The statement that is true about magnets is ''Similar poles of a magnet repel each other.''
<h3>What are the characteristics of magnet?</h3>
All magnets have both north and south poles. Opposite poles attract each other, whereas the similar poles repel each other. When you rub a piece of iron along a magnet, this force creates a magnetic field.
So we can conclude that The statement that is true about magnets is ''Similar poles of a magnet repel each other.''
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Answer:
In 4 years the carbon monoxide level reach 7.8 parts per million.
Explanation:
The average daily level of carbon monoxide in the air is given by :
parts per million..[1]
The population of the region after t years is modeled by the formula :
...[2]
If level of carbon monoxide level reach 7.8 parts per million in t years.
Using [1] to calculate value of x.
c(x)= 7.8 parts per million
c(x) = 0.5x + 2 parts per million
7.8 parts per million = (0.5x + 2 ) parts per million
Solving for x , we get ;
x = 11.6
Using [2] to calculate value of t.:
x(t) = 11.6

Solving for 't' we get ;
t = 4 years
In 4 years the carbon monoxide level reach 7.8 parts per million.
Answer:
The crushed tablet dissolves fastest among the three forms.
Explanation:
The experiment is aimed at determining the effect of surface area of reactants on reaction rate.
Sodium bicarbonate tablets are provided and divided into three groups of consisting of three trials each. The temperature of the water is kept constant at 20°C. The first group consists of three tablets of sodium bicarbonate dissolved in individual trials in water. The second group consists of three quarter tablets of sodium bicarbonate dissolved in individual trials in water. The third group consists of three crushed tablets of sodium bicarbonate dissolved in individual trials in water.
The results shows that the average time for the dissolution of the first group is 51 seconds; the second group is 42 seconds while the third group is 17 seconds.
Therefore, it can be concluded that increasing the surface area of reactants increases the rate of reaction. This is because more reactant molecules are exposed for dissolution by water with increase in surface area.
Answer:
Calcium nitrate is soluble in water and dissociate into ions whereas calcium carbonate is insoluble and water and do not form ions.
Explanation:
An electrolyte is a substance which conducts electricity in molten form or when dissolved in water.
The ability of an electrolyte to conduct electricity is due the movement of charged particles called ions. The ions are of two types: negatively charged ions called anions and positively charged ions called cations.
Calcium nitrate is a soluble in water, and when dissolved in water produces two ions; negatively charged nitrate ions,NO₃⁻, and positively charged calcium ions, Ca²⁺. These ions enable it to conduct electricity.
Calcium carbonate on the other hand is insoluble in water, and thus, do not produces any ions capable of carrying current.