Which is the correct order?
a. 3s, 4s, 3p, 3d
b. 4s, 3s, 3p, 3d
c. 3s, 3p, 3d, 4s
d. 3s, 3p, 4s, 3d
Answers
Related Questions
PLZ HELPP Cynthia sees that most of the ice in her iced tea has melted. Assuming the water and the ice are at the same temperature, what happened to the particles in her ice? A.The particles have a much greater amount of kinetic energy than before. B.The particles have the same amount of kinetic energy but no longer vibrate in place. C.The particles have had their kinetic energy converted into thermal energy. D.The particles have a higher temperature than before and are moving more freely.
Answers
Answer:
The most correct option here is D
Explanation:
The difference between a solid (ice) and a liquid (water)/gas (steam) is that the particles in a solid is tightly packed (and do not move) as against the particles in liquid which moves quite freely or those in gases that move very freely.
When a solid (for example ice) is subjected to heat, it's particles receives the heat energy, hence have a higher temperature, and starts moving from its compact position which turns the solid into liquid. This was what happened to the ice in Cynthia's iced tea. The ice got/absorbed an increased temperature from the surrounding tea and it's particles began to move (more freely) thereby causing the ice to melt.
Answer:
D
Explanation:
what does it mean to be in the path of totality science
Answers
Answer:
The track of the Moon's shadow across Earth's surface is called the Path of Totality. This path is typically 16,000 kilometers (about 10,000 miles) long but only 160 kilometers (100 miles) or so wide. In order to see the Sun totally eclipsed by the Moon you must be in the path of totality.
Explanation:
How are reflecting telescopes different from refracting telescopes?
Answers
Reflecting telescopes are preferred for scientific research because they are better suited for gathering large amounts of light and producing high-quality images. However, refracting telescopes are still popular for amateur astronomers and for viewing objects on Earth.
Reflecting telescopes are different from refracting telescopes because reflecting telescopes use mirrors, whereas refracting telescopes use lenses. The reflecting telescope was invented in 1668 by Sir Isaac Newton, and it has since become one of the most popular types of telescopes.
Reflecting telescopes use a mirror to gather and focus light, while refracting telescopes use a lens to do the same thing. Reflecting telescopes can be made much larger than refracting telescopes because it is easier to make large mirrors than it is to make large lenses. The mirror in a reflecting telescope is placed at the back of the telescope, and it gathers and reflects light back to a secondary mirror, which then reflects the light to the eyepiece. The eyepiece is where the observer looks through the telescope.In contrast, the lens in a refracting telescope is placed at the front of the telescope, and it gathers and bends light as it passes through. The lens focuses the light onto an eyepiece at the back of the telescope. Refracting telescopes are generally smaller than reflecting telescopes because of the difficulty of making large lenses.
Another difference between reflecting and refracting telescopes is the way they are constructed. Reflecting telescopes have a simple tube that houses the mirrors and eyepiece, while refracting telescopes have a more complex design with a long tube that contains the lens and eyepiece.
for such more questions on telescopes
https://brainly.com/question/28359353
#SPJ8
The substance oxidized causes the other substance to be reduced and is called the:.
Answers
Answer:
Reducingagent
Explanation:
Hope this helps you :)
Pls mark brainliest :P
`
`
`
Tori
How would you arrange the following amines in order of decreasing base strength?NH3CH3NH2(CH3)2NHNH2Br
Answers
In decreasing sequence of base strength, we have: (CH3)2NH>CH3NH2>NH3>NH2Br amines are present.
The equivalent amine should be considered to be a stronger base. In this case, if the substituted ammonium cation is more stable. In this scenario, the sequence of basicity for aliphatic amines should be as follows: primary > secondary > tertiary. Inductive effect is determined as the reverse of the order.
The acid or base is more potent. The greater the dissociation constant, more potent it is. There is a relation between the strength of an acid as well as base. This is along with the electrolyte it creates. This is because electrolytes are formed as ions are released eventually into the solution. pH scales are used for acids and bases measurement.
Learn more about amines:
brainly.com/question/28522775
#SPJ4
Which of the following correctly describes what happens to the kinetic energy of water when it changes from steam to a
liquid?
There is no change in the kinetic energy of the molecules.
The kinetic energy of the molecules increases.
The kinetic energy of the molecules decreases.
