.24 mL

When a marble is placed in a graduated cylinder, the water level rises from 12 mL to 14 mL. Find the density of the marble if the mass of the marble is 4 grams.

2 g/mL

What do you know about density if an object 1) sinks? 2) floats? 3) stays suspended in the liquid?

1. greater density than liquid 2) less density than liquid 3) same density as liquid

A student finds the density of a substance to be 40.53 g/mL. The accepted value of the density is 42.12 g/mL. Find the percentage error.

3.77%

In the lab, you measure the density of water to be 1.6 g/mL. You look up the density of water online and find several reliable sources that say that the density of water is 1.00 g/mL. Calculate your percent error.

60%

Write the following in scientific notation: 6,780,000

6.78 x 10⁶

Write the following in scientific notation: 0.000986

9.86 x 10⁻⁴

Write the following in scientific notation: 345.12

3.45 x 10²

Write the following in scientific notation: 7.34

7.34 x 10⁰

Write the following in standard notation: 1.34 x 10³

1340

Write the following in standard notation: 4.21 x 10⁻⁵

0.0000421

Write the following in standard notation: 4.32 x 10¹

43.2

Write the following in standard notation: 3.91 x 10⁻²

0.0391

What is the Law of Conservation of Mass/Matter?

matter cannot be created or destroyed

What is the law of definite proportions?

a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound

What is the Law of Multiple Proportions?

if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

What are the five points of Dalton's Atomic Theory?

1. All matter is composed of atoms

2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties

3. Atoms cannot be subdivided, created, or destroyed

4. Atoms of different elements combine in simple whole number ratios to form chemical compounds

5. In chemical reactions, atoms are combined, separated, or rearranged.

Differentiate between an orbit and an orbital.

An orbit is a fixed path along which electrons revolve around the atom's nucleus, while an orbital is an area used to calculate the probability of finding any electron.

Who is J.J Thompson?

scientists who concluded that all cathode rays are composed of identical negatively charged particles (discovered electrons doing the Cathode Rays experiment)

What is the plum pudding model?

Proposed by Thomson, model that predicted that negative electrons were spread evenly throughout the positive charge of the rest of the atom.

What did Rutherford discover?

Experiments by Rutherford and his associates in which a piece of gold foil was bombarded with alpha particles that led to the discovery of the nucleus

Where is most of the mass of an atom found?

nucleus

Where is most of the volume of an atom found?

electron cloud

Where are protons located and what is it's charge?

nucleus, positive (+1)

Where are neutrons located and what is it's charge?

nucleus, zero

Where are electrons located and what is it's charge?

electron cloud, negative (-1)

What does the atomic number tell you?

the number of protons in an atom

Isotopes have differing numbers of _________.

neutrons

Ions have differing numbers of ___________.

electrons

What is the mass number?

the total number of protons and neutrons in an atom

How many valence electrons does Si have?

4

How many valence electrons does Al have?

3

How many valance electrons does Cl have?

7

How many valence electrons does K have?

1

How many valence electrons does O have?

6

Predict the charge an bromine ion would have?

-1

Predict the charge that a calcium ion would have.

+2

Predict the charge that a lithium ion would have.

+1

Predict the charge a boron ion would have.

+3

Predict the charge a sulfur ion would have.

-2

Predict the charge a neon ion would have.

0

Find the mass in grams of 4.3 moles of nitrogen.

60.24 gN

Find the number of moles of calcium in 9.0 grams of calcium.

0.22 molCa

Find the number of molecules in 45.0 grams grams of water.

1.5 x 10²⁴ moleculesH₂O

Convert 46.3 grams of RbNO₃ to moles.

0.31 molRbNO₃

Convert 2.7 moles of copper to grams.

172 or 171.59 gCu

Convert 7.5 x 10¹⁵ atoms of carbon to moles.

1.25 x 10⁻⁸ or 1.3 x 10⁻⁸ molC

How many formula units are in 35.10 grams of Al₂(SO₄)₃

6.18 x 10²² formula unitsAl₂(SO₄)₃

What is the average atomic mass?

the weighted average of the atomic masses of the naturally occurring isotopes of an element

Calculate the average atomic mass of copper. There are two isotopes of copper: copper-63 with a 69.15% natural abundance and copper-65 with a 30.85% natural abundance.

63.62

Which isotope of carbon is most abundant on earth? There are three carbon isotopes: carbon-12, carbon-13, and carbon-14.

Carbon-12, because the average atomic mass on the periodic table is 12.01 meaning the most abundant carbon found are carbon-12.

What is electromagnetic radiation?

a form of energy that exhibits wavelike behavior as it travels through space

What is the EM Spectrum?

all the types of electromagnetic radiation together

What is wavelength?

the distance between corresponding points on adjacent waves (λ)

What is frequency?

the number of waves that pass a give point in a specific amount of time, usually one second (ν)

What is the photoelectric effect?

The emission of electrons from a metal when light shines on the metal

What is a quantum?

the minimum quantity of energy that can be lost or gained by an atom

What is ground state?

The lowest energy state of an atom

What is excited state?

A state in which an atom has a higher potential energy than it has in its ground state