Chemical Changes
Chemical changes take place at the molecular level. A chemical change produces a new substance. Another way to think of it is that a chemical change accompanies a chemical reaction. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.
Physical Changes
Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance, although the starting and ending materials may look very different from each other. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.
How to Tell Chemical & Physical Changes Apart
A chemical change makes a substance that wasn't there before. There may be clues that a chemical reaction took places, such as light, heat, color change, gas production, odor, or sound. The starting and ending materials of a physical change are the same, even though they may look different.
hope this helps
5 star and brainliest?
A student prepared several aqueous sodium chloride (NaCl) solutions to observe boiling point elevation at various molal concentrations, however, several errors were made throughout the procedure. Determine whether these errors would cause the observed boiling point to be increased or decreased relative to the expected boiling point, based on the procedure, or have no effect on the experimental results.
The question is incomplete, the complete question is;
A student prepared several aqueous sodium chloride (NaCl) solutions to observe boiling point elevation at various molal concentrations, however, several errors were made throughout the procedure. Determine whether these errors would cause the observed boiling point to be increased or decreased relative to the expected boiling point, based on the procedure, or have no effect on the experimental results.
* The flask is washed with water but not thoroughly dried before preparing the solution
* The mass of NaCl used to prepare the solution is 5.400 grams instead of 4.400 grams
* Some of the prepared solution splashes out of the flask prior to observation of the boiling point
* When making the salt solution, 55.0 milliliters of water is added instead of 50.0 milliliters
Answer:
The flask is washed with water but not thoroughly dried before preparing the solution - decrease
The mass of NaCl used to prepare the solution is 5.400 grams instead of 4.400 grams
-increase
Some of the prepared solution splashes out of the flask prior to observation of the boiling point- have no effect
When making the salt solution, 55.0 milliliters of water is added instead of 50.0 milliliters- decrease
Explanation:
If the flask is washed but not dried, then the solution will be further diluted than expected. As a result of this further dilution, the observed boiling point will be less than the expected boiling point because the boiling point depends on the solution's concentration.
If more solute is added than expected, the concentration of the solution is increased and the boiling point also increases above the expected boiling point due to the increase in amount of solute present.
If some of the solution splashes out of the flask prior to boiling, the boiling point is not affected because the concentration of the solution was not altered. The boiling point only changes when the concentration of the solution is changed.
If 55 ml of water is added instead of 50 ml, the solution is now more dilute than expected thereby reducing the concentration of the solution and the boiling point. Remember that, as the concentration of the solution decreases, the boiling point decreases accordingly.
3. The picture below is an example of a _________ _________. (Answer is 2 words)
Answer:
I can't see any picture?????
What is wrong with the chemical reaction written below?
REACTANT(S)
PRODUCTS
Magnesium + Chlorine ------>
Magnesium Chloride
12 g Magnesium
+
8 g Chlorine
25 g Magnesium Chloride
a) Magnesium will never react with chlorine
b) The mass of your total product is greater than your total reactants
c) The name of the product is incorrect
d) Nothing is wrong with the above reaction-it is perfectly correct as written!
Answer:
b) The mass of your total product is greater than your total reactants
Explanation:
Mass of reactants is 20 and product is 25 which never occurrs in real
Clear liquid is on top of the green liquid,green liquid is on top of the red liquid.What is the order of density of the liquids, from highest to lowest
Answer:
This indicates there will be the densest (heaviest) liquid on the bottom of the jar there will be the least dense (lightest) liquid on top. Syrup, glycerin, water, oil, and then alcohol would be on top of the order of liquids from hardest to lightest.
Based on the following chemical equation how many hydrogen atoms are present in the products side?
N2 + 3H2 ----> 2NH3
Question 2 options:
5
3
6
1
The number of Hydrogen atoms = 6 atoms
Further explanationGiven
Reaction
N₂ + 3H₂ ⇒ 2NH₃
Required
The number of Hydrogen atoms
Solution
The reaction coefficient of a chemical equation shows the mole ratio of the reacting compound.
On a compound the reaction coefficient indicates the number of molecules
Whereas the subscript after the atom shows the number of atoms in that compound
Product from the reaction : 2NH₃
Number of H-atoms :
= 2 x 3
= 6 atoms
Help answer this if you know it thank you!
Answer:
evolution
Explanation:
Answer:
because bird species are reproduced sexually
so there would be some variations in every generation.
that's why birds could be different from their ancestors.
