D)By increasing or decreasing the size of systems that are difficult to study we make it easier for students to see how they work and therefore make it easier for them to learn.
Explanation:
Scientific models makes it easier to teach students about systems because their sizes can be adjusted and this makes it easier for students to see how they work. 
A model is a simplification of the real work. It takes a part of the real world and studies it. 
Models are highly desired in teaching and understanding very complex systems. 
- Since a tutor owns the control of the model, they can make adjustments on them to a scale that is convenient to work with. 
- Also, a part of a system can be studied one at a time making it simple for students to comprehend. 
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To find for the oxidizing agent, first let us write the
half reactions of this complete chemical reaction:
Ca = Ca2+ + 2e- <span>
2 H+ + 2e- = H2</span>
 
The oxidizing agent
would be the substance of the element that is reduced. We know that an element
is reduced when an electron is added to it. In this case, the element being
reduced is H. Therefore the oxidizing agent is HNO3.
 
Answer:
<span>HNO3</span>
 
        
                    
             
        
        
        
Answer:  Bacteria from the fecal transplant can fill up the space in the gut, limiting the food and space for invading harmful bacteria.fecal transplants may be best answer to antibiotic-resistant bacteria: Non-pharmaceutical treatment combats recurring Clostridium Difficile infections 
Explanation:
 
        
             
        
        
        
If you are comparing 2 metals, the metal with a higher <u>Number of free ions</u> will react with EDTA first 
<h3>What is EDTA ?</h3>
EDTA is a type of chemical which binds certain metal ions such as calcium and magnesium. some of the functions of EDTA  includes:
- Preventing blood clotting of blood samples
- prevention of the formation of Biofilm by bacterias
The EDTA will readily react with metals which have a hiogher number of free ions that it can bind with. 
Hence we can conclude that If you are comparing 2 metals, the metal with a higher <u>Number of free ions</u> will react with EDTA first. 
Learn more about EDTA : brainly.com/question/10818175
 
        
             
        
        
        
Answer:
485.76 g of CO₂ can be made by this combustion
Explanation:
Combustion reaction:
2 C₄H₁₀(g) + 13 O₂ (g) → 8 CO₂ (g) + 10 H₂O (g)
If we only have the amount of butane, we assume the oxygen is the excess reagent.
Ratio is 2:8. Let's make a rule of three:
2 moles of butane can produce 8 moles of dioxide
Therefore, 2.76 moles of butane must produce (2.76 . 8)/ 2 = 11.04 moles of CO₂
We convert the moles to mass → 11.04 mol . 44g / 1 mol = 485.76 g