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Changes
Mixtures
Phases of Matter
Lab
Density
100
Explain the difference between a chemical and physical change.
There are several differences between a physical and chemical change in matter or substances. A physical change in a substance doesn't change what the substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed
100
Two or more ____________ or __________ not chemically combined is a mixture.
Atoms or molecules
100
What happens to kinetic energy during a phase change and why?
It stays constant because particle movement DOES NOT change. Temperature does not increase or decrease.
100
During the drug test lab, what are two physical properties we studied?
Conductivity, particle appearance, solubility in water, pH
100
Define density
Amount of matter in a given space
200
Explain the law of conservation of mass and how does it relate to chemical changes?
the principle that in any closed system subjected to no external forces, the mass is constant irrespective of its changes in form; the principle that matter cannot be created or destroyed. Expand. Also called law of conservation of mass, conservation of matter.
200
True or false. Mixtures can be separated chemically.
False. Can only be separated physically.
200
Describe the particle arrangement, movement, and spacing for the phase: liquid.
Liquids have definite volume, but indefinite shape. They are free to form droplets and puddles when they are not inside a container. When a liquid is inside a container, it will take its shape. Unlike gases, a liquid will not change its volume to spread out and completely fill a container.
200
Explain how to calculate an Rf value for a paper chromatography lab
Distance dye travels/distance solvent travels= decimal
200
If you know the dimensions of an object are 5cm, 9cm, and 3cm. Explain how to calculate its volume and give units.
L x W xH= 5*9*3= 135cm3 cm x cm x cm=cm3
300
What is the difference between an intensive vs extensive property?
An intensive property is a bulk property, meaning that it is a physical property of a system that does not depend on the system size or the amount of material in the system. ... Mass and volume are extensive properties, but hardness is intensive.
300
Name two mixture separation techniques and explain how/when to use them.
Paper chromatography- homogeneous mixtures Distillation is a process that can be used to separate a pure liquid from a mixture of liquids. It works when the liquids have different boiling points. Distillation is commonly used to separate ethanol - the alcohol in alcoholic drinks - from water. The mixture is heated in a flask. Filtration is a method for separating an insoluble solid from a liquid. When a mixture of sand and water is filtered: the sand stays behind in the filter paper (it becomes the residue) the water passes through the filter paper (it becomes the filtrate)
300
Do you remove or add enthalpy (heat energy) to make a gas go to a liquid?
Remove.
300
Which gas was produced during the law of conservation of mass lab?
Carbon dioxide
300
How would you calculate the mass of an object with a density of 9.4g/cm3 and a volume of 146cm3?
146 cm3 x 9.4 g/cm3 V x D= M 1372 grams
400
What was the chemical equation from the law of conservation of mass lab? What was the precipitate?
Acetic acid present in vinegar will readily react with baking soda (sodium bicarbonate) to form sodium acetate with the effervescence of carbon dioxide. The equation for the reaction is: CH3COOH + NaHCO3 = CH3COONa + CO2 + H2O. Precipitate = sodium acetate= CH3COONa
400
What is the history of paper chromatography and how is it used in chemistry?
The first chromatograph was invented by Russian botanist Mikhail Semenovich Tsvett (1872-1919). While working in Poland, Tsvett was looking for a method of separating a mixture of plant pigments (tints) which are chemically very similar to each other. To isolate different types of chlorophyll, he trickled a mixture of dissolved pigments through a glass tube packed with calcium carbonate powder. As the solution washed downward, each pigment stuck to the powder with a different degree of strength, creating a series of colored bands. Each band of color represented a different substance. Tsvett referred to the colored bands as a chromatogram. He also suggested that the technique (now called adsorption chromatography) could be used to separate colorless substances. Read more: http://www.discoveriesinmedicine.com/Bar-Cod/Chromatography.html#ixzz4uMR5AbGK Chromatography works by separating the individual parts of a mixture so that each one can be analyzed and identified. In the decades since its invention, the chromatograph has become an essential piece of equipment in bio-chemical laboratories. Using the analytical technique of chromatography, scientists can tell what chemical compounds are present in complex mixtures. These mixtures include such diverse things as smog, cigarette smoke, petroleum products, or even coffee aroma. Without chromatography, chemists might not have been able to synthesize proteins such as insulin or understand how plants use the sun's energy to make food. Read more: http://www.discoveriesinmedicine.com/Bar-Cod/Chromatography.html#ixzz4uMR7mIZN
400
How is ethalpy different than kinetic energy?
Enthalpy /ˈɛnθəlpi/ ( listen) is a measurement of energy in a thermodynamic system. Aka heat. It can only be used to do ONE THING at a time: either change the speed of molecules (kinetic energy) OR change how close together or far apart molecules are (particle arrangement).
400
During the freezing/melting point of water lab, why did we add salt to the larger beaker of ice?
To lower the freezing point of water by interrupting water's ability to form hydrogen bonds with other water molecules.
400
Two substances have the same volume but different masses. Element 1 sinks in water and the other, Element 2, floats. Which one has the SMALLER volume and why?
Element 1 has the smaller volume because 10/9 = 1.111 which sinks in water, while Element 2 has the larger volume because 10/11 is 0.9 which floats in water. Put in the same masses, ex. 10, and then you change the volume numbers to make the density of Element 1 less than 1 (i.e. floats) and the density of Element 2 greater than 1 (i.e. sinks)
500
Which is a chemical change and WHY? Using hot water to expand a metal lid Freezing of water Leaves changing color in the fall
Leaves changing color in the fall Chemical reaction going on- chlorophyll pigment being destroyed
500
Which intensive physical property can be used to separate mixtures using filtration?
Particle size
500
Draw a phase change diagram for water and label the phase changes and set phases: solid, liquid, gas.
https://d2gne97vdumgn3.cloudfront.net/api/file/LjCJHTzRZG8kxGU8Kvx8
500
Define a precipitate and give an example from lab.
Sodium Acetate. In chemistry, a precipitate is an insoluble solid that emerges from a liquid solution. The emergence of the insoluble solid from solution is called precipitation. Often the precipitate emerges as a suspension. Precipitates can form when two soluble salts react in solution to form one or more insoluble products. soluble salt 1 + soluble salt 2 → insoluble salt (precipitate) applejuice Apple juice is improved by removal of undesirable substances as a precipitate. Let's hope there's no strychnine in it! Precipitates can also form when the temperature of a solution is lowered. Lower temperatures reduce the solubility of salts, which may result in their precipitation as solids.
500
Why is density a physical intensive property? What is the density of liquid water vs solid water and why? Explain the pattern?
It is a physical intensive property of matter because it is constant for all samples of the SAME element regardless of the amount of matter in the sample. Water has a slightly smaller density as a solid: 0.934 g/cm3, so it floats in liquid water, which has a density of 1.0g/cm3. This is special because usually substances have smaller densities when they heat up, thermal expansion, as the VOLUME increases which makes the DENSITY decrease as it is an inverse relationship (one goes up, the other goes down)