Question

multiple choice. choose the one alternative that best completes the statement or answers the question.

1. which of the following statements about compounds is true?

a) a substance that is not as common as pure elements.
b) a substance composed of two or more elements in fixed, definite proportions.
c) a substance that cannot be broken down into simpler substances.
d) a pure substance that has variable composition throughout.
e) none of the above

1. physical properties are:

a) those that cause atoms and molecules to change.
b) those that a substance displays without changing its composition.
c) those that a substance displays only through changing its composition.
d) identical for all solid matter.
e) none of the above

1. which statement below best describes the process of the paint on a vehicle fading over time?

a) chemical change because the paint molecules are changing composition.
b) chemical change because the paint molecules have changing phases.
c) physical change because the paint molecules have risen to the surface of the clear coat.
d) physical change because the paint molecules are still paint molecules.
e) none of the above

1. which state of matter has atomic spacing that is close together and indefinite shape?

a) plasma
b) solid
c) gas
d) liquid
e) none of the above

1. what is the value of 27°c on the kelvin temperature scale?

a) 300
b) 81
c) 273
d) 246
e) none of the above

1. what is the specific heat (j/g°c) of a metal object whose temperature increases when 38.5 j of heat was added to 10.0 g of metal?

a) 4.18
b) 1.4
c) 0.15
d) 0.73
e) none of the above

1. how many calories are there in a 255 calorie snack - bar?

a) 1.07 x 10³
b) 2.55 x 10⁵
c) 1 x 10³
d) 60.9
e) none of the above

Explanation:

Step1: Recall compound definition

A compound is a substance composed of two or more elements in fixed, definite proportions.

Step2: Recall pure - substance definition

A pure substance can be an element or a compound and has a constant composition.

Step3: Recall physical - property definition

Physical properties are those that a substance displays without changing its composition.

Step4: Analyze paint - fading process

Paint fading over time is a chemical change because the paint molecules are changing composition (e.g., due to oxidation).

Step5: Recall states - of - matter properties

Liquids have atomic spacing that is close together and indefinite shape.

Step6: Convert Celsius to Kelvin

The conversion formula is $K = ^{\circ}C+ 273$. For $27^{\circ}C$, $K=27 + 273=300$.

Step7: Recall calorie - Calorie conversion

1 Calorie = 1000 calories. So, 255 Calories = 255×1000 = 2.55×10⁵ calories.

Answer:

1. C
2. C
3. A
4. D
5. A
6. B