Chem 101 Week 2
When a physical change is observed: Select the correct answer below: it means a chemical property has changed it means a physical property has changed the substance cannot have also undergone a chemical change the substance must have also undergone a chemical change
Correct answer: it means a physical property has changed An observed physical change corresponds to a change in a physical property like phase, hardness, or density. Physical changes can be caused by chemical changes, but are not necessarily indicative of a chemical change.
An example of homogeneous mixture is: Select the correct answer below: muddy water pure water ice water saline water
Correct answer: saline water A homogeneous mixture has uniform composition for any given sample. A saline water solution has equal parts of salt dissolved throughout. Muddy water and ice water are heterogenous mixtures while pure water is a compound (and a pure substance).
All of the following are considered pure substances, EXCEPT: Select the correct answer below: water gold silver soil
Correct answer: soil Soil is not considered a pure substance. A pure substance is a homogeneous substance that has a constant composition. The composition of soil varies from sample to sample.
All of the following are physical properties EXCEPT: Select the correct answer below: texture density toxicity boiling point
Correct answer: toxicity All of the above are physical properties EXCEPT toxicity. Physical properties are characteristics of matter that can be seen about a substance without changing that substance's chemical composition.
Which of the following CANNOT be classified as a compound? Select the correct answer below: carbon dioxide sodium chloride lithium sugar
Correct answer: lithium Lithium is an element. The rest are made of multiple elements.
Homogeneous Mixture Definition
A homogeneous mixture is a mixture of substances blended so thoroughly that you cannot see individual substances. Every sample of the mixture will show the same amounts of each substance. Homogeneous mixtures can be solid, liquid, gas, or plasma mixtures. Properties Of Homogeneous Mixtures Homogeneous mixtures have several identifying properties: Homogeneous mixtures that are thoroughly mixed down to the level of molecules are called solutions. Homogeneous mixtures exist in one phase of matter at a time. You will not see liquid water and solid water together in a homogeneous mixture. That means your glass of ice water, with ice cubes floating in it, is a heterogeneous mixture of homogeneous mixtures. Homogeneous mixtures cannot be expressed as chemical formulas. To describe any homogeneous mixture accurately, you need to name the components and tell their proportion or ratio within the mixture. Like all mixtures, homogeneous mixtures can be separated into their components, usually by taking advantage of their physical properties such as boiling point or magnetism. Saltwater is an example of a homogeneous mixture that can be easily separated by evaporation.
A large change in temperature (not resulting from external heating) with the appearance of gas bubbles is most likely an indication of: Select the correct answer below: a chemical change only physical changes occurring molecules are undergoing physical changes none of the above
Correct answer: a chemical change A large change in temperature with the appearance of gas bubbles indicates that a chemical change has most likely occurred.
Which is an example of a homogeneous mixture? Select the correct answer below: air breakfast cereal soil oxygen
Correct answer: air Air is an example of a homogeneous mixture, oxygen is an element and the remaining options are heterogenous mixtures.
Which of the following states of matter can exert pressure? Select the correct answer below: solid liquid gas all of the above
Correct answer: all of the above All the phases of matter can exert pressure.
Which of the following can only consist of only one kind of atom? Select the correct answer below: an element a pure substance a compound a mixture
Correct answer: an element Elements consist of only one kind of atom. Compounds and mixtures consist of more than one type of atom. A pure substance is either an element or a compound, so it could consist of one type of atom, but it does not have to.
What can be observed without changing the composition of matter? Select the correct answer below: flammability reactivity boiling point toxicity
Correct answer: boiling point A physical property can be observed without changing the composition of matter. Flammability, toxicity, and reactivity are all chemical properties, whereas boiling point is a physical property.
Which of the following is an example of a heterogenous mixture? Select the correct answer below: gasoline air a sports drink salad dressing
Correct answer: salad dressing Salad dressing is an example of a heterogenous mixture as it has a varied composition throughout. The remaining choices are homogeneous mixtures as taking any sample of them would result in a uniform composition from each sample.
Which of the following is NOT a physical property of a piece of paper? Select the correct answer below: the shape of the paper the color of the paper that it burns readily that it can be readily crumpled up
Correct answer: that it burns readily Burning is a combustion reaction, in which chemistry is occurring, so the ability of paper to burn is an example of a chemical property.
Heterogenous mixture
A heterogeneous mixture is a mixture with a non-uniform composition. The composition varies from one region to another with at least two phases that remain separate from each other, with clearly identifiable properties. If you examine a sample of a heterogeneous mixture, you can see the separate components. In physical chemistry and materials science, the definition of a heterogeneous mixture is somewhat different. Here, a homogeneous mixture is one in which all components are in a single phase, while a heterogeneous mixture contains components in different phases. Examples of Heterogeneous Mixtures Concrete is a heterogeneous mixture of an aggregate: cement, and water. Sugar and sand form a heterogeneous mixture. If you look closely, you can identify tiny sugar crystals and particles of sand. Ice cubes in cola form a heterogeneous mixture. The ice and soda are in two distinct phases of matter (solid and liquid). Salt and pepper form a heterogeneous mixture. Chocolate chip cookies are a heterogeneous mixture. If you take a bite from a cookie, you may not get the same number of chips as you get in another bite. Soda is considered a heterogeneous mixture. It contains water, sugar, and carbon dioxide, which forms bubbles. While the sugar, water, and flavorings may form a chemical solution, the carbon dioxide bubbles are not uniformly distributed throughout the liquid.
