chem hw study
14) if we wish to convert a value in years into days, a conversion factor we could use would be:
days must be on top and years on the bottom so that we can appropriately cancel out the existing unit. 365 days/1 year
water is a?
molecule Water is a molecule because it is made up of 3 atoms that are chemically bonded to each other.
Which of the following is an example of a heterogenous mixture?
salad dressing
An example of homogeneous mixture is: Select the correct answer below: -muddy water -pure water -ice water -saline water
saline water (mix of salt and 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).
2) Which of the following is NOT a SI base unit?
"oz" is the abbreviation for ounce, which is not a SI base unit of measurement. "cd" is for candela, "m" is for meter, and "s" is for second
7) A power plant delivers about 21,000,000,000,000watts of electricity. Write this quantity in terawatts.
"tera" means 1012, so 1TW=1012W. To convert watts to terawatts, move the decimal point to the left 12 times, filling in or removing zeros as needed, and then use a prefix symbol, T, to represent 1012. 21,000,000,000,000W=21×1012W=21TW
Which of the following terms describes the smallest particle of a substance that still retains the chemical properties of that substance? Select all that apply. -a mixture -a molecule -an atom -a neutron
molecule and atom depending on whether the substance in question is an element or a compound, either an atom or a molecule is the smallest particle of that substance that retains its chemical properties. A substance cannot decompose into protons, neutrons and electrons without changing its very nature.
If something is a compound, it is also __________ .
pure substance... Pure substances are either elements or compounds. A compound is a pure substance composed of more than one element. A compound is not a mixture because mixtures can be separated by physical means. Since a compound is composed of more than one type of atom, it cannot be a single atom.
17) what is a conversion factor?
ratios of physical quantities used to compare desired units Conversion units are ratios of physical quantities used to compare between two desired units. They are not experimental or theoretical
Which of the following is NOT a physical property of a bronze coin? Select the correct answer below: -that it is shiny -that it is hard and durable -that it will slowly change color over many years -that it sinks in water
that it will slowly change color over many years... The slow color change is due to chemistry that the material participates in over time, and is therefore not a physical property like the other options.
Which of the following is NOT a likely indicator of a chemical change? Select the correct answer below: -the formation of a precipitate -a color change -the change in shape of a malleable metal -the release of gas without adding heat or lowering the pressure
the change in shape of a malleable metal The bending of a piece of metal, like a paper clip, is not a chemical change. Only when a new substance is formed, evidenced by a new material present or a change in color, can a chemical change be guaranteed.
10) Today, the meter is based on:
the distance light travels in a particular fraction of a second
16) The speed of light is around 6.706×108 miles per hour. What is the speed of light in units of miles per minute?
we must use the fact that 60min=1hr. 6.706×108mihr×1hr60min=1.118×107miminTherefore, we find that the speed of light is approximately 1.118×107 miles per minute.
9) If a scientist wanted to determine the amount of space occupied by an object, she would measure its:
She would measure the object's volume to determine the amount of space it occupies. If she wanted to determine the amount of matter in an object she would measure the mass and if she wanted to determine the size of the object she would measure the length
4) Which of the following statements BEST describes the SI system of units
The SI system is used in the scientific and medical fields and is an expanded form of the metric system
12) The standard SI unit of mass is the kilogram.
The gram and the pound are also units of mass but only the kilogram is the SI unit of mass. The meter is the SI unit of length.
8) 35gigatons equals __________.
The prefix "giga" means 10^9, so it can be written as the following. 35gigaton=35×10^9tons in scientific notation, the decimal part must be between 1 and 10. Move the decimal point in 35 to the left one place, and, since this makes the number smaller by a power of 10, add 1 to the exponent on 10 to compensate. 35×109tons=3.5×10^10tons.
Which of the following are considered pure substances? a.element b.compound c.mixture d.none
element and a compound. An element and a compound are both considered to be pure substances. Elemental iron, for example, contains only iron atoms. Pure water, which is a compound, contains only water molecules, and nothing else.
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.
formation of 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.
A __________ contains more than one type of substance as part of its composition. a.compound b.mixture c.pure substance d. element
a 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.
