Question

prelaboratory assignment

1. provide the key - term that corresponds to each of the following definitions.

(a) matter having an indefinite composition and properties that can vary within the sample
(b) matter having a definite composition but properties that can vary from sample to sample; examples include alloys and solutions
(c) matter having constant composition with definite and predictable properties
(d) a pure substance that can be broken down into two or more simpler substances by chemical reaction
(e) a pure substance that cannot be broken down any further by chemical reaction
(f) a characteristic of the substance that can be observed without changing its chemical formula
(g) a characteristic of a substance that cannot be observed without changing its chemical formula
(h) a modification of a substance that does not alter its chemical composition
(i) a modification of a substance that alters its chemical composition
(j) an insoluble solid substance produced from a reaction in aqueous solution
key terms: chemical change, chemical property, compound, element, heterogeneous mixture, homogeneous mixture, physical change, physical property, precipitate, substance

1. classify the following characteristics as a physical (phys) or chemical (chem) property.

(a) physical state (b) density
(c) melting point (d) hardness
(e) appearance (f) reactivity
(g) solubility (h) conductivity

1. classify the following observations as a physical (phys) or chemical (chem) change.

(a) candle burning (b) wax melting
(c) alcohol vaporizing (d) antacid fizzing in water
(e) apple turning brown (f) steam condensing on a mirror
(g) fire releasing heat (h) fireworks releasing light

Explanation:

1.
(a) Heterogeneous mixture has indefinite composition and variable properties within the sample.
(b) Homogeneous mixture has a definite composition but properties can vary from sample to - sample.
(c) Substance has constant composition with definite and predictable properties.
(d) Compound is a pure substance that can be broken down into simpler substances by chemical reaction.
(e) Element is a pure substance that cannot be broken down further by chemical reaction.
(f) Physical property can be observed without changing the chemical formula.
(g) Chemical property cannot be observed without changing the chemical formula.
(h) Physical change does not alter the chemical composition.
(i) Chemical change alters the chemical composition.
(j) Precipitate is an insoluble solid produced from a reaction in aqueous solution.

1. Physical state, density, melting point, hardness, appearance, solubility, and conductivity are physical properties as they can be observed without changing the chemical nature of the substance. Reactivity is a chemical property as it involves chemical reactions.
2. Wax melting, alcohol vaporizing, steam condensing on a mirror are physical changes as they only involve changes in physical state without altering the chemical composition. Candle burning, antacid fizzing in water, apple turning brown, fire releasing heat, fireworks releasing light are chemical changes as new substances are formed and chemical reactions occur.

Answer:

1.
(a) Heterogeneous mixture
(b) Homogeneous mixture
(c) Substance
(d) Compound
(e) Element
(f) Physical property
(g) Chemical property
(h) Physical change
(i) Chemical change
(j) Precipitate
2.
(a) phys
(b) phys
(c) phys
(d) phys
(e) phys
(f) chem
(g) phys
(h) phys
3.
(a) chem
(b) phys
(c) phys
(d) chem
(e) chem
(f) phys
(g) chem
(h) chem