Question

1. classify the following as a chemical change (c) or a physical change (p). (2 pts)

a. chopping wood
b. burning wood
c. an apple oxidizing
d. steam from a shower

1. classify the following as an element, compound, homogeneous mixture, or heterogeneous mixture. (2 pts)

a. sodium chloride
b. neon
c. bronze
d. pure water

1. you are in lab trying to determine the identity of an unknown pure substance. the chart to the right shows a list of observations you have made. on your answer sheet, categorize the observations as physical and chemical properties. then explain the reasoning behind your overall differentiation. (6 pts)

observations:
a. it melts at 450°c.
b. it is a solid at room temperature.
c. it decomposes in the presence of oxygen.
d. it is shiny.
e. it is 9.4 cm long.
f. it has a mass of 301 g.
g. it is magnetic.
h. it readily reacts with hydrogen gas.

1. iron and oxygen react to form rust. answer the following questions based on this.

a. is this a physical or chemical change? explain how you know. (2 pts)
b. if you started with 60 g of iron and 15 g of oxygen, what should be the mass of the rust if it reacts completely? justify your answer with reasoning. (3 pts)

Explanation:

33.
a. Chopping wood is a physical change (P) as it only changes the shape and size of wood without altering its chemical composition.
b. Burning wood is a chemical change (C) because it involves a chemical reaction with oxygen to form new substances like carbon - dioxide and ash.
c. An apple oxidizing is a chemical change (C) as it involves a chemical reaction between the apple's substances and oxygen in the air.
d. Steam from a shower is a physical change (P) as it is a phase change from liquid water to gaseous water vapor without a change in chemical composition.

34.
a. Sodium chloride is a compound as it is made up of two different elements (sodium and chlorine) chemically bonded together.
b. Neon is an element as it is a pure substance made of only one type of atom.
c. Bronze is a homogeneous mixture as it is an alloy of copper and other metals with a uniform composition throughout.
d. Pure water is a compound as it is composed of hydrogen and oxygen atoms chemically bonded in a fixed ratio.

35.
Physical properties: a. It melts at 450°C; b. It is a solid at room temperature; d. It is shiny; e. It is 9.4 cm long; f. It has a mass of 301 g; g. It is magnetic. These properties can be observed or measured without changing the chemical identity of the substance.
Chemical properties: c. It decomposes in the presence of oxygen; h. It readily reacts with hydrogen gas. These properties describe how the substance undergoes a chemical change or reaction.

36.
a. It is a chemical change. We know this because a new substance (rust, which is iron oxide) is formed when iron and oxygen react.
b. According to the law of conservation of mass, the total mass of reactants equals the total mass of products. The mass of iron is 60 g and the mass of oxygen is 15 g. So the mass of rust should be 60 g+ 15 g = 75 g if the reaction is complete.

Answer:

33.
a. P
b. C
c. C
d. P
34.
a. Compound
b. Element
c. Homogeneous mixture
d. Compound
35.
Physical properties: a, b, d, e, f, g
Chemical properties: c, h
36.
a. Chemical change. Reason: New substance (rust) formed.
b. 75 g. Reason: Law of conservation of mass.