15) One year consists of 365 days. This is closest to how many seconds?
kilo (103), mega (106), giga (109), and tera 1012. One year is 365 days and each day has 24 hours. 365 days×24 hoursday×60 minuteshours×60 secondsminute=31,536,000 seconds Writing it in scientific notation gives: 31,536,000 seconds=3.1536×107 seconds.
What is the result of two or more atoms forming chemical bonds with each other? Select the correct answer below: -a proton -an element -an atom -a molecule
molecule
Which of the following is an example of a physical property? Select the correct answer below: -boiling point -melting point -color -all of the above
all of the above Boiling point, melting point, and color are all considered physical properties.
Which of the following is a molecule? 1. Water2. Ozone3. Glucose4. All of the above
all, water, ozone, and glucose
3) Which of the following is NOT a unit used in the SI system?
atomic mass unit Ampere, gram. and meter are all units in the SI system. An atomic mass unit is a commonly used measurement in chemistry, but it is not part of the SI system.
Which of the following examples is considered a physical change? Select all that apply. Great work! That's correct. boiling water slicing potatoes into fries freezing juice to make ice pops food rotting on the counter
boiling water slicing potatoes into fries freezing juice to make ice pops
An example of a homogeneous mixture is: Select the correct answer below: -gold -brass -aluminium -copper
brass.... A homogeneous mixture is a substance with uniform composition throughout. Brass is a mixture of copper and zinc. All other options are pure substances (elements).
Select a statement that best completes the following sentence: During a __________ process, the identity of the molecule ___________. Select the correct answer below: -chemical; does not change -chemical ; changes -physical; changes -None of the above
chemical ; changes During a chemical process, the identify of the molecule changes. A chemical change always produces one or more types of matter that differ from the matter present before the change.
A compound is a chemical substance composed of two or more kinds of elements in a fixed ratio. By what means can the components of a compound be separated?
chemical means... A compound cannot be separated into its component elements by physical means, but it can be separated into elements by chemical means.
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
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 NOT a physical property? Select the correct answer below: -combustibility -conductivity -malleability -elasticity
combustibility.. the rest are physical properties Combustibility is the measure of how readily something will burn in the presence of oxygen, which is a chemical reaction. Therefore combustibility is a chemical property.
1) How many meters (m) are there in 7 centimeters?
7x1m/100cm= .07... 1 centimeter is 1100 of a meter because the prefix, centi, means 100. A centimeter is smaller than a meter. Therefore, 7 centimeters would be 7100 or 0.07 of a meter.
What can be observed without changing the composition of matter? Select the correct answer below: -flammability -reactivity -boiling point -toxicity
Physical properties include: appearance, texture, color, odor, melting point, boiling point, density, solubility, polarity, and many others.
Which of the following statements about atoms and molecules are true? Select all that apply: -All substances are composed of molecules. -Atoms in a molecule are held together by chemical bonds. -All molecules are composed of atoms. -All substances are held together by chemical bonds.
-All molecules are composed of atoms. -Atoms in a molecule are held together by chemical bonds.
13) Express 100 kmhr in meters per second. Report your answer with three significant figures.
100 km1 hour×1 hour60 minutes×1 minute60 seconds×1000 meter1 km=27.8 m/s All units except meters and seconds cancel out and we get 27.8 m/s
Which of the following can be broken down into elements by chemical means?
COMPOUND>> 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.
5) The international metric system used in science, medicine, and industry is known as:
International system of units
6) The mole is an SI unit used to measure amount of a substance.
It's similar to how a 'dozen' is an amount that means 12 of something. Moles measures amount of a substance
11) Length is a measurement of distance
Mass is the amount of matter in an object, pressure is the force per unit area, and volume is the space occupied by any sample of matter
Which of the following is NOT a substance made of one type of molecule. Select the correct answer below: -carbon dioxide -glucose -water -a cell within the human body
a cell within the human body.... A cell is a collection of many different types of molecules.
A large change in temperature (not resulting from external heating) with the appearance of gas bubbles is most likely an indication of: -a chemical change -only physical changes occurring -molecules are undergoing physical changes
a chemical change