Which of the following can be broken down into elements by chemical means? Select the correct answer below: an element an atom a compound a mixture
Correct answer: a compound A compound can be broken down into two or more elements by chemical means. An element and atom are already in their most simple forms and cannot be broken down further. A mixture can be separated by physical changes rather than chemical.
A(n) ________ change occurs as a result of a chemical reaction. Select the correct answer below: electrical chemical physical kinetic
Correct answer: chemical A chemical change occurs as a result of a chemical reaction. A chemical change always produces one or more types of matter that differ from the matter present before the change.
Which of the following is a physical change? Select all that apply: chopping wood bending metal cutting a cake frying an egg
Correct answer: chopping wood bending metal cutting a cake Chopping wood, bending metal, and cutting a cake are all physical changes because the composition of the material isn't chemically changing. Frying an egg changes the chemical composition of the egg and is therefore a chemical reaction.
Which of the following could be considered a chemical change? Select the correct answer below: dew condensing on a leaf mixing sugar in with your tea coal burning water evaporating from a pond on a hot day
Correct answer: coal burning Phase changes and mixing of substances are physical processes. When coal burns, carbon atoms form new chemical bonds to oxygen atoms, which is a chemical process.
Which of the following is a physical property? Select the correct answer below: acidity color flammability corrosiveness
Correct answer: color Color is a physical property, whereas acidity, flammability, and corrosiveness are all chemical properties.
A(n) _______ is a substance with a fixed composition of atoms of two or more different elements that are bonded together. Select the correct answer below: mixture compound solution element
Correct answer: compound A compound is a substance with a fixed composition of atoms of two or more different elements that are bound together. For example, water is a substance composed of two different elements, hydrogen and oxygen, where there is a 2:1 ratio of hydrogen atoms to oxygen atoms. Therefore, water or H2O is a compound.
A molecule comprised of more than one type of atom is called a(n): Select the correct answer below: compound mixture element reactant
Correct answer: compound A mixture is composed of two or more types of matter and can be separated by physical changes. Elements are pure substances that cannot be broken down into simpler substances by chemical changes. And reactants are substances undergoing reaction.
Which of the following is NOT a physical change? Select the correct answer below: copper wire is coiled into a spring food coloring is added to water you blow dry your hair fireworks are set off
Correct answer: fireworks are set off Fireworks utilize chemical reactions to create light and energy, so this is an example of a chemical change.
The image below was captured over a hot mug of coffee on a cold morning. Which state of matter is present in the image? An image of a curling stream of greyish blue steam, like the steam from a cup of coffee, is shown. Select the correct answer below: solid liquid gas
Correct answer: gas The image shows gas or steam rising off a hot mug of coffee. These particles have little or no attraction to each other; thus they spread themselves out as much as possible to fill the space around them.
A substance that has fixed volume, but no fixed shape is a: Select the correct answer below: solid liquid gas None of the above
Correct answer: liquid A liquid, like water, has a specific volume that can be measured, but it will take on the shape of whatever vessel it is stored in--whether it is a pot, a cup, a bathtub, or a swimming pool.
Which physical form of matter has a definite volume, but no definite shape? Select the correct answer below: gas solid liquid solid and gas
Correct answer: liquid Liquid is a physical form of matter that has a definite volume, but no definite shape. A solid has a definite volume and definite shape, and a gas has no definite volume or shape.
Matter that will take the shape of its container, but not expand to fill it is in what phase? Select the correct answer below: solid liquid gas none of the above
Correct answer: liquid Liquids have a definite volume, but no definite shape. This means that they will expand to fit the shape of their container, but not expand to fill it completely.
Which of the following is an example of a homogenous mixture? Select the correct answer below: oil and vinegar salad dressing chocolate chip cookie soil maple syrup
Correct answer: maple syrup Maple syrup is an example of a homogenous mixture. Salad dressing, chocolate chip cookies, and soil are all examples of heterogeneous mixtures.
A __________ contains more than one type of substance as part of its composition. Select the correct answer below: mixture pure substance compound element
Correct answer: mixture A mixture contains more than one type of element or compound. A mixture can be categorized as homogeneous or heterogeneous depending on whether it has a uniform composition or not.
How does a mixture differ from a pure substance? Select the correct answer below: pure substances are easily separated into components, mixtures are not mixtures all have uniform compositions, pure substances do not pure substances have constant chemical and physical properties while mixtures are varied mixtures require chemical methods of separation while pure substances can be separated by physical means
Correct answer: pure substances have constant chemical and physical properties while mixtures are varied Mixtures can be classified as homogenous or heterogenous and can be separated into their component parts by chemical or physical means. Pure substances have constant chemical and physical properties while mixtures can be varied.
What physical state of matter is associated the particles having least amount of thermal energy? Select the correct answer below: gas solid liquid All phases of matter contain the same measure of thermal energy.
Correct answer: solid Solids have the most rigidly packed particles (molecules, ions, or atoms) because they have the lowest amount of thermal energy compared to the other states of matter for that substance.
In order to identify a chemical property of matter, one thing scientists might look for is: Select the correct answer below: a change in shape of the substance. a change in state of matter. the formation of a precipitate. the freezing of a substance
Correct answer: the formation of a precipitate. In order to identify a chemical property for a type matter, scientists look for a chemical change, such as the formation of a precipitate during a reaction.
Which of the following describes a chemical property of a substance? Select the correct answer below: the substance emits a gas when dropped in water the substance is dark green the substance is sour to the taste the substance has a pleasant odor
Correct answer: the substance emits a gas when dropped in water If a gas is emitted, this indicates a chemical reaction has occurred, so assessing this reactivity is an example of a chemical property.
