A student mixes 20.0gof white KCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred?
a- The solution does not change color after stirring.
b- The KCl crystals are no longer visible after mixing with water.
c- There is a temperature change in the solution during the dissolving process.
d- After the water has evaporated, the white crystals in the beaker have a mass of 20.0g
Answer:d
Explanation: over time water evaporates which leaves you with the white crystals mass
A student in a beaker mixes 20.0 g of white KCl crystals with distilled water; no crystals are visible, and the solution is clear, indicating that the physical change has occurred, which is that after the water has evaporated, the white crystals in the beaker have a mass of 20.0 g; that is option d.
What is the significance of the physical change?The physical change includes the change in the shape and size of the substances but not the chemical change, as in the case of here the crystal, which is left behind after the evaporation of the solution without any change in the chemical composition.
Hence, a student in a beaker mixes 20.0 g of white KCl crystals with distilled water; no crystals are visible, and the solution is clear, indicating that the physical change has occurred, which is that after the water has evaporated, the white crystals in the beaker have a mass of 20.0 g; that is option d.
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Pls help I will give u points pls
Answer:
i think D
Explanation:
The most recent model of an atom is the_____.
Points: 67
Answer:
answer is electron cloud model
calculate the energy of a photn of red light with a wavelength of 6.45x10^-5cm
Answer:
6.45 × 10-5 centimeters
Explanation:
Compare the structure and bonding of the three compounds:
• carbon dioxide
•magnugum ondo
•silicon dioxide
(6 mark question)
Silicon dioxide is a covalent network solid. Magnesium oxide is an ionic compound while carbon dioxide is a covalent molecule.
Carbon dioxide is a covalent compound. The compound contains polar C-O bonds but overall the compound is nonpolar as such the molecules are held together by only weak dispersion forces.
The compound magnesium oxide is an ionic solid. It is composed of magnesium ions and oxygen ions in a crystal lattice. Owing to the fact that the ions are very small, the lattice energy is large and the compound is almost insoluble in water.
Silicon dioxide is a covalent network solid which is composed of chains of silicon - oxygen bonds. The network solid forms a very rigid structure having a high melting point.
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Match each term in the first column with an example in the second column. On a sheet of paper, write the letter of the answer.
1. physical property
2. chemical property
A ability to burn
3. solid
4. liquid
B rust appears on a nail C a puddle freezes
5. physical change
6. chemical change
D substance that has a definite shape and volume
E temperature or density
F substance that has a definite volume, but no definite shape
Answer:
wait can you go more in detail i can help you because i dont understand whats going on
What type of chemical reaction is Al + FeO --> Al2O3 + Fe
Answer:
single reaction equation
Explanation:
Type of Chemical Reaction: For this reaction we have a single replacement reaction. Balancing Strategies: In this single replacement (also called displacement) reaction the Al and Fe are switching places.
When drawing an atom, we draw the same number of electrons as
protons
Select one:
True
False
Answer:
true
I hope it helps.
I am having the worst day ever, Someone please cheer me up. :( I'll mark you as brainiest. :(
Once I told a chemistry joke
I got no reaction.
What do you do with a sick chemistry teacher?
If you can't helium, and can't curium, you might as well barium.
I don't trust atoms,
I heard they make up everything
Hope I helped make ur day. :)
Someone please help with number 9.
Answer:
Its development and progression are usually linked to a series of changes in the activity of cell cycle regulators. For example, inhibitors of the cell cycle keep cells from dividing when conditions aren't right, so too little activity of these inhibitors can promote cancer.
Superficially, the connection between the cell cycle and cancer is obvious: cell cycle machinery controls cell proliferation, and cancer is a disease of inappropriate cell proliferation. Fundamentally, all cancers permit the existence of too many cells.
Explanation:
hope it helps
which is the first news paper of Nepal
Answer:
Nepal Bhasa Patrika
Explanation:
Nepal Bhasa Patrika
one difference between a chemical formula and a chemical equation is that the chemical equation shows:
Chlorine has 7 valence electrons. Describe the type of bond that sodium would have
with chlorine. Write the chemical formula of the compound these two elements would form together. (i figured it out nvm)
1: How can you divide Pepper & Sand to make a solution?
Answer:
Mixture of sand, pepper powder and salt can be separated by dissolving the mixture into water. Sand and pepper powder is insoluble in water while salt is soluble. So they are separated by the filtration method.
How can I increase the time over which the collision occurs?
Explanation:
The laws of physics determine that the force of impact increases with the square of the increase in speed. So, if you double the speed of a car, you increase its force of impact four times. If you triple the speed, the impact is nine times as great.Observe that the greater the time over which the collision occurs, the smaller the force acting upon the object. Thus, to minimize the effect of the force on an object involved in a collision, the time must be increased.
discuss why people use the scientific method
Answer:
They use the scientific method to study different aspects of how people think and behave. They also use the scientific method because it is evidence-based, standardized and objective in conducting experiments.
When a hurricane approaches land, people living directly on the
coast should always evacuate when told to do so by authorities.
Answer:
True
Explanation:
When a hurricane is dangerous enough that authorities say to evacuate, you should for your own safety.
Sounds with great amplitude are ____________
Answer: LOUDER
Explanation:
. A larger amplitude means a louder sound, and a smaller amplitude means a softer sound.
WILL GIVE BRAINLIEST
Which model provides more information-a chemical formula or a sketch of the molecule
like in the structural formula? Explain your reasoning.