Consider this reaction: At a certain temperature it obeys this rate law. rate Suppose a vessel contains at a concentration of . Calculate how long it takes for the concentration of to decrease by . You may assume no other reaction is important. Round your answer to significant digits.
This question is incomplete, the complete question is;
Consider this reaction:
2H₃PO₄(aq) → p₂o₅(aq) + 3H₂O(aq)
At a certain temperature it obeys this rate law.
rate = ( 46.65 M⁻¹.s⁻¹) [ H₃PO₄ ]²
Suppose a vessel contains H₃PO₄ at a concentration of 0.660 M .
Calculate how long it takes for the concentration of H₃PO₄ to decrease to 20.0% of its initial value .
You may assume no other reaction is important.
Round your answer to significant digits.
Answer:
time taken is 8.574 × 10⁻⁴ s
Explanation:
Given that;
rate = k[ H₃PO₄ ]²
rate constant k = 46.65 M⁻¹.s⁻¹)
Initial concentration A₀ = 0.660 M { which will be 100%}
final concentration At = 20%
for the concentration of H₃PO₄ to decrease to 20.0% of its initial value = ?
we know that;
rate constant k = 1/t [ 1/At - 1/A₀ ]
we substitute
46.65 = 1/t [ 1/20 - 1/100 ]
46.65 = 1/t [ 0.04 ]
46.65 = 0.04/t
46.65t = 0.04
t = 0.04 / 46.65
t = 0.0008574 ≈ 8.574 × 10⁻⁴ s
Therefore, time taken is 8.574 × 10⁻⁴ s
Molecules move faster and farther apart when state changes from ? to ?
The molecules move faster and farther apart when the state changes from the liquid state to the gaseous state.
What are states of matter?The matter exists in different forms in nature. Some substances have a fixed shape like wood and stone and can flow, take the shape of their container such as water, while there are forms of matter that do not have certain shapes or sizes.
In solids, the molecules are closely packed and thus solids have a rigid structure. The compact packing of solids means that the molecules are very close to each other and the molecules do not show movement. The kinetic energy of molecules in the solid is the least.
In liquids, the molecules are some distance away from each other and they show movements. Since the molecules in liquid show significant movement, they have some kinetic energy. The kinetic energy of molecules in the liquid is greater than that of solids.
In gases, the molecules are farther from each other and thus their molecules show large amounts of movement. The kinetic energy in gases is the greatest in comparison to solids and liquids.
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The 10x SDS gel electrophoresis buffer contains 250mM Tris HCl, 1.92M Glycine, and 1% (w/v) SDS. Buffers are always used at 1x concentration in the lab (unless specified otherwise in the protocol), so you will have to dilute the 10x buffer to 1x before use. What is the concentration of Tris and SDS in the 1x buffer
Answer:
25 mM Tris HCl and 0.1% w/v SDS
Explanation:
A 10X solution is ten times more concentrated than a 1X solution. The stock solution is generally more concentrated (10X) and for its use, a dilution is required. Thus, to prepare a buffer 1X from a 10X buffer, you have to perform a dilution in a factor of 10 (1 volume of 10X solution is taken and mixed with 9 volumes of water). In consequence, all the concentrations of the components are diluted 10 times. To calculate the final concentration of each component in the 1X solution, we simply divide the concentration into 10:
(250 mM Tris HCl)/10 = 25 mM Tris HCl
(1.92 M glycine)/10 = 0.192 M glycine
(1% w/v SDS)/10 = 0.1% w/v SDS
Therefore the final concentrations of Tris and SDS are 25 mM and 0.1% w/v, respectively.
. The level of mercury in a stream was suspected to be above the minimum considered safe (1 part per billion by weight). And analysis indicated that the concentration was 0.68 parts per billion. Assume a density of 1.0 g/mL and calculate the molarity of mercury in the stream.
Answer:
3.39x10⁻⁹ M
Explanation:
Let's assume we have 1 mL of the stream. With a density of 1.0 g/mL, we would have 1 g of the stream.
Now we calculate the mass of mercury present in 1 g of the stream, using its given concentration (0.68 ppb):
ppb = ng Mercury / g stream0.68 ppb = ng Hg / 1 gMass of mercury = 0.68 ngNow we convert that mass into moles, using mercury's atomic mass:
0.68 ng = 0.68 x 10⁻⁹ g0.68 x 10⁻⁹ g ÷ 200.59 g/mol = 3.39x10⁻¹² molFinally we calculate the molarity of mercury, as we know that there are 3.39x10⁻¹² Hg moles in 1 mL of the stream:
1 mL = 0.001 LMolarity = 3.39x10⁻¹² mol / 0.001 L = 3.39x10⁻⁹ M
Which statement correctly describes ionic bonds? Multiple Choice An ionic bond only forms between two atoms of the same element. Ionic bonds usually form between electrically neutral, stable atoms. An ionic bond is the electrostatic force that holds ions together when they form bonds. All of the answer choices are correct.
Answer:
An ionic bond is the electrostatic force that holds ions together when they form bonds
Explanation:
An ionic bond is formed when a metal looses electron(s) to a non metal leading to the formation of a positive ion and a negative ion.
An ionic compound is actually an ion pair, the ions are held together by strong electrostatic forces.
This strong electrostatic force that holds the ion pair together in ionic compounds is what we commonly call the IONIC BOND.
Answer:
An ionic bond is the electrostatic force that holds ions together when they form bonds
Explanation:
I took this test and it was the correct answer :)
In the Energy and Specific Heat lab, what temperature should be recorded as the final temperature of the water when measuring the food sample?
A. The temperature of the water when the food sample is first lit
B. The temperature of the water when the food sample has finished burning completely.
C. The highest temperature the water reaches as the sample burns
D. The temperature of the water after the food sample ash has been removed
Answer:
B. The temperature of the water when the food sample has finished burning completely.
Explanation:
Heat or thermal energy is a form of energy that transfers from one object to another due to a temperature difference between the objects. The units for heat are joules or calories.
Calorimetry is the measurement of heat energy released or absorbed in a chemical reaction. A calorimeter is used in calorimetry. The calorimeter operates on the Law of Conservation of Energy which states that energy is never created or destroyed but is transformed from one form to another or between objects.
In food calorimetry, the energy released when food is burned is measured by recording the rise in temperature of water in a calorimeter when a given mass of a food sample is burned completely.
Energy can be calculated using the formula: Q = mc ∆T
where Q = the energy in joules or calories, m = the mass in grams, c = specific heat and ∆T = the change in temperature (final temperature - initial temperature).
The temperature of the water when the food sample has finished burning completely is taken as the final temperature of the water. The sample is allowed to smolder for sometime before recording the final water temperature. This is because the water temperature will continue to rise after the flame has gone out.
As the food burned,
energy was
nergy. Thus, a
thermal
transformed intos
chemical
form of Select
nuclear
$ converted to a
form of
Select
energy.
Check
Answer:
I don't get it is it even a question?
Which of the following is the poorest conductor of electricity?
Calcium (Ca)
Silicon (Si)
Fluorine (F)
Sodium (Na)
Cobalt (Co)
Answer:
Fluorine (F)
Explanation:
The poorest conductor of electricity from the given choices is fluorine. This is because fluorine is a non - metal.
Like other non - metals, fluorine does not conduct electricity.
Only metals are known to conduct electricity and heat readily.
Semi - metals like silicon will conduct electricity under specific condition.
The free mobile electrons in metals makes it easy for them propagate electricity
If it takes 38.70cm of 1.90M NaOH to neutralize 10.30cm of H2SO4 in a battery, what is the molarity of H2SO4?
Answer:
The molarity of the acid, H₂SO₄ is 3.57 M
Explanation:
We'll begin by writing the balanced equation for the reaction. This is illustrated below:
H₂SO₄ + 2NaOH —> Na₂SO₄ + 2H₂O
From the balanced equation above,
Mole ratio of the acid, H₂SO₄ (nₐ) = 1
Mole ratio of the base, NaOH (n₆) = 2
Finally, we shall determine the molarity of the acid, H₂SO₄. This can be obtained as follow:
Volume of base, NaOH (V₆) = 38.70 cm³
Molarity of base, NaOH (M₆) = 1.90M
Volume of acid, H₂SO₄ (Vₐ) = 10.30 cm³
Molarity of acid, H₂SO₄ (Mₐ) =?
MₐVₐ / M₆V₆ = nₐ/n₆
Mₐ × 10.3 / 1.9 × 38.70 = 1/2
Mₐ × 10.3 / 73.53 = 1/2
Cross multiply
Mₐ × 10.3 × 2 = 73.53 × 1
Mₐ × 20.6 = 73.53
Divide both side by 20.6
Mₐ = 73.53 / 20.6
Mₐ = 3.57 M
Thus, the molarity of the acid, H₂SO₄ is 3.57 M
Identify the missing species in each nuclear equation. Replace the question marks with the appropriate integer or symbol. Be410⟶B510+Be410⟶B510+ β−10β−10 Si1434⟶P1534+Si1434⟶P1534+ Pt78192⟶Pt78192⟶ pp?+ 42????+ 24α pp?⟶Al1328+β−10
Answer:
1. ¹⁰₄Be ---> ¹⁰₅B + ⁰₋₁β
2. ³⁴₁₄Be ---> ³⁴₁₅P + ⁰₋₁β
3. ¹⁹²₇₈Pt -----> ¹⁹⁰₇₆Os + ⁴₂α
4. ²⁸₁₂Mg ---> ²⁸₁₃Al + ⁰₋₁β
Explanation:
1. In the first equation, Beryllium-10 isotope undergoes beta-decay, emitting a beta-particle to form boron-10 isotope. The balanced nuclear equation is given below:
¹⁰₄Be ---> ¹⁰₅B + ⁰₋₁β
2. In this reaction, silicon-34 isotope undergoes beta-decay, emitting a beta-particle to form phosphorus-34 isotope. The balanced nuclear equation is given below:
³⁴₁₄Be ---> ³⁴₁₅P + ⁰₋₁β
3. In this equation, platinum-192 isotope undergoes alpha-particle decay emitting an alpha-particle to form osmium-190 isotope. The balanced nuclear equation is given below:
¹⁹²₇₈Pt -----> ¹⁹⁰₇₆Os + ⁴₂α
4. In this equation, magnesium-28 isotope undergoes beta-decay, emitting a beta-particle to form aluminum-28 isotope. The balanced nuclear equation is given below:
²⁸₁₂Mg ---> ²⁸₁₃Al + ⁰₋₁β
_H2+_Cl2->_HCl fill in the blanks if necessary.
Answer:
H₂ + Cl₂ → 2HCl
Explanation:
The given reaction expression is shown below:
H₂ + Cl₂ → HCl
We are to balance this given reaction expression.
Let us do this mathematically;
aH₂ + bCl₂ → cHCl
Conserving H : 2a = c
Cl: 2b = c
Now, let a = 1, c = 2 , b = 1
So:
H₂ + Cl₂ → 2HCl
Drag the tiles to the correct boxes to complete the pairs.
Match the descriptions with the types of blas.
selection bias
expectation bias
confirmation bias
contextual bias
paying more attention to evidence that
confirms one's hypothesis and ignoring
evidence that may discount it
to be swayed from one's conclusion by
additional information
coming to a conclusion before all the
evidence has been processed and therefore
unconsciously disregarding evidence to the
contrary
Answer:
Explanation:
here's the answer hope it helps! :)
What role do wolves play in the tundra?
Answer:
predator
Explanation:
Wolves, arctic foxes, and snowy owls are predators in the tundra.
A clone has _________ chromosomes as its parent.
A. Half the number of
B. The same exact
C. double the number of
D. half of the same
Answer:
B. The same exact
Explanation:
I think B because in order to be a clone of your parent you have to have the exact same DNA and chromosomes.
Hope this helps :D
A clone has the same exact chromosomes as its parent.
CLONING:
Cloning is a genetic procedure in which identical copies of a cell or organism is made. Cloning can be done naturally or artificially, however, it follows the process of mitosis. In cloning, the genetic content of a parent cell is used as a template to replicate another cell or organism. Examples of cloning are biological twins, vegetative reproduction in plants etc. Therefore, a clone has the same exact chromosomes as its parent.Learn more at: https://brainly.com/question/12483409?referrer=searchResults
Calculate the mass of butane needed to produce 99.0 g of carbon dioxide.
Express your answer to three significant figures and include the appropriate units.
Answer:
32.7 g
Explanation:
Step 1: Write the balanced combustion reaction
C₄H₁₀ + 6.5 O₂ ⇒ 4 CO₂ + 5 H₂O
Step 2: Calculate the moles corresponding to 99.0 g of CO₂
The molar mass of CO₂ is 44.01 g/mol.
99.0 g × 1 mol/44.01 g = 2.25 mol
Step 3: Calculate the moles of C₄H₁₀ needed to produce 2.25 moles of CO₂
The molar ratio of C₄H₁₀ to CO₂ is 1:4. The moles of C₄H₁₀ needed are 1/4 × 2.25 mol = 0.563 mol.
Step 4: Calculate the mass corresponding to 0.563 moles of C₄H₁₀
The molar mass of C₄H₁₀ is 58.12 g/mol.
0.563 mol × 58.12 g/mol = 32.7 g
Dolphins have the same arm structure as wolves. What type of evidence for evolution does this represent?
A. DNA
B. vestigial structures
C.homologous structures
D. embryology
What are suspensions
Answer: suspensions are a mixture in which solute particles do not disolve. An example is oil and water, oil and water or even flour and water; oil can’t disolve in water
Answer:
Noun: a mixture in which particles are dispersed throughout the bulk of a fluid.
Adjective: the state of being dispersed in a fluid.
Explanation:
I used a dictionary lol
Sulfurous acid reacts with barium hydroxide.
Answer:
Ba(OH)2 + H2SO3 = BaSO3 + H2O -
Explanation:
I need help with answer 1 and 2 ASAP please!!
Answer:
1. B 2.B
Explanation:
How many moles of Fe2O3 are in 17.2g?
A - 1.23
B - 2.75
C - 0.239
D - 0.108
Answer:
C
Explanation:
0.10 moles of Fe[tex]_2[/tex]O[tex]_3[/tex] are in 17.2g. Therefore, the correct option is option D among all the given options.
What is iron(III) oxide?The inorganic chemical with both the formula Fe[tex]_2[/tex]O[tex]_3[/tex] is iron(III) oxide and ferric oxide. It is one of three major iron oxides, the other 2 including iron(II) oxide (FeO), which would be uncommon, and iron(II,III) oxides (Fe[tex]_2[/tex]O[tex]_3[/tex]), which naturally occurs as the mineral magnetite.
Acids have a high affinity for Fe[tex]_2[/tex]O[tex]_3[/tex] . Iron(III) oxide is commonly referred to as rust, and this name is appropriate to some extent because rust has certain features and has a comparable composition; nevertheless, in chemistry, colouration is classified under Hydrous ferric oxide.
mole = 17.2/ 159.69 =0.10moles
Therefore, the correct option is option D.
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Consider Example 12.10. Suppose the experiment is repeated with 0.032 mol of helium instead with everything else staying the same, what is the amount of heat required now to achieve that process
Answer:
120 extracted from the gas
Explanation:
The amount of heat required now to achieve that process is 60 J of heat added to the gas.
Heat required to achieve the processThe amount of heat required to achieve the process is calculated as follows;
[tex]E = \frac{3}{2} nR\Delta T[/tex]
where;
n is number of moles of the helium gas = 0.032 moleR is ideal gas constant = 8.314 J/mol.KΔT is change in temperature (from example 12.10) = 450 K - 300 K = 150 K[tex]E = \frac{3}{2} \times 0.032 \times 8.314 \times (150)\\\\E = 60 \ J[/tex]
Thus, the amount of heat required now to achieve that process is 60 J of heat added to the gas.
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What volume, in liters, would 88.9 grams of a substance occupy if it’s density is 2.38 g/mL
Answer:
V = 0.03735 mL
Explanation:
Given that,
Mass of a substance, m = 88.9 grams
Density of a substance, d = 2.38 g/mL
We need to find the volume occupied by the object. The density of an object is given by mass per unit volume.
[tex]d=\dfrac{m}{V}\\\\V=\dfrac{m}{d}\\\\V=\dfrac{88.9}{2.38}\\\\V=37.35\ mL\\\\V=0.03735\ L[/tex]
So, the volume of the substance is 0.03735 mL.
ANSWER QUICK !!!
How many grams of hydrogen gas will be produced if you start with 15.0 grams of zinc and an excess amount of HCI?
balanced equation:
Zn + 2HCI = ZnCl2 + H2
Answer:
0.48g
Explanation:
Given parameters:
Mass of zinc = 15g
Unknown:
Mass of hydrogen gas = ?
Solution:
To solve this problem, we need to state the balanced reaction expression first;
Zn + 2HCl → ZnCl₂ + H₂
Find the number of moles of Zn;
Number of moles = [tex]\frac{mass}{molar mass}[/tex] = [tex]\frac{15}{63.4}[/tex] = 0.24mol
From the balanced reaction expression;
1 mole of Zn will produce 1 mole of H₂
0.24mole of Zn will produce 0.24mole of hydrogen gas
Mass of hydrogen gas = number of moles x molar mass
= 0.24 x (2 x 1)
= 0.48g
Can soft drinks be part of a healthy diet?
Answer:
yes, but its better to drink water
Explanation: