Chemistry Test 1&2 Study Guide

Which three phase changes are exothermic?

freezing, condensation, deposition

During a phase change, a substance undergoes a(n)

reversible change from one state to another

Which technique is used to separate homogeneous solutions?

Distillation

What type of chemist would regulate the rate of gasoline burning in an engine?

Physical Chemist

Air is a solution

True

Which of the following is a mixture?

Air

Which of the following phrases describes a heterogeneous mixture?

Composition varies

‼️‼️‼️The symbol for the element potassium is

K

Which of the following is NOT a possible clue that a chemical change is taking place?

A change of state

The name of a science fair project is "Does Calcium Help Tomato Plants Produce More Tomatoes". What is the manipulated variable?

Amount of calcium added to soil

What type of chemist would determine the composition of a moon rock?

Analytical Chemist

‼️‼️‼️What is the smallest particle of an element?

Atom

What type of chemist would develop a new type of wheat seed?

Biochemist

Water can evaporate, how is evaporation different from boiling water?

lower temperature and only at the surface

What is the difference between a hypothesis and a theory?

"A hypothesis is a proposed explanation for an observation." "A theory is a well-tested explanation for a broad set of observations." A hypothesis is a PROPOSED explanation for 1 or a few observations. A theory has been tested, and is an explanation for the observations during a series of tests.

List the steps of solving numeric problems.

"The steps for solving a numeric word problem are analyze, calculate, and evaluate." 1. Analyze: To solve a word problem, you must first determine where you are starting from (identify what is known) and where you are going (identify what is unknown). What is known may be a measurement or an equation that shows a relationship between measurements. If you expect the answer (the unknown) to be a number, you need to determine what unit(s) the answer should have before you do any calculations. After you identify the known and the unknown, you need to make a plan for using what is known to arrive at the unknown. Planning is at the heart of successful problem solving. 2. Calculate: If you make an effective plan, doing the calculations is usually the easiest part of the process. 3. Evaluate: After you calculate an answer, you should evaluate it. Is the answer reasonable? Does it make sense? If not, reread the word problem. Did you copy the data correctly? Did you choose the right equations?

Why are collaboration and communication important in science?

"When scientists collaborate and communicate with one another, they increase the likelihood of a successful outcome. —Collaboration-Scientists choose to collaborate for different reasons. For example, some research problems are so complex that no one person could have all the knowledge, skills, and resources to solve the problem. It is often necessary to bring together individuals from different disciplines. Each scientist will typically bring different knowledge and, perhaps, a different approach to a problem. " —Communication- The way scientists communicate with each other and with the public has changed over the centuries. In earlier centuries, scientists exchanged ideas through letters. They also formed societies to discuss the latest work of their members. When societies began to publish journals, scientists could use the journals to keep up with new discoveries." —Collaborating and Communicating allows scientists to share ideas.

Study the matter diagram - give examples of each type of matter and know how to differentiate between the following: elements and compounds; homogeneous and heterogeneous mixtures.

-elements and compounds- • compound- a substance that contains two or more elements chemically combined in a fixed proportion. A compound is a substance that contains two or more elements chemically combined in a fixed proportion. • element- the simplest form of matter that has a unique set of properties; an element cannot be broken down into simpler substances by chemical means. - homogeneous mixtures and heterogeneous mixtures • heterogeneous mixture- a mixture that is not uniform in composition; components are not evenly distributed throughout the mixture. • homogeneous mixture- a mixture that is uniform in composition; components are evenly distributed and not easily distinguished.

Be able to define and determine the independent (manipulated) variable, the dependent (responding) variable, and the controlled variable in an experiment.

-manipulated variables- the variable that is changed during an experiment; also called independent variable. -responding variables- the variable that is observed during an experiment; also called the dependent variable. -controlled variable- the variable(s) that remain the same throughout the experiment for all samples

List and define the steps of the scientific method.

1⃣Making observations- stating relationships; information obtained through the senses; observation in science often involves a measurement. 2⃣Proposing/Testing hypothesis- a proposed explanation for an observation. 3⃣Experiment- a repeatable procedure that is used to test a hypothesis; -manipulated variables- the variable that is changed during an experiment; also called independent variable. -responding variables- the variable that is observed during an experiment; also called the dependent variable. 4⃣Developing theories- a well-tested explanation for a broad set of observations 5⃣Forming scientific law- a concise statement that summarizes the results of many observations and experiments

a dark cloth is faded by the sun

Chemical Change

bread is toasted

Chemical Change

‼️‼️Which of these groups of letters could be used as a symbol for a naturally occurring element?

Cm

takes the volume and shape of its container

Gas

‼️‼️Which of the following was a major contribution to chemistry by Antoine Lavoisier?

He showed that oxygen is required for material to burn.

Which of the following statements does NOT apply to a compound?

It can be separated into components by physical methods.

Know how Lavoisier changed the science of chemistry.