Answer:
Explanation
:Both b/c a chemical formula tells you how many and a sketch formula shows how they are bonded together.
Molecular formulas show how many atoms of each element one molecule of a compound contains. Note: Ionic compounds are generally crystalline solids with high melting points. Other compounds, however, have very different properties.
Can someone give me an example of a Hypothesis?
Answer:
if I eat more vegetables,then I will lose weight faster.
Between what two elements does hydrogen bonding occur?
Answer:
it can occur between hydrogen and 3 other elements
Explanation:
These elements are:
Nitrogen
Oxygen
Flourine
A reaction that had two compounds as reactants and two compounds as products is most likely a
double-replacement reaction
Can someone help please
Answer:
To achieve stability
Explanation:
Chemical reactions happen so that the atoms of the elements involved in the chemical reaction will become stable and therefore achieve stability.
1. 4Na + 02 → 2Na20
find the reaction
oxidation reaction
Explanation:
2 Na2O → 4 Na + O2
This is an oxidation-reduction (redox) reaction:
4 NaI + 4 e- → 4 Na0(reduction)
2 O-II - 4 e- → 2 O0(oxidation)
Na2O is an oxidizing agent, Na2O is a reducing agent.
The bacteria are known to be prokaryotes. Prokaryote means
A
organisms whose cells have no nucleus
B
organisms who are made of many cells
C
organisms who make their own food
D
organisms whose cells have a nucleus
Answer:
prokaryote, also spelled procaryote, any organism that lacks a distinct nucleus and other organelles due to the absence of internal membranes. ... Bacteria are among the best-known prokaryotic organisms. The lack of internal membranes in prokaryotes distinguishes them from eukaryotes.
Explanation:
has anyone done 4.3.4 Practice: Mixtures of Matter...I need help :/
The types of mixtures are homogeneous and heterogeneous, you can identify these based on their features.
A mixture occurs when two or more materials are mixed or combined. For example, if you combine two or more liquids. Moreover, this can lead to two types of mixtures:
Homogenous mixtures.Heterogeneous mixture.Each of these has defined features that affect the characteristics and properties of a mixture:
Homogenous mixtures:
Once the mixture is done its components cannot be easily identified.The composition is uniform.Some examples include lemonade, smoothy, and concrete.Heterogeneous mixture:
The components can be easily identified and even separated after the mixture.The composition is not uniform.Some examples include salad, pizza and oil mixed with water.Note: This question is incomplete because of this, I answered based on general knowledge.
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Which of the following is unlikely to form a compound?
a. S
b. H
c. K
d. Ar
d. Si
Answer:
I think the answer is Ar, k or just k. Can you pick two answers?
Explanation:
I hope this helps.
P.S. you put two d's
Which statement correctly describes the relationship between molecular structure, the strength of electrostatic forces between
molecules, and the boiling point of a substance? (1 point)
The boiling point of a substance affects the strength of electrostatic forces, which can affect the molecular
structure
The boiling point of a substance affects its molecular structure, which can affect the the strength of
electrostatic forces.
Molecular structure affects the strength of electrostatic forces, which can affect the boiling point of a
substance
Stronger electrostatic forces cause a stronger molecular structure and lower boiling points
Molecular structure affects the strength of electrostatic forces, which can affect the boiling point of a substance is the statement that correctly describes the relationship between these terms.
The molecular structure is the way in which the atoms that are in a molecule are arranged in space, this is defined by a series of forces that hold the atoms together in a specific arrangement.
The boiling point is the temperature at which the vapor pressure of the liquid equals the pressure that surrounds the liquid, when this happens, the liquid transforms into gas.
For a compound to vaporize, the forces that hold the molecules together must be broken, this means that the boiling point of a compound depends on the attraction between the molecules, that is, on the forces that determine the molecular structure.If the molecules are held together by strong electrostatic forces, it will take a lot of energy to push the molecules away from each other and the compound will have a very high boiling point.Therefore, we can conclude that the boiling point depends on the molecular mass of the substance and the type of electrostatic forces present, that is, the bonds that the atoms establish with each other to form the molecule (molecular structure).
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The modern-day quantum model of the atom is better than John Dalton’s model because it
A. has set electron orbits.
B. has positive and negative particles in the nucleus.
C. can be represented in one dimension.
D. answers many questions about atoms.
Answer:
its D. answers many questions about atoms.
The modern-day quantum model of the atom is better than John Dalton’s model because it " answers many questions about atoms."
What is quantum model ?This concept also referred to as the quantum mechanical and wave mechanical model, would be the cornerstone of contemporary atomic theory. The fact that an electron inside an atom may only exist in a limited range of states or energy is analogous to a standing wave.
What is John Dalton’s model ?Dalton proposed that the concept of atoms will be used to explain the laws of conservation of mass as well as definite proportions. Imagining atoms as "solid, massy, hard, impenetrable, moving objects," he claimed that almost all matter would be composed of these tiny, indivisible particles.
Dalton also stated that almost no atom might be formed, converted into another, as well as destroyed. The complex shapes of orbitals also known as electron clouds used in the quantum mechanical atomic model are areas of space where an electron is likely to be present. So rather than being based on certainty, this model would be probability based.
Therefore, the correct answer will be option (D)
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Balance the equation:
Ca(OH)2 +2 HBr → CaBr2 + 2 H2O