Elements, Compounds, Mixtures
Pb is an example of an element, compound or mixture? How do you know?
Element because there is only 1 capital letter
A ______ _______ is a characteristic of how a substance behaves during a chemical reaction
chemical property
What states of matter does a filter separate?
solid and liquid
What does it mean if you have 100% yield?
You collected all of the possible material you could have while in lab
This phase change occurs when a solid changes to a liquid
Melting
What is/are pure substance(s)? Examples?
Elements or Compounds; C or O are examples of elements; H2O and NaCl are examples of compounds.
Pure substances have a fixed composition compared to mixtures, which can vary.
Melting point is an example of a ________ _________
physical property
Blueberry pancakes are an example of what type of mixture?
Heterogeneous; solid with solid
What is the unit for percent yield?
%
This phase change occurs when a gas changes to a liquid
condensation
Give an example of a mixture
Air, chocolate chip cookies, sand and water, sugar and salt
During a ________ _________ one substance changes into an entirely new substance
chemical change
What is another name for a homogeneous mixture?
A solution
What does theoretical mean in the equation for percent yield: actual/theoretical x 100%
Theoretical means the maximum amount you SHOULD be able to collect. Calculated or told PRIOR to completing the lab
This phase change occurs when a solid changes directly to a gas without ever going through the liquid phase
sublimation
This type of mixture has a uniform composition and looks the same throughout
homogeneous mixture
Give one example of a physical change to paper
Cut paper, crumple it in a ball, put it through a shredder
What is a way to separate solids from liquids?
Decanting; filtering; evaporation
What is your percent yield if you started with 6 grams of material in a mixture, you separate all the components of the mixture and add them up after separation and recollect 5.4 grams?
90%
Give 2 phase changes that need to RELEASE energy in order to occur
1) Freezing
2) Condensation
3) Deposition
Do substances keep their individual properties or change them in a mixture? Explain using an example.
Substances keep their individual properties in a mixture. For example, when mixing sand and salt, you do NOT see evidence of a chemical reaction. The sand and the salt retain their individual properties. And you are able to separate them and have both substances in their original form.
What are 3 signs a chemical change has taken place?
1) Bubbling/gas produced
2) Odor produced
3) Unexpected color change
4) A solid forms
5) A change in taste
6) Drastic temperature change
7) A change in physical or chemical properties which is not easily reversed
What are 3 separation techniques we used in the lab with sand, salt, stearic acid, and iron?
magnetism, filtration, evaporation, solubility, melting point
If you calculate you can get a maximum of 3 grams of a compound and after lab you get 3.5 grams, what is your percent yield? What could have happened?
116.7%; the material wasn't dry, something else was added of the table, the balance wasn't zeroed to start. You should never get more than 100% yield!
Explain how you know condensation RELEASES energy in order to occur, based on what you know about substances at the molecular level
In condensation, a substance is changed from a gas to a liquid. Gas particles have the highest energy. So in order to go to a liquid, which has less energy, the gas particles need to get rid of, or release, some energy.