Question

1. label each of the following as an element, compound, homogeneous mixture or heterogeneous mixture. terms may be used once, more than once or not at all. (8)

a. oxygen (o₂)
b. vinegar (acetic acid and water)
c. gold (au)
d. concrete
e. salt water
f. sodium bicarbonate (nahco₃)
g. soil
h. hydrogen peroxide (h₂o₂)

1. describe how the shape and volume of water changes as it is heated from 0°c to 100°c. note: water freezes at 0°c and boils at 100°c. (3)

1. label each of the following as a physical property, physical change, chemical property or chemical change. terms may be used once, more than once or not at all. (8)

a. iron rusting
b. melting of ice
c. boiling point of water
d. baking bread
e. dissolving salt in water
f. flammability of gasoline
g. chopping wood
h. photosynthesis in plants

Explanation:

Step1: Recall definitions

An element is a pure - substance made of only one type of atom. A compound is a pure - substance made of two or more different types of atoms chemically combined. A homogeneous mixture has a uniform composition throughout, and a heterogeneous mixture has a non - uniform composition.

Step2: Classify a. Oxygen ($O_2$)

Oxygen is a pure substance made of only oxygen atoms. It is an element.

Step3: Classify b. Vinegar (acetic acid and water)

Vinegar has a uniform composition of acetic acid and water throughout, so it is a homogeneous mixture.

Step4: Classify c. Gold (Au)

Gold is a pure substance made of only gold atoms. It is an element.

Step5: Classify d. Concrete

Concrete has a non - uniform composition with different components like cement, sand, and gravel, so it is a heterogeneous mixture.

Step6: Classify e. Salt water

Salt water has a uniform composition of salt dissolved in water, so it is a homogeneous mixture.

Step7: Classify f. Sodium bicarbonate ($NaHCO_3$)

Sodium bicarbonate is made of sodium, hydrogen, carbon, and oxygen atoms chemically combined. It is a compound.

Step8: Classify g. Soil

Soil has a non - uniform composition with different particles like sand, clay, and organic matter, so it is a heterogeneous mixture.

Step9: Classify h. Hydrogen peroxide ($H_2O_2$)

Hydrogen peroxide is made of hydrogen and oxygen atoms chemically combined. It is a compound.

for question 14:

Step1: Consider the states of water

Water is in a solid state (ice) at 0°C, a liquid state between 0°C and 100°C, and a gas state (steam) at 100°C.

Step2: Analyze shape change

As ice (solid), it has a definite shape. As it melts to a liquid, it takes the shape of its container. As it boils to a gas, it fills the entire volume of its container.

Step3: Analyze volume change

When ice melts to liquid water, its volume decreases slightly. As liquid water is heated to 100°C and turns into steam, its volume increases significantly.

for question 15:

Step1: Recall definitions

A physical property is a characteristic of a substance that can be observed without changing the substance's chemical identity. A physical change is a change in the form or state of a substance without changing its chemical composition. A chemical property is a characteristic that describes how a substance changes into a different substance. A chemical change is a change in which a substance is transformed into a chemically different substance.

Step2: Classify a. Iron rusting

Iron reacts with oxygen and water to form iron oxide (rust), a new substance. So it is a chemical change.

Step3: Classify b. Melting of ice

Ice changes from solid to liquid without changing its chemical composition (still $H_2O$). So it is a physical change.

Step4: Classify c. Boiling point of water

Boiling point is a characteristic of water that can be observed without changing water's chemical identity. So it is a physical property.

Step5: Classify d. Baking bread

Ingredients in bread dough undergo chemical reactions to form new substances like carbon dioxide gas (which makes the bread rise). So it is a chemical change.

Step6: Classify e. Dissolving salt in water

Salt dissolves in water, but both salt and water retain their chemical identities. It is a physical change.

Step7: Classify f. Flammability of gasoline

Flammability describes how gasoline can react with oxygen to burn, forming new substances. So it is a chemical property.

Step8: Classify g. Chopping wood

Chopping wood changes its physical form but not its chemical composition. So it is a physical change.

Step9: Classify h. Photosynthesis in plants

Plants use carbon dioxide and water to produce glucose and oxygen, new substances. So it is a chemical change.

Answer:

a. Element
b. Homogeneous mixture
c. Element
d. Heterogeneous mixture
e. Homogeneous mixture
f. Compound
g. Heterogeneous mixture
h. Compound