Question

1. stem a chemical reaction is endothermic if it absorbs heat from its surroundings. it is exothermic if it gives off heat to its surroundings. in her chemistry class, lily is given a salt (ammonium nitrate) and a beaker of water at 60 °f. she dissolves the salt in the water and sees that the temperature of the solution is now 50 °f. did the temperature of the solution increase or decrease? by how many degrees? what kind of reaction has occurred? explain.
2. at the beginning of the month, joe has $180 in his bank account. he wants to buy a new gaming system for $250 in two weeks. his parents have offered to loan him money if he needs it. he gets $20 a week for an allowance. will he have enough money at the end of two weeks to make the purchase on his own? if not, how much will he have to borrow from his parents? explain.
3. reason can you ever add two positive integers and get a negative integer? explain.
4. reason can you subtract a positive integer from a positive integer and get a negative result? explain your answer.

Explanation:

3.

Step1: Determine temperature change

Initial temperature is 60°F and final is 50°F. Calculate the difference: $60 - 50=10$.

Step2: Identify reaction type

Since the temperature of the solution decreased, heat was absorbed by the reaction from the surroundings. So it is an endothermic reaction.

Step1: Calculate total money after two - weeks

Joe starts with $180 and gets $20 per week for 2 weeks. The money from allowance is $20\times2 = 40$. The total money he has is $180 + 40=220$.

Step2: Compare with the cost of gaming - system

The cost of the gaming - system is $250. Since $220<250$, he doesn't have enough money.

Step3: Calculate the amount to borrow

The amount he needs to borrow is $250 - 220 = 30$.

Positive integers are numbers greater than zero. When adding two positive numbers, we are combining quantities that are greater than zero, resulting in a larger quantity greater than zero.

Answer:

The temperature of the solution decreased by 10°F. The reaction is endothermic because it absorbed heat from the surroundings causing the temperature of the solution to drop.

4.