The kinetic energy of the molecules increases then decreases.
Answers
hi <3
i would say the kinetic energy decreases (so option C), as liquid particles are more closely packed than in a gas
hope this helps <3
How many grams of magnesium
sulfate (MgSO4) are dissolved in
0.965 L of a 0.0575 M solution?
Molar Mass Mg: 24.30 g/mol
Molar Mass S: 32.06 g/mol
Molar Mass O: 16.00 g/mol
Answers
Explanation:
Concentration question....
0.965L x (0.0575 mol MgSO4 / 1L) x (120.4g MgSO4 / 1 mol MgSO4) = 6.68g MgSO4
The concept molarity is used here to determine the grams of magnesium sulfate dissolved in 0.965 L of a 0.0575 M solution. The mass of magnesium sulfate in grams is 6.68 g.
What is molarity?The molarity of a solution is defined as the number of moles of the solute present per litre of the solution. It is generally represented by the unit mol/L. The equation used to calculate the molarity is:
Molarity = Number of moles of the solute / Volume of the solution in litres
The molar mass of MgSO₄ = 120.36 g/mol
We have 0.0575 M solution.
That is 0.0575 mol/L × 120.36 g/mol = 6.9207 g/L
Here we want mass in 0.965 L. So the mass is:
Mass = 0.965 L × 6.9207 g/L = 6.68 g
Thus the mass in grams of magnesium sulfate is 6.68 g.
To know more about molarity, visit;
https://brainly.com/question/16727614
#SPJ5
How is energy transferred between the sun and consumers in an ecosystem?
Answers
Answer:
Energy is transferred between organisms in food webs from producers to consumers. The energy is used by organisms to carry out complex tasks. The vast majority of energy that exists in food webs originates from the sun and is converted (transformed) into chemical energy by the process of photosynthesis in plants.☺
write down three use of chlorine
Answers
Answer:
Chlorine is commonly used as an antiseptic and is used to make drinking water safe and to treat swimming pools. Large amounts of chlorine are used in many industrial processes, such as in the production of paper products, plastics, dyes, textiles, medicines, antiseptics, insecticides, solvents and paints.
Explanation:
hope this helped you
please mark as the brainliest (ㆁωㆁ)
Partial bonding, for example, as part of a resonance hybrid, often results in structures with _____.
Answers
Answer:
fractional bond orders
Explanation:
because fractional bond orders
A 10.0 g sample of a gas occupies 7.69 L at 1.00 atm and 27.0 C. The gas has been determined to be diatomic. What is the gas
Answers
ANSWER
EXPLANATION
Given that
The mass of the gas is 10.0g
The volume of the gas is 7.69L
The pressure of the gas is 1.00 atm
The temperature of the gas is 27 degrees Celcius
Follow the steps below to find the molar mass of the gas
Step1; Assume the gas is an ideal gas
\(\text{ Pv = nRT}\)Step 2; Find the number of mole of the gas using the equation above
\(\begin{gathered} \text{ T K = t}\degree C\text{ + 273.15} \\ \text{ T K = 27 + 273.15} \\ \text{ T K = 300.15K} \end{gathered}\)\(\begin{gathered} \text{ R is 0.0825 L.atm . K}^{-1}\text{ mol}^{-1} \\ \text{ 1 }\times\text{ 7.69 = n }\times\text{ 300.15 }\times\text{ 0.08205} \\ \text{ 7.69 = n24.627} \\ \text{ Divide both sides by 24.627} \\ \text{ n = }\frac{7.69}{24.627} \\ \text{ n = 0.312 moles} \end{gathered}\)Step 3; find the molar mass of the sample
\(\begin{gathered} \text{ mole = }\frac{\text{ mass}}{molar\text{ mass}} \\ \text{ cross multiply} \\ \text{ mass = mole x molar mass} \\ \text{ molar mass =}\frac{mass}{\text{ mole}} \\ \\ \text{ molar mass = }\frac{10}{0.312} \\ \text{ molar mass = 32.05} \end{gathered}\)olive oil (density 0.918 g/cm3) separates from the water-vinegar in a salad dressing and is visible as a layer. will the water be the top or the bottom layer? why?
Answers
Olive oil separates from the water-vinegar in a salad dressing and is visible as a layer because the olive oil will be on the top because it has lesser density.