Lavoisier helped transform chemistry from a science of observation to the science of measurement that it is today. The Lavoisiers tested hypothesis using scales and microscopes. The Law of Conservation of Mass. Burning. https://www.youtube.com/watch?v=QiiyvzZBKT8 "In France, Antoine-Laurent Lavoisier did work in the late 1700s that would revolutionize the science of chemistry. Lavoisier helped to transform chemistry from a science of observation to the science of measurement that it is today. To make careful measurements, Lavoisier designed a balance that could measure mass to the nearest 0.0005 gram. One of the many things Lavoisier accomplished was to settle a long-standing debate about how materials burn. The accepted explanation was that materials burn because they contain phlogiston, which is released into the air as a material burns. To support this explanation, scientists had to ignore the evidence that metals can gain mass as they burn. By the time Lavoisier did his experiments, he knew that there were two main gases in air—oxygen and nitrogen. Lavoisier was able to show that oxygen is required for a material to burn. Lavoisier's wife Marie Anne, shown in the figure, helped with his scientific work. She made drawings of his experiments and translated scientific papers from English."

has a definite volume but an indefinite shape

Liquid

Which of the following would be described as an extensive property of matter?

Mass (volume is too)

‼️Matter is anything that has ____.

Mass and occupies space

Which of these steps of the scientific method involves stating a relationship but not proposing an explanation for the relationship?

Observation

gasoline boils

Physical Change

soap is mixed with water

Physical Change

️a puddle dries up in the sun

Physical Change

Which of the following is a chemical reaction?

Rusting of iron

Which of these materials is the best example of a heterogeneous mixture?

Sand

has a definite shape and volume

Solid

Which of the following can be separated with a filter?

Suspensions

Biochemistry involves the study of living organisms

True

Low levels of lead in the blood can permanently damage the nervous system.

True

Pesticides can kill beneficial insects such as bees.

True

The substances formed in a chemical reaction are called products.

True

Which of the following is the best example of a homogeneous mixture?

Vinegar

Which of these substances is a compound?

Water

Chemical Reaction

a change in which one or more reactants change into one or more products; characterized by the breaking of bonds in reactants and the formation of bonds in products. "During a chemical change, the composition of matter always changes. When the charcoal is heated and burned, a chemical change occurs. The substances in charcoal react with oxygen in the air to form other substances. A chemical change is also called a chemical reaction. One or more substances change into one or more new substances during a chemical reaction. A substance present at the start of the reaction is a reactant. A substance produced in the reaction is a product. In the burning of charcoal, carbon and oxygen are the main reactants, and carbon dioxide is the main product."

Mass

a measure of the amount of matter that an object contains; the SI base unit of mass is the kilogram. "Recall that matter is anything that has mass and takes up space. The mass of an object is a measure of the amount of matter the object contains. The mass of a basketball is greater than the mass of a golf ball. There is also a difference in the volume of the balls. The volume of an object is a measure of the space occupied by the object. The volume of the basketball is greater than the volume of the golf ball. Mass and volume are both examples of extensive properties. An extensive property is a property that depends on the amount of matter in a sample."

Heterogeneous Mixture

a mixture that is not uniform in composition; components are not evenly distributed throughout the mixture. "In chicken noodle soup, the ingredients in the soup are not evenly distributed throughout the mixture. There is likely to be different amounts of chicken and noodles in each spoonful. A mixture in which the composition is not uniform throughout is a heterogeneous mixture."

Homogeneous Mixture

a mixture that is uniform in composition; components are evenly distributed and not easily distinguished. "The substances in olive oil are evenly distributed throughout the mixture. So, olive oil doesn't look like a mixture. The same is true for vinegar. Vinegar is a mixture of water and acetic acid. Olive oil and vinegar are homogeneous mixtures. A homogeneous mixture is a mixture in which the composition is uniform throughout. Another name for a homogeneous mixture is a solution. Many solutions are liquids. But some are gases, like air, and some are solids, like stainless steel, which is a mixture of iron, chromium, and nickel."

Distillation

a process used to separate components of a mixture using differences in boiling points. "Tap water is a homogeneous mixture of water and substances that are dissolved in the water. One way to separate water from the other components in tap water is through a process called distillation. During a distillation, a liquid is boiled to produce a vapor that is then condensed into a liquid. The figure shows an apparatus that can be used to perform a small-scale distillation. As water in the distillation flask is heated, water vapor forms, rises in the flask, and passes into a glass tube in the condenser. The tube is surrounded by cold water, which cools the vapor to a temperature at which it turns back into a liquid. The liquid water is collected in a second flask. The solid substances that were dissolved in the water remain in the distillation flask because their boiling points are much higher than the boiling point of water."

Reactant

a substance present at the start of a reaction. "A chemical change is also called a chemical reaction. One or more substances change into one or more new substances during a chemical reaction. A substance present at the start of the reaction is a reactant. A substance produced in the reaction is a product. In the burning of charcoal, carbon and oxygen are the main reactants, and carbon dioxide is the main product."

product

a substance produced in a chemical reaction. "A chemical change is also called a chemical reaction. One or more substances change into one or more new substances during a chemical reaction. A substance present at the start of the reaction is a reactant. A substance produced in the reaction is a product. In the burning of charcoal, carbon and oxygen are the main reactants, and carbon dioxide is the main product."

Compound

a substance that contains two or more elements chemically combined in a fixed proportion. A compound is a substance that contains two or more elements chemically combined in a fixed proportion. For example, carbon, oxygen, and hydrogen are chemically combined in the compound sucrose. Sometimes sucrose is called table sugar to distinguish it from other sugar compounds. In every sample of sucrose, there are twice as many hydrogen particles as oxygen particles. The proportion of hydrogen particles to oxygen particles in sucrose is fixed. There is a key difference between elements and compounds. Compounds can be broken down into simpler substances by chemical means, but elements cannot."

Phase

any part of a sample with uniform composition and properties "The term phase is used to describe any part of a sample with uniform composition and properties. By definition, a homogeneous mixture consists of a single phase. A heterogeneous mixture consists of two or more phases. When oil and vinegar are mixed, they form a heterogeneous mixture with two layers, or phases. As shown in the figure, the oil phase floats on the vinegar phase."

Which of the following is not a physical change?

burning gasoline in an engine

Vapor

describes the gaseous state of a substance that is generally a liquid or solid at room temperature. "The words vapor and gas are sometimes used interchangeably. But there is a difference. The term gas is used for substances, like oxygen, that exist in the gaseous state at room temperature. (Gaseous is the adjective form of gas.) Vapor describes the gaseous state of a substance that is generally a liquid or solid at room temperature, as in water vapor."

What is the phase change called from a solid to a gas?

sublimating

Element

the simplest form of matter that has a unique set of properties; an element cannot be broken down into simpler substances by chemical means. An element is the simplest form of matter that has a unique set of properties. Oxygen and hydrogen are two of the more than 100 known elements. There is a key difference between elements and compounds. Compounds can be broken down into simpler substances by chemical means, but elements cannot.

List the three states of matter and the shape/volume properties of each.

—A solid is a form of matter that has a definite shape and volume. Molecules are close together and have lower energy. Not easily compressed. —A liquid is a form of matter that has an indefinite shape, flows, yet has a definite volume. Molecules are further apart and slide past each other. Not easily compressed. —A gas is a form of matter that takes both the shape and volume of its container. Molecules are very far apart and move rapidly. Indefinite shape/volume. Easily compressed.

Review the signs that a chemical reaction has occurred that you observed in lab.

—A transfer of energy —A change in color —The production of a gas (without heating) —The formation of a solid (scientists call this a precipitate)

List the six physical changes and know which ones are endothermic and which are exothermic.

—Endothermic (low to high energy): Vaporization- liquid to gas Melting (Fusion)- solid to liquid Sublimation- Solid to gas —Exothermic (high to low energy): Condensation- gas to liquid Freezing- liquid to solid Deposition- gas to solid

mixture

A physical blend of two or more substances that are not chemically combined. A mixture is a PHYSICAL, not chemical, blend of two or more components.Based on the distribution of their components, mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures. A mixture in which the composition is not uniform throughout is a heterogeneous mixture. A mixture in which the composition is uniform throughout is a homogeneous mixture. Another name for a homogeneous mixture is a solution.

Know how to write the symbols and formulas for elements and compounds.

All natural elements have a one or two letter symbol. The first letter is always capitalized and the second letter is always lowercase, and smaller. All synthetic elements have a three letter symbol, the first letter is capitalized and the second and third are both lowercase. Compound Formulas are written with the symbols of the elements that make them up. A subscript number after an element indicates how many atoms of that element there are in that compound.

During any chemical change, the mass of the products is

Always equal to the Mass of the reactants

Define a chemical and a physical change - give examples of each.

Chemical Change- a change that produces matter with a different composition than the original matter. Burn, rot, rust, decompose, ferment, corrode, explode. Physical Change-a change during which some properties of a material change, but the composition of the material does not change. Slicing bread, evaporation, condensation etc.

Carbon dioxide plus water forms carbonic acid. Water and carbonic acid are products of this reaction.

False: water is a reactant

Organic chemistry is the study of chemicals that contain oxygen.

False: Carbon

The study of the rate and energy transfer of reactions is the study of inorganic chemists.

False: Physical Chemists

Insecticides help control weeds in crops.

False: herbicides control weeds; insecticides control insects

‼️‼️‼️The temperature at which a substance freezes is lower than the temperature at which it melts.

False: it is the same

Suspensions have the smaller particles than colloids and solutions

False: larger

Macroscopic objects can be seen only under magnification.

False: microscopic

Cotton was invented by a chemist.

False: nylon, Kevlar, Lycra

A colloid will reflect light and the particles will settle, or separate.

False: particles will not settle

Fossil fuels are material found in air, water, or soil that is harmful to humans or other organisms.

False: pollutants

The goal of applied chemistry is to accumulate knowledge.

False: solve a problem