Science Homework Help

1) Which of the following is true of physical properties?

1) 

Physical properties

include mass, color, and flammability.

2) 

Physical properties include density, melting point, and ductility.

3) 

Physical properties describe the potential for the material to undergo a reaction.

4) 

Physical properties cannot be observed without changing the identity of the material.

2) Which answer best completes the following sentence?

_____ is an example of physical change while _____ is an example of a chemical change.

1) 

Freezing water, boiling nitrogen

2) 

Breaking a pencil, rusting of iron

3) 

Burning wood, dissolving salt in water

4) 

Bending a piece of aluminum, condensing water vapor

3) Which of the following is not a physical property of sucrose (table sugar)?

1) 

It tastes sweet.

2) 

It forms a solid white crystal.

3) 

It dissolves easily in warm water.

4) 

It becomes carbon dioxide and water when heated.

4) In an experiment, two clear liquids are combined in a beaker. A white precipitate (solid) forms and the temperature in the beaker rises.

Which of the following best explains what happened?

1) 

The chemical identity of the substances involved was not changed.

2) 

The physical properties of the reactants and products are the same.

3) 

A chemical change took place as indicted by the precipitate and release of heat.

4) 

The physical properties, i.e. density and volume, explain the formation of the solid.

5) What coefficients must be added to balance the following reaction?

_____ Pb + _____ H3PO4  _____ H2 + _____ Pb3(PO4)2

1) 

3, 2, 1, 1

2) 

3, 2, 2, 1

3) 

3, 1, 3, 1

4) 

3, 2, 3, 1

6) Which of the following chemical equations violates the law of conservation of mass?

1) 

Ti + 2Cl2  TiCl4

2) 

2C