Question

version id: a

1. which of the following is true about compounds?

a. they can be physically separated into their component elements.
b. they have compositions that vary.
c. they are chemically combined from 2 or more elements in definite proportions.
d. they have the same chemical properties as their component elements.
e. they cannot be chemically separated into smaller components.

1. which of the following substances is a mixture?

a. carbon dioxide
b. air
c. iron
d. purified water

1. if a mixture is not uniform throughout, it is called

a. homogeneous.
b. heterogeneous.
c. chemically bonded.
d. a solution.

1. which of the following is true for all chemical reactions?

a. the total mass of the reactants increases.
b. the total mass of the products is greater than the total mass of the reactants.
c. the total mass of the products is less than the total mass of the reactants.
d. the total mass of the reactants equals the total mass of the products.

1. what must occur for a change to be a chemical reaction?

a. there must be a change in composition.
b. there must be a change in physical properties.
c. the change must involve a change in mass.
d. the change must involve a change in volume.

1. which of the following is not a physical property of a substance?

a. color
b. malleability
c. freezing point
d. ability to react with oxygen
e. temperature

1. solid aluminum and liquid bromine combine to form aluminum bromide. aluminum and bromine are called the

a. products.
b. combinators.
c. synthetics.
d. reactants.

1. a chemical change occurs when (select best answer):

a. water is boiled
b. a wax candle melts
c. wood burns in a fire pit
d. an aluminum can is recycled into new aluminum cans

1. an 8.00 g sample of aluminum reacts completely with oxygen to form 15.20 g of aluminum oxide. how many grams of oxygen are used in the reaction?

a. 1.50 g
b. 7.20 g
c. 8.00 g
d. 23.20 g
e. 52.6 g

1. a physical change occurs when a

a. bread loaf on the counter turns moldy.
b. silver bowl tarnishes and turns black.
c. lit candle creates smoke.
d. glue gun melts a glue stick.

1. if a mixture is uniform in composition, it is said to be

a. homogeneous.
b. chemically bonded.
c. heterogeneous.
d. a compound.

1. an example of an extensive property of matter is

a. temperature
b. boiling point
c. mass
d. color
e. density

Explanation:

Step1: Recall compound definition

Compounds are chemically - combined from 2 or more elements in definite proportions.

Step2: Analyze option for mixtures

Air is a mixture of different gases like nitrogen, oxygen etc.

Step3: Define non - uniform mixtures

Non - uniform mixtures are called heterogeneous.

Step4: Apply law of conservation of mass

In a chemical reaction, the total mass of reactants equals the total mass of products.

Step5: Identify chemical reaction criteria

A chemical reaction must have a change in composition.

Step6: Distinguish physical and chemical properties

Ability to react with oxygen is a chemical property.

Step7: Identify reactants in a reaction

In a reaction, starting substances are reactants.

Step8: Differentiate chemical and physical changes

Wood burning is a chemical change, while boiling water, melting wax, and recycling aluminum are physical changes in part.

Step9: Calculate mass of oxygen

Using the law of conservation of mass, mass of oxygen = mass of product - mass of aluminum = 15.20 g - 8.00 g=7.20 g.

Step10: Identify physical change

Melting a glue stick is a physical change.

Step11: Define uniform mixtures

Uniform mixtures are homogeneous.

Step12: Identify extensive property

Mass is an extensive property as it depends on the amount of matter.

Answer:

1. c. They are chemically combined from 2 or more elements in definite proportions.
2. b. air
3. b. heterogeneous
4. d. The total mass of the reactants equals the total mass of the products.
5. a. There must be a change in composition.
6. d. ability to react with oxygen
7. d. reactants
8. c. wood burns in a fire pit
9. b. 7.20 g
10. d. glue gun melts a glue stick.
11. a. homogeneous
12. c. mass