Chemical Properties

Which procedure would best allow a scientist to observe a chemical property of hydrochloric acid (HCl) solution?

• cooling the HCl solution until it becomes solid, and measuring this temperature

• adding zinc to the HCl solution and observing whether or not bubbles are produced

• placing a conductivity probe into a beaker of HCl solution to determine if it conducts electricity

• measuring the mass of and volume of a sample of HCl solution to find its density

Suppose that a substance in a beaker is heated over a burner in a science lab. Which observation would most likely indicate that a chemical change has occurred in the substance?

• If the substance is a liquid or solid, an increase in temperature would indicate a chemical change.

• If the substance is a liquid, a change of some of the liquid to gaseous form would indicate a chemical change.

• If the substance is a solid, a change of some of the solid to liquid form would indicate a chemical change.

• If the substance is a liquid or solid, production of an odor would indicate a chemical change.

The descriptions below explain two ways that water is used by plants on a sunny day.

I. In a process called transpiration, some liquid water in leaves changes to water vapor. The water vapor is released into the air through tiny pores in the leaves. This allows more liquid water from the soil to be pulled up the roots and stem to replace water lost from the leaves.

II. Plants use some of this water in leaves in a process called photosynthesis. During photosynthesis, water and carbon dioxide break apart and recombine to form two new substances, oxygen and glucose.

Based on the above description of transpiration and photosynthesis, which type of change happens to water during each process?

• In transpiration, because some of its properties change, water undergoes a physical change but keeps its identity. In photosynthesis, because its identity changes, water undergoes a chemical change.

• In transpiration, because some of its properties change, water undergoes a chemical change but keeps its identity. In photosynthesis, because its identity changes, water undergoes a physical change.

• In transpiration, because its physical properties change, water undergoes a physical change and loses its identity. In photosynthesis, because it keeps its identity, water undergoes a chemical change.

• In transpiration, because its chemical properties change, water undergoes a chemical change and loses its identity. In photosynthesis, because it keeps its identity, water undergoes a physical change.

Juan mixed a solid and a liquid together in a beaker. He determined that a chemical change occurred.

If his conclusion is correct, which substances could he have been observing and why?

• ice mixed into warm oil, because the change of state that occurred when the ice melted cannot be reversed

• baking soda mixed into vinegar, because the production of bubbles indicates that a new substance formed

• sugar mixed into hot water, because the disappearance of solid indicates that the chemical identity of the sugar changed

• sand mixed into water, because when sand was added the mass of the beaker increased

Which is an example of a chemical change?

• frying an egg

• boiling water

• melting butter

• chopping onions

During a camping trip, Tiara collected dry branches and broke them into smaller pieces. She then placed the sticks in a fire pit and used a match to light the sticks on fire. Next, she propped a metal pan of water over the fire and heated it until the water boiled.

Which list correctly describes physical and chemical changes that occurred in this scenario?

• physical change: breaking sticks

  chemical changes: lighting the fire, boiling water

• physical change: boiling water

  chemical change: breaking sticks, lighting the fire

• physical changes: lighting the fire, boiling water

  chemical change: breaking sticks

• physical changes: breaking sticks, boiling water

  chemical change: lighting the fire

A scientist is examining an unknown solid. Which procedure would most likely help determine a chemical property of the substance?

• heating it to find the temperature at which it melts

• exposing it to a flame to see if it catches on fire

• hitting it with a hammer to determine if it breaks or bends

• placing it in water to find out whether or not it dissolves

Which characteristic of a substance is considered a chemical property?

• its boiling point

• its reactivity

• its density

• its conductivity

Which statement best describes chemical properties of matter?

• Chemical properties, such as density, must be observed when a substance is in its natural state at room temperature and normal atmospheric pressure.

• Chemical properties, such as reactivity, must be observed when a substance is in its natural state at room temperature and normal atmospheric pressure.

• Chemical properties, such as combustibility, are generally observed as the identity of a substance changes and one or more new substances form.

• Chemical properties, such as boiling point, are generally observed as the identity of a substance changes and one or more new substances form.

Which statement best describes what happens during a chemical change?

• Both the identity and the properties of a substance change.

• Some properties of a substance change, but its identity remains the same.

• The chemical properties of a substance change, but its physical properties remain the same.

• The physical properties of a substance change, but its chemical properties remain the same.