The density of a substance indicates how dense it is in a particular area. Mass per unit volume is the definition of a material's density. In essence, density is a measurement of how closely stuff is packed. It is a special physical characteristic of a certain thing.
On top of the liquid with higher density, the liquid with lower density will float. Compared to water, oil has a lower density. Hence, it floats on top of it. Oil is a non-polar liquid, but water is polar, hence there will be no attraction between their molecules.
Learn more about Density:
https://brainly.com/question/13632227
#SPJ4
is oatmeal a compound
Answers
Answer:
no
Explanation:
its made of a living organisim which in this case is oats
40 POINTS!! AND IF YOU DONT GET IT RIGHT IMMA REPORT YOU AND PLEASE HELP ME
Once upon a time, a mother duckling sat on her eggs with great impatience. How long would it be before they hatched? Finally, one summer day, the mother duckling watched as the eggs cracked, and her cute, yellow ducklings waddled into the world. She was filled with joy until she noticed that one egg, which was larger than all of the others, remained. After many hours, the egg cracked. A large, gray duckling emerged. The mother duck was horrified at the duckling's appearance. The mother duck's only comfort was that the ugly duckling could swim and dive under the water.
As the ugly duckling grew, many animals in the pond criticized him. His feathers were too dark, his neck was too long, and his body was too big. His fellow ducklings refused to recognize that underneath the feathers, the ugly duckling was kind, good, and gentle. The ugly duckling shed many tears because none of the other animals would play with him.
One day, the ugly duckling decided to run far away and find a place where the animals would look past his appearance and be kind and friendly. He came to a pond and sighted three beautiful swans. Their white feathers, long necks, and kind eyes made them look like royalty. The ugly duckling sighed in disappointment. He believed that the swans would never be his friends and looked down into the pond in despair. Then, his eyes opened wide, for he saw his reflection. To his great astonishment, the ugly duckling discovered that he was a beautiful, royal swan! The swans welcomed their new friend, whose lovely appearance was matched only by his kind heart. He now felt like he belonged.
Read the fairy tale The Princess and the Pea.
Once upon a time, there was a handsome prince. The prince lived with his mother and father in a luxurious castle that overlooked a valley of wildflowers and a distant forest. As the prince grew up, he began to long for a princess. However, the prince wanted to be sure that the princess was a real princess. The queen and king searched far and wide for a real princess, but the prince always found something wrong with the princesses they found.
One evening, there was a terrible storm. The wind howled, thunder shook the stone walls, and lightning filled the dark night sky. Through the pelting of the rain, there came a knock at the door. When the king opened the door, he saw a bedraggled girl, soaked to the skin and covered in mud. He ushered her into the castle so that she could warm herself by the fire.
"Why is a young servant girl like you wandering about on such a ferocious night?" queried the king.
The disheveled maiden looked at the king in disbelief. "I am a princess, come to see the prince," she explained, all the while shivering.
The king summoned his wife, the queen, for advice. The queen looked at the hideous creature in disbelief, thinking that no princess would ever allow herself to be found in such a state. She thought quickly and came up with a clever plan. The queen put a small pea at the bottom of a bed and piled twenty mattresses on top of it. When the girl arrived at the room, she had to climb a ladder to reach the top of the bed, where she collapsed in exhaustion.
Bright and early the next morning, the king and queen arrived at the girl's bedchamber. The queen asked the girl how she had slept the night before.
"Absolutely terribly!" bemoaned the maiden. "I have spent the entire night tossing and turning. I don't know whether there is something hard in the bed, or your mattresses are rocks, but my body is black and blue."
The queen and the king stared at the maiden in astonishment. Only a real princess would have such delicate skin that she could feel a pea under twenty mattresses. The queen and king brought her to the prince, who was thrilled to meet a real princess with such an independent spirit.
How do the authors use similar and different events in each fairy tale to illustrate the theme that people should not be judged based on their appearances? Use complete sentences and evidence from the text to support your answer.
Answers
Answer:
MAIN IDEA
What the authors meant is not to judge people by their looks.
_____________________________________________________________
THE UGLY DUCKLING
The ugly duckling doesn't fit with the other ducklings and grows up, to be a fabulous bird. In the beginning, he is teased because of his looks, in a quote, "As the ugly duckling grew, many animals in the pond criticized him. His feathers were too dark, his neck was too long, and his body was too big. His fellow ducklings refused to recognize that underneath the feathers, the ugly duckling was kind, good, and gentle. The ugly duckling shed many tears because none of the other animals would play with him."
Near the end, however, it states, "He believed that the swans would never be his friends and looked down into the pond in despair. Then, his eyes opened wide, for he saw his reflection. To his great astonishment, the ugly duckling discovered that he was a beautiful, royal swan! The swans welcomed their new friend, whose lovely appearance was matched only by his kind heart. He now felt like he belonged." Throughout the course of the story, the other birds' views change since now they realize how awful they felt for mistreating the ugly duckling.
_____________________________________________________________
THE PRINCESS AND THE PEA
The king and queen didn't believe that she was a princess, so they had her endure the trial of sleeping on twenty mattresses with a pea under the very bottom one. Near the beginning of the story, it states, "The disheveled maiden looked at the king in disbelief. "I am a princess, come to see the prince," she explained, all the while shivering. The king summoned his wife, the queen, for advice. The queen looked at the hideous creature in disbelief, thinking that no princess would ever allow herself to be found in such a state. She thought quickly and came up with a clever plan. The queen put a small pea at the bottom of a bed and piled twenty mattresses on top of it. When the girl arrived at the room, she had to climb a ladder to reach the top of the bed, where she collapsed in exhaustion." This is when the king and queen were in doubt that she was a princess.
However later on it stated, "Bright and early the next morning, the king and queen arrived at the girl's bed-chamber. The queen asked the girl how she had slept the night before. "Absolutely terribly!" bemoaned the maiden. "I have spent the entire night tossing and turning. I don't know whether there is something hard in the bed, or your mattresses are rocks, but my body is black and blue." The queen and the king stared at the maiden in astonishment. Only a real princess would have such delicate skin that she could feel a pea under twenty mattresses. The queen and king brought her to the prince, who was thrilled to meet a real princess with such an independent spirit." As you can see the king and queen believed that she was a princess now because they stated, "Only a real princess would have such delicate skin that she could feel a pea under twenty mattresses."
_____________________________________________________________
CONCLUSION
Both stories focus on how the main character is doubted or mistreated because of how they look, but throughout the stories, the main character proves them wrong.
Explanation:
Have a great rest of your day
#TheWizzer
Explain the difference between a covalent bond formed between two atoms of the same element and a covalent bond between two atoms of two different elements.
Answers
Answer:
Polarity
Explanation:
Covalent bonds between two atoms of the same element (diatomics) are nonpolar because neither atom is more electronegative. Covalent bonds between atoms of two different elements are often polar and must be polar to some extent because of differences in electronegativity between the two atoms involved.
Hydrogen bromide is a gas in room temperature. It is soluble in water, forming hydrobromic acid. Identify the conjugate acid-base pairs.
HBr (g) + H₂O (1)→ H₂O* (aq) + Br (aq)
Select one:
O a. HBr-H₂O and H₂O* - Br
b. HBr-H₂O* and H₂O - Br
c. HBr-Br and H₂O-OH-
d. HBr-Br-and H₂O-H₂O*
Answers
The correct answer is option d. HBr-Br and H2O-H3O+ HBr and Br- form a conjugate acid-base pair, and H2O and H3O+ form another conjugate acid-base pair. The formation of hydrobromic acid (HBr) from HBr gas and water involves the transfer of a proton, leading to the formation of the conjugate acid (H3O+) and conjugate base (Br-).
In the given reaction, the following conjugate acid-base pairs can be identified: HBr (acid) and Br- (base)
HBr acts as an acid by donating a proton (H+) to form the bromide ion (Br-). This is the conjugate base of HBr.
H2O (base) and H3O+ (acid)
H2O acts as a base by accepting a proton (H+) to form the hydronium ion (H3O+). This is the conjugate acid of H2O.
For more question on conjugate
https://brainly.com/question/14684465
#SPJ8
What is Keq for the reaction N₂ + 3H2 = 2NH3 if the equilibrium
concentrations are [NH3] = 3 M, [N₂] = 2 M, and [H₂] = 1 M?
Answers
The equilibrium constant, Keq, for the reaction is 13.5.
