1. What is the term for a pure substance that can be broken down into two or mor

Question

1.     What is the term for a pure substance that can be broken down into two or more substances by chemical reaction? A) compound B) element C) homogeneous D) matter E) none of the above

2.     Which of the following describes a substance in the gaseous physical state? A) The substance has a variable shape. B) The substance has a variable volume. C) The substance compresses significantly. D) all of the above E) none of the above

3-.     Air contains nitrogen, oxygen, argon, and other gases. Which of the following describes air? A) compound B) element C) heterogeneous mixture D) homogeneous mixture E) none of the above

4.     According to the kinetic theory, what happens to the kinetic energy and velocity of gaseous particles when the temperature decreases? A) Kinetic energy increases and velocity decreases. B) Kinetic energy decreases and velocity increases. C) Kinetic energy and velocity increase. D) Kinetic energy and velocity decrease. E) Kinetic energy and velocity remain constant.

5-.     Ethyl alcohol always contains 52% carbon, 13% hydrogen, and 35% oxygen by mass. What law is illustrated by this statement? A) law of conservation of mass B) law of constant composition C) law of constant percentages D) law of multiple proportions E) none of the above

Explanation / Answer

1) A - Anything which can be broken down as a result of chemical reaction is called compound.

2) D - These are the basic properties of gaseous state: variable shape, variable volume and can be compressed

3) C - its a heterogenous mixture because these gases can be monoatomic, diatomic or poly atomic.

4) E - when we lower the temperature, it's kinetic energy and velocity are always constant because velocity is speed with direction, in gases any particle has velocity zero, because it moves with equal speed in every direction.

So we have zero velocity for every particle and hence zero kinetic energy, as the overall velocity sums to be zero.

5) E - The actual law is "law of definite proportion". according to which : Different samples of a pure compound always contains the same proportions of elements by mass

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