Q: A student heats 100 g of water from 20°C to 80°C. If the specific heat capacity of water is $$4.18\ J/g\cdot\degree C$$, how much heat is absorbed by the water?

$$q = 100\ g \times 4.18\ J/g\cdot\degree C \times (80\degree C - 20\degree C) = 25,080\ J$$

Q: Convert 225 Cal (nutritional Calories) to joules. Use $$1\ Cal = 1000\ cal$$ and $$1\ cal = 4.184\ J.$$

$$225\ Cal \times 1000\ cal/Cal \times 4.184\ J/cal = 941,400\ J$$

Q: A 3.10 g copper penny warms from $$-5.0\degree C to$$ $$37.0\degree C. If $$the specific heat capacity of copper is $$0.385\ J/g\cdot\degree C$$, how much heat is absorbed?

$$q = 3.10\ g \times 0.385\ J/g\cdot\degree C \times (37.0\degree C - (-5.0\degree C)) = 50.1\ J$$

Q: A sample of water absorbs $$5.78 \times 10^3$\ J of $$heat. If the mass is $$328\ g$$ and the specific heat capacity is $$4.18\ J/g\cdot\degree C$$, what is the change in temperature?

$$\Delta T = \frac{5.78 \times 10^3$\ J}{328\ g \times 4.18\ J/g\cdot\degree C} = 4.21\degree C$$

Question 1

Which of the following best describes a compound?

Accepted Answer

A substance composed of two or more elements chemically combined in a fixed ratio.

Question 2

A student heats 100 g of water from 20°C to 80°C. If the specific heat capacity of water is $$4.18\ J/g\cdot\degree C$$, how much heat is absorbed by the water?

Accepted Answer

$$q = 100\ g 	imes 4.18\ J/g\cdot\degree C 	imes (80\degree C - 20\degree C) = 25,080\ J$$

Question 3

Which process is an example of a chemical change?

Accepted Answer

Iron rusting when exposed to air.

Question 4

A mixture of sand and water can best be separated by which method?

Accepted Answer

Filtration

Question 5

Which statement about the law of conservation of mass is correct?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 6

Convert 225 Cal (nutritional Calories) to joules. Use $$1\ Cal = 1000\ cal$$ and $$1\ cal = 4.184\ J.$$

Accepted Answer

$$225\ Cal 	imes 1000\ cal/Cal 	imes 4.184\ J/cal = 941,400\ J$$

Question 7

Which of the following is a homogeneous mixture?

Accepted Answer

Seawater

Question 8

A 3.10 g copper penny warms from $$-5.0\degree C to$$ $$37.0\degree C. If $$the specific heat capacity of copper is $$0.385\ J/g\cdot\degree C$$, how much heat is absorbed?

Accepted Answer

$$q = 3.10\ g 	imes 0.385\ J/g\cdot\degree C 	imes (37.0\degree C - (-5.0\degree C)) = 50.1\ J$$

Question 9

Which of the following statements about energy is FALSE?

Accepted Answer

Perpetual motion machines are possible because energy can be created.

Question 10

Which temperature is identical on both the Celsius and Fahrenheit scales?

Accepted Answer

$$-40\degree$$

Question 11

Which of the following is a physical property?

Accepted Answer

Boiling point of water

Question 12

A chemical cold pack absorbs heat from its surroundings. Which type of reaction is this?

Accepted Answer

Endothermic

Question 13

Which statement best explains why coastal cities have more moderate temperatures than inland cities?

Accepted Answer

Water has a high specific heat capacity, so it absorbs and releases heat slowly.

Question 14

Which of the following is NOT a pure substance?

Accepted Answer

Brass

Question 15

A sample of water absorbs $$5.78 	imes 10^3$\ J of $$heat. If the mass is $$328\ g$$ and the specific heat capacity is $$4.18\ J/g\cdot\degree C$$, what is the change in temperature?

Accepted Answer

$$\Delta T = \frac{5.78 	imes 10^3$\ J}{328\ g 	imes 4.18\ J/g\cdot\degree C} = 4.21\degree C$$

Question 16

Which of the following is a correct conversion from Celsius to Kelvin?

Accepted Answer

$$K = \degree C + 273.15$$

Question 17

Which statement about the states of matter is correct?

Accepted Answer

Solids have a definite shape and volume and are incompressible.

Question 18

A rock of mass $$14.3\ g$$ absorbs $$174\ J of $$heat and its temperature rises from $$25\degree C to$$ $$52\degree C. $$What is its specific heat capacity?

Accepted Answer

$$C = \frac{174\ J}{14.3\ g 	imes (52\degree C - 25\degree C)} = 0.45\ J/g\cdot\degree C$$

Question 19

Which of the following is a characteristic of an amorphous solid?

Accepted Answer

Atoms or molecules do not have a long-range order.

Question 20

Which unit would result in the lowest numerical value for an appliance's yearly energy consumption?

Accepted Answer

Kilowatt-hours (kWh)

Chapter 3: Matter and Energy – Introduction to Chemistry Study Notes

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