What is Keq for a reaction?The equilibrium constant, Keq, for a reaction is the value of a chemical reaction's reaction quotient at chemical equilibrium, which is a condition that a dynamic chemical system approaches when enough time has passed and at which its composition has no discernible tendency to change further.
For a reaction: A + B ⇆ C + D
Keq = [C] [D] / [A] [B]
For the given reaction, N₂ + 3 H₂ ⇆ 2 NH₃
where the equilibrium concentrations are;
[N₂] = 2 M
[H₂] = 1
[NH₃] = 3
Keq; 3³ / (2 * 1³)
Keq = 13.5
Learn more about equilibrium concentration at: https://brainly.com/question/19340344
#SPJ1
separating mixtures: filtration
Answers
hi these are the answers :)
Draw the resonating structures of acetophenone and discuss whether it is o&p or m –directing and why?
Answers
The resonating structures of acetophenone can be drawn by considering the movement of electrons. Acetophenone has a ketone group (C=O) attached to a phenyl ring.
Acetophenone is an o&p-directing group. This means that it directs incoming substituents to the ortho and para positions on the phenyl ring during electrophilic aromatic substitution reactions.
The o&p-directing effect is attributed to the resonance stabilization provided by the delocalized π electrons of the phenyl ring. T
he ortho and para positions on the ring have more electron density due to the delocalization, making them more attractive for electrophilic attack.
To further illustrate, let's consider the addition of a substituent, such as a halogen, to acetophenone. The halogen would preferentially substitute at the ortho or para positions rather than the meta position.
In summary, acetophenone exhibits o&p-directing behavior in electrophilic aromatic substitution reactions due to the resonance stabilization provided by the delocalized π electrons in the phenyl ring. This makes the ortho and para positions more reactive and attractive for electrophilic attack compared to the meta position.
To know more about acetophenone visit:
brainly.com/question/16031977
#SPJ11
The model of the atom changed as new evidence was discovered. The plum pudding model suggested that the atom was a ball of positive charge with electrons embedded in it. Evidence from the alpha particle scattering experiment led to a change in the model of the atom from the plum pudding model. Explain how. PLS HELP RN :)
Answers
Answer:
so since the model atom was changed as new evidence, and the plum pudding model was a ball of positive charge, the alpha particle scattering which broke up the atom
The
percent yield for the reaction in which 15.6 g of aluminum
hydroxide is reacted in excess hydrogen chloride gas is 92.5
%. What is the actual yield of aluminum chloride?
Answers
Answer:
24.6
Explanation:
what is a conclusion that ernest rutherford made after his experiments with alpha particles and gold foil?
Answers
Rutherford's -particle scattering experiment provides the empirical support for drawing the inference that the majority of atomic space is empty.
what is gold foil experiment?
Rutherford described the gold-foil experiment.
The α-particles in his experiment were made to land on a thin piece of gold foil.
The gold foil was linearly penetrated by the majority of the α-particles.
A few of the particles made slight angular deviations.
Every 12000 particles, one of them seemed to bounce.
Rutherford's atomic model's conclusion
The majority of the -particles went through the gold foil without deflecting, leaving essentially no space inside the atom.
Since the positive charge takes up the smallest amount of space, very few particles are likely to have been deflected off their course.
Indicating that all of the positive charge and mass of the gold atom were concentrated in a very compact volume within the atom, a very small percentage of -particles were redirected by 180°.
To learn more about gold foil experiment https://brainly.com/question/4091109
#SPJ4
I’ll mark you brainlist plz
Answers
Answer:
I think nuetron stars
Explanation:
write a 3 sentence summary about DNA.
I’ll mark you as the brainiest answer !!
Answers
Answer:
DNA is a complex, long-chained molecule. DNA contains the genetic blueprint for building and maintaining all living organisms. Found in nearly all cells, DNA carries the instructions needed to create proteins, specific molecules essential to the development and functioning of the body.
Taylor saw a raccoon in her backyard last weekend. She put
out some food and a bowl with 360 milliliters (ml) of water in
it. The raccoon ate all the food and drank 1/3 of the water.
How much water did the raccoon drink?
Answers
Answer:
The raccoon drank 120 ml of water.
Explanation:
All you have to do is take the 360 ml of water and to find what 1/3 of it is you divide 360 by 3 to get 120 ml of water.
Hope that helps and have a great day!
To find the answer you would multiply 360 by 1/3 or divide 360 by 3.
360/3=120
Question 30 (10 points) All unauthorized experiments are prohibited . O True False
Answers
Answer:
All unauthorized experiments are prohibited. You are allowed to enter the chemical preparation/storage area any time you need to get an item. Laboratory aprons should be worn during all lab activities. It's okay to pick up broken with our bare hand as long as the glass is placed in the trash.
Explanation:
Extended response question: The following reaction is exothermic: H2 (g) + F2 (g) → 2HF (g) Draw a reaction profile to show this reaction, to include the relative energies of the reactants and products, the activation energy and the overall energy change. (6)
Answers
The reaction profile as required in the question is shown in the image attached.
What is an exothermic reaction?Chemical reactions that emit heat into their surroundings are known as exothermic reactions. The total energy of the reactants is greater than the total energy of the products in an exothermic process. The extra energy is consequently released as heat.
We can see from the reaction profile that we have here that energy is given off in the reaction and this can be shown by the curve that is in the image attached.
Learn more about exothermic reaction:https://brainly.com/question/28546817
#SPJ1
25cm^3 of 0.1 mol/dm^3 hydrochloric acid exactly neutralise 20cm^3 of aqueous sodium hydroxide.
the equation for this reaction is :
NaOH + HCL ------> NaCl + H20
what is the concentration of the sodium hydroxide solution?
A. 0.080
B. 0.800
C. 0.125
D. 1.25
(please solve with explanation!!)
Answers
Answer:
Expert Verified AnswerExplanation:
The concentration of the sodium hydroxide solution can be calculated by using the balanced chemical equation for the reaction.
1 mole of NaOH reacts with 1 mole of HCl to form 1 mole of NaCl and 1 mole of H2O.
Since 25 cm^3 of 0.1 mol/dm^3 HCl neutralizes 20 cm^3 of NaOH, the number of moles of NaOH present in the solution can be calculated as follows:
0.1 mol/dm^3 HCl * (25 cm^3)/(1000 cm^3/dm^3) = 0.0025 moles HCl
So, the number of moles of NaOH present in 20 cm^3 of the solution is 0.0025 moles.
Finally, the concentration of the NaOH solution can be calculated as follows:
(0.0025 moles NaOH)/(20 cm^3) * (1000 cm^3/dm^3) = 0.125 mol/dm^3
Therefore, the concentration of the sodium hydroxide solution is 0.125 mol/dm^3 (Option C).
What does the graph say about the relationship between pressure and volume in a gas?
Select the correct answer from each drop-down menu.
As the gas volume increases, the pressure
proportional to the volume.
The pressure in a gas is
Answers
Answer: The pressure of gas is inversely proportional to volume of the gas.
Explanation: A pressure-volume graph for gases demonstrates the relationship between pressure and volume. When the volume decreases, the pressure increases (inverse relationship) and vice versa. The graph visually represents the behavior of gases during compression or expansion processes. The slope of the line on the graph indicates the gas's compressibility. Analyzing the graph provides insights into gas properties and processes, such as Boyle's Law or the ideal gas law, in a concise and graphical manner.
Therefore the answer is pressure decrease as volume increase.
While camping you light a small campfire, initiating the combustion of wood to produce heat and
light. What can you determine about this reaction?
O A. It is exothermic.
B. The bond making energy is more than 600 kJ.
OC. It is endothermic.
D. The bond breaking energy is more than 600 kJ.
Answers
Answer:
A. It is exothermic
Explanation:
Combustion is a chemical reaction in which a substance combines with oxygen present in air to produce carbon (iv) oxide and water as well release heat and light energy.Combustion is an exothermic process.
An exothermic reaction releases energy in the form of heat to the surroundings. The energy required to break bonds in the reactants is less than the energy required to form new bonds in the products in an exothermic reaction.
From the given options;
A. It is exothermic is determinable since the reaction is a combustion reaction
B. The bond making energy is more than 600 kJ is not certain because the mass of the wood being burnt is not given. Also, wood is not composed of a specific element that would be taking part in the reaction, rather it is composed of various substances.
C. It is endothermic. is wrong because combustion of wood is exothermic.
D. The bond breaking energy is more than 600 kJ is not certain because the mass of the wood being burnt is not given. Also, wood is not composed of a specific element that would be taking part in the reaction, rather is composed of